New Data on the Skull and Dentition in the Mongolian Late Cretaceous Eutherian Mammal Zalambdalestes

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NEW DATA ON THE SKULL AND DENTITION IN THE MONGOLIAN LATE CRETACEOUS EUTHERIAN MAMMAL ZALAMBDALESTES

JOHN R. WIBLE Section of Mammals, Carnegie Museum of Natural History, 5800 Baum Boulevard, Pittsburgh, PA 15206 e-mail: [email protected]

MICHAEL J. NOVACEK Division of Paleontology, American Museum of Natural History e-mail: [email protected]

GUILLERMO W. ROUGIER Department of Anatomical Sciences and Neurobiology, School of Medicine, University of Louisville, Louisville, KY 40292 e-mail: [email protected]

BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024 Number 281, 144 pp., 58 ®gures, 3 tables Issued January 9, 2004

CONTENTS Abstract ...... 3 Introduction ...... 3 Materials and Methods ...... 5 History of Investigations ...... 7 Comparative Morphology ...... 17 Dentition ...... 17 Upper Incisors ...... 18 Upper Canine ...... 21 Upper Premolars ...... 22 Upper Molars ...... 25 Lower Incisors and Canine ...... 28 Lower Premolars ...... 31 Lower Molars ...... 32 Dental Formula ...... 32 Lower Jaw ...... 33 Skull ...... 37 Nasal-Facial Region ...... 39 Palate ...... 42 Orbitotemporal Region ...... 47 Basicranium and Auditory Region ...... 65 Occiput ...... 84 Endocranial Cast ...... 86 Vascular Reconstruction ...... 88 Veins ...... 90 Arteries ...... 91 Discussion ...... 96 Previous Phylogenetic Analyses ...... 96 Hu (1993) ...... 96 Archibald (1996) and Nessov et al. (1998) ...... 97 Rougier et al. (1998) ...... 99 Meng and Wyss (2001) ...... 103 Archibald et al. (2001) ...... 106 Ji et al. (2002) ...... 109 Comparisons ...... 112 Within Zalambdalestes ...... 112 With Barunlestes butleri ...... 114 With Kulbeckia kulbecke ...... 116 With Leptictids and Insectivorans ...... 118 With Rodents, Lagomorphs, and Elephant Shrews ...... 120 With Asioryctitheres ...... 124 With Zhelestids ...... 129 Conclusions ...... 129 Acknowledgments ...... 131 References ...... 131 Addendum ...... 140 Appendix 1: List of Anatomical Terms ...... 141 2004 WIBLE ET AL.: ZALAMBDALESTES 3

ABSTRACT Exquisitely preserved specimens of the Late Cretaceous eutherian Zalambdalestes recently collected from the Djadokhta Formation (Early Campanian) of the Gobi Desert by the Mon- golian Academy of Sciences±American Museum of Natural History Expeditions are the cen- terpiece of a thorough redescription of this taxon's craniodental morphology. Resolved and amended are uncertainties and errors in prior descriptions based on poorer preserved specimens collected by earlier expeditions to the Gobi. Preserved and described for the ®rst time in Zalambdalestes is the basicranium, including an ectotympanic bone and portions of the hyoid arch. Zalambdalestes with a skull length of nearly 50 mm is large compared with other Cretaceous eutherians. It is also highly specialized with a long, thin, tubular snout, large diastemata in the anterior upper dentition, and an elongated mesial lower incisor with restricted enamel. These specializations, though less extreme, are also present in the zalambdalestids Barunlestes from the slightly younger Barun Goyot Formation of the Gobi and Kulbeckia from the late Turonian and Coniacian of Uzbekistan and the Santonian of Tadjikistan. No phylogenetic analysis published to date includes enough taxonomic and morphological breadth to evaluate the relationships of Zalambdalestes. Nevertheless, we investigate the impact of our observations on seven phylogenetic analyses published since 1993 that include Zalambdalestes. A comprehensive phylogenetic analysis testing the relationships of Zalamb- dalestes is not included here, but it is expected to result from our ongoing efforts to produce a phylogeny of basal tribosphenic and therian mammals. Currently, zalambdalestids are viewed either as stem eutherians or as having af®nities to Glires (lagomorphs and rodents). Our comparisons with other extinct and extant taxa support a position for Zalambdalestes within Eutheria but outside the crown-group Placentalia. Sup- porting this basal position for Zalambdalestes are such primitive features as the last upper incisor in the maxilla, nasals broadly expanded posteriorly to contact the lacrimals, pterygoids meeting on the midline, and the position of the glenoid fossa on the zygoma and not the braincase proper, in addition to the occurrence of epipubic bones reported previously. Za- lambdalestes shares a number of apomorphies with Asioryctitheria, the clade including the Mongolian Late Cretaceous Asioryctes, Ukhaatherium, and Kennalestes. Among the unusual specializations supporting a zalambdalestid-asioryctithere clade are: the postglenoid foramen anterior rather than posterior to the postglenoid process; the postglenoid and entoglenoid processes of the squamosal continuous; a fusiform ectotympanic expanded laterally and contacting the entoglenoid process; a suprameatal foramen in the squamosal; a crista interfenestralis connecting from the petrosal promontorium to a ®ngerlike tympanic process behind the round window; a large piriform fenestra in the anterior roof of the tympanic cavity, which transmitted the ramus inferior of the stapedial artery endocranially to the orbit; a foramen ovale between the alisphenoid and squamosal; and a medially positioned internal carotid artery. All but the last two of these specializations are reminiscent of those occurring in various extant lipotyphlans, including taxa placed by recent DNA sequence analyses within Afrotheria and Eulipo- typhla, and may provide a link between the Mongolian Cretaceous eutherians and lipotyphlans. The available sample of Zalambdalestes exhibits a remarkable degree of individual variation, including the incidence of the upper maxillary incisor, the ®rst upper premolar, and the second lower premolar. The possibility exists that more than a single species, Z. lechei,is represented.

INTRODUCTION etons occur in the Upper Cretaceous se- Therian mammals are known from Lower quences of the Gobi Desert in Mongolia. Cretaceous deposits by isolated teeth, jaw These fossil beds were ®rst discovered in the fragments, and petrosals (Slaughter, 1965, 1920s by the American Museum of Natural 1971; Kielan-Jaworowska and Dashzeveg, History Central Asiatic Expeditions (CAE) 1989; Cifelli, 1993, 1999; Wible et al., 1997, led by Roy Chapman Andrews (Gregory and 2001) and now by a nearly complete skeleton Simpson, 1926a, 1926b; Simpson, 1928a, with crushed skull (Ji et al., 2002). However, 1928b). The specimens collected were re- the oldest, nearly complete skulls and skel- ferred by Gregory and Simpson (1926a) to 4 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 two new families of Insectivora, the Delta- high in the quality of representative material. theridiidae, including Deltatheridium, Delta- This is largely due to new specimens of Za- theroides, and Hyotheridium, and the Za- lambdalestes and the closely related genus lambdalestidae, including Zalambdalestes. Barunlestes recovered by the Polish±Mon- Of these, Deltatheridium and Deltatheroides golian Expeditions between 1963 and 1971 have been subsequently designated informal- (Kielan-Jaworowska, 1969a, 1975a, 1984a, ly as ``Theria of metatherian-eutherian 1984b, 1984c) and the Soviet±Mongolian grade'' (Butler and Kielan-Jaworowska, Expeditions of 1974 and 1978 (Kielan-Ja- 1973), as a separate order of Theria, incertae worowska and Tro®mov, 1980, 1981). Even sedis (Kielan-Jaworowska, 1982, 1984c), or better preserved skulls of Zalambdalestes a subgroup of Metatheria (Kielan-Jaworow- have been recovered by the Mongolian ska and Nessov, 1990; Rougier et al., 1998; Academy of Sciences±American Museum of Kielan-Jaworowska et al., 2000). Hyotheri- Natural History Expeditions (MAE) in 1995 dium is a poorly preserved taxon with a frag- from the Flaming Cliffs (Bayn Dzak) locality mentary skull and lower jaws (Gregory and of the Djadokhta Formation, where the ho- Simpson, 1926a). Its af®nities are uncertain; lotype was ®rst discovered, and in 1991 from for example, its alleged association with Del- Tugrugeen Shireh, an exposure of the Dja- tatheridiidae (Gregory and Simpson, 1926a) dokhta Formation about 30 km west of Bayn is dubious, because its molar structure, albeit Dzak (®gs. 2, 3). Based on comparisons with poorly preserved, does not resemble the North American vertebrate faunas, the Dja- characteristic triangular upper molar mor- dokhta Formation is thought to be of early phology of the latter. Zalambdalestes has Campanian age (Jerzykiewicz et al., 1993; been subsequently linked with various early Dashzeveg et al., 1995; Rougier et al., 1997; Tertiary Asian groups, such as the Pseudic- Averianov, 1997), although age assignment topidae, Anagalidae, and Eurymylidae, the is not well supported by marine correlation closest living relatives of which are lago- with independent evidence. The two MAE morphs (Van Valen, 1964; Szalay and Mc- specimens are nearly complete crania with Kenna, 1971; McKenna, 1975), rodents dentitions referable to Z. lechei; the lower (Archibald et al., 2001), and elephant shrews jaws are missing in the former (PSS-MAE (Novacek, 1986a; McKenna and Bell, 1997). 130) and are in articulation in the latter (PSS- Alternatively, Zalambdalestes has been given MAE 108). Postcranial material associated a very noncommittal status as Proteutheria, with the specimens includes only a partial incertae sedis (Kielan-Jaworowska et al., innominate (PSS-MAE 108). Other partial 1979), with the added notion that many of skulls with articulated lower jaws (PSS-MAE its skeletal features resemble, in a convergent 129) were collected in 1994 from Bayn Dzak fashion, modern, cursorial or saltatorial ele- and in 1991 from Tugrugeen Shireh (PSS- phant shrews. Epipubic bones, which are MAE 135). Several other specimens refer- widely distributed in eutherian outgroups, able to Zalambdalestes were found in the occur in zalambdalestids (Kielan-Jaworow- new, very rich Upper Cretaceous locality of ska, 1975a; Novacek et al., 1997), suggesting Ukhaa Tolgod (Dashzeveg et al., 1995), but a phylogenetic position basal to living pla- these are currently undergoing preparation. centals (Novacek, 1997). One specimen (cf. Zalambdalestes sp., PSS- Among the therians originally described MAE 131) from Zos Wash, a locality near by Gregory and Simpson (1926a: 3), Za- Ukhaa Tolgod, preserves much of the post- lambdalestes was recognized as ``incompa- cranium, including the left epipubic bone, rably the best known of all Mesozoic mam- and has been ®gured elsewhere (Novacek et mals, every main part of the skull being al., 1997). In the current paper, we describe known although some features are still rather aspects of cranial structure based on PSS- obscure'' (®g. 1). Subsequently, a large num- MAE 108, 130, and other newly recovered ber of excellent Mesozoic mammal skulls specimens, as well as reconsidering previ- and skeletons have come to light (Lillegrav- ously published material, to clarify and ex- en et al., 1979; Novacek, 1992, 1993; Luo et pand on some of the important anatomical al., 2002), but Zalambdalestes still ranks features of this group. 2004 WIBLE ET AL.: ZALAMBDALESTES 5

MATERIALS AND METHODS (1) PSS-MAE 129 (®gs. 21, 31, 39, 41): Partial skull with attached lower jaws col- More that 20 specimens of Zalambdalestes lected from Bayn Dzak on July 3, 1994. The are now known from the collections made by partial skull preserves the snout back to the the MAE, CAE, the Polish±Mongolian Ex- midorbital region, as well as part of the right peditions, and the Soviet±Mongolian Expe- petrosal bone. The right lower jaw lacks the ditions. The varying states of completeness anterior dentition and the angular region; the and preservation of these specimens compli- left lower jaw lacks the anterior dentition and cate comparisons. Our analysis reveals sur- most of the ramus. The preserved posterior prising differences in dental formulae within dentition in both upper and lower jaws is se- this sample (Wible et al., 1998), yet other verely worn. In the craniodental measure- features that can be compared (e.g., tooth ments that can be made (see tables 2 and 3), size and shape, skull proportions) appear PSS-MAE 129 resembles other specimens fairly homogenous. Intraspeci®c dental referred to Zalambdalestes lechei with one anomalies reported for extant mammals in- striking exception: the diastema between I2 clude differences in tooth number (for recent and C is just slightly more than half that in discussion and extensive literature, see PSS-MAE 108 and 130. Because of this dif- Gould, 1997, 2001). Therefore, until more ference, we refer PSS-MAE 129 to cf. Za- material is known facilitating taxonomic re- lambdalestes sp. vision, we refer the following three MAE (2) PSS-MAE 131: Articulated skeleton specimens to Z. lechei. and skull with attached lower jaws collected (1) PSS-MAE 108 (®g. 2): Skull with at- from Zos Wash near Ukhaa Tolgod on July tached lower jaws and four cervical vertebrae 15, 1996. The skull and lower jaws have not obscuring much of the palate and occiput, been removed from the block containing the respectively, and partial innominate collected skeleton, and only their left sides are ex- from Tugrugeen Shireh in 1991. Zygomatic posed. The skull requires additional prepa- arches are incomplete and the crowns of the ration, and only the anterior dentition is con- right mandibular anterior dentition (i1-p2) sidered here. The skeleton is under study are broken off. Right basicranium is incom- (Horovitz et al., 1998; Horovitz, 2000). No- pletely prepared to buttress the well-pre- vacek et al. (1997: ®gs. 3, 4) illustrated the served ectotympanic bone found in what ap- entire specimen, including an enlargement of pears to be its proper anatomical position. the pelvis, and referred it to cf. Zalambda- (2) PSS-MAE 130 (®g. 3): Skull collected lestes. We have no grounds for amending from Bayn Dzak in 1995. The right zygo- their identi®cation, given that the skull of matic arch and premaxilla are incomplete; this specimen has not been further prepared. the lower jaws are unknown. The braincase (3) PSS-MAE 145: Skull with attached roof is incomplete, exposing areas of the en- lower jaws, fragmentary pectoral girdle, and docranial cast. nearly complete posterior half of the skeleton (3) PSS-MAE 135 (®gs. 20, 30, 38): Par- collected from Tugrugeen Shireh in 2000. tial skull with attached partial lower jaws Skull length is greater than 60 mm, roughly collected from Tugrugeen Shireh in 1991. 25% more than any other Zalambalestes. The The zygomatic arches are incomplete. Miss- specimen is in the early stages of preparation, ing are the snout anterior to the third pre- and until more is uncovered for study, we molars and the body of the mandible, al- refer it to cf. Zalambdalestes sp. The only though the crowns of some of the lower post- observations that are made in this report con- canine teeth are preserved. Only the skull cern the anterior dentition. roof and orbitotemporal regions have been To assess previous hypotheses of the lower partially prepared. The block also contains and higher level relationships of Zalambda- some broken postcranial remains, including lestes, comparisons of the MAE specimens the head of the humerus. are made with other Zalambdalestes as well Also discussed here are the following as with other relevant extinct and extant taxa. three specimens that are referred to cf. Za- We studied the four AMNH specimens of lambdalestes sp. Zalambdalestes (21704, 21707, 21708, 6 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

21709). We also had the opportunity to study na, 1975; Novacek, 1986b; Rougier et al., the cataloged collections of Zalambdalestes 1998; Ji et al., 2002), with the most likely housed at the Polish and Russian Academy transformation to the four premolars of many of Sciences. Unfortunately, however, our vis- extant placentals involving the loss of a pre- it to Warsaw came at an early stage in the molar in the middle of the series. Despite preparation of this monograph and those this, we do not alter our numeration of pre- specimens should be restudied in light of our molars in Zalambdalestes, because as yet results. For comparisons with other taxa, we there is no speci®c evidence for the loss of excluded ausktribosphenids from the Early a ®fth premolar in zalambdalestids that might Cretaceous of Australia, because of the con- indicate the position of the lost tooth. tinuing controversy surrounding the af®nities As is the case with terminology, morphol- of this group. Some authors (e.g., Rich et al., ogists also do not employ a standard set of 1997, 1999, 2001, 2002) consider ausktri- craniodental measurements. The dental and bosphenids to be possible eutherians, where- craniomandibular measurements taken by us as others (e.g., Luo et al., 2001, 2002) sup- are listed in tables 2 and 3 and illustrated in port monotreme af®nities. ®gures 6 and 16, respectively. We follow Ar- Unfortunately, morphologists studying dif- chibald (1982) for the former and Musser et ferent lineages of extinct and extant mam- al. (1998) for the latter. mals do not employ a common terminology High-resolution CT scans of PSS-MAE for the description of anatomical features. 108 and 130 were made at the High Reso- The reasons for this are many, but largely are lution X-ray Computed Tomography Facility the result of history, unresolved homologies, at the Department of Geological Sciences of and lack of unifying studies tackling a broad the University of Texas at Austin. The de- enough set of taxa to trace transformations scription and analyses of these scans will be among disparate forms. Providing a standard the subject of a subsequent publication. We language is a worthwhile goal but is beyond make some reference to these scans here per- the scope of the present work. As a step in tinent to particular anatomical features. that direction, we have included in appendix 1 a chart detailing the sources for the non- INSTITUTIONAL AND EXPEDITION dental anatomical terms used. Whenever pos- ABBREVIATIONS sible, we have opted for the Latin term (or anglicized version thereof) from the fourth AMNH Department of Vertebrate Paleontology, edition of the Nomina Anatomica Veterinaria American Museum of Natural History (1994). For dental terminology (®g. 5), we CAE Central Asiatic Expeditions follow Reig et al. (1987) and Nessov et al. CM Section of Mammals, Carnegie Muse- (1998). The abbreviations ``I, C, P, M'' and um of Natural History, Pittsburgh ``i, c, p, m'' are used to refer to upper and CM-VP Section of Vertebrate Paleontology, Carnegie Museum of Natural History, lower incisors, canines, premolars, and mo- Pittsburgh lars, respectively. Our numeration of incisors MAE Mongolian Academy of Sciences± is based solely on position within the jaw and American Museum of Natural History does not attempt to account for changes from Expeditions an ancestral condition with more teeth or to OMNH Oklahoma Museum of Natural History, imply homology of the same positional ele- University of Oklahoma, Norman ments in other eutherian taxa. The same is PIN Institute of Paleontology, Academy of true for premolars (see below), except that Sciences, Moscow here our numeration takes into account the PSS Paleontological and Stratigraphy Sec- absence of particular premolars in some tion (Geological Institute), Mongolian specimens of Zalambdalestes. A list of ana- Academy of Sciences, Ulaan Baatar URBAC Uzbekian/Russian/British/American/ tomical abbreviations employed in the ®g- Canadian Joint Paleontological Expe- ures is given in table 1. dition, Kyzylkum Desert, Uzbekistan, Regarding the numeration of premolars, specimens in the Institute of Zoology, more evidence is accumulating that eutheri- Tashkent, and the Royal Ontario Mu- ans primitively had ®ve premolars (McKen- seum, Toronto 2004 WIBLE ET AL.: ZALAMBDALESTES 7

ZPAL MgM Institute of Paleobiology, Polish upper jaw, and a long, tubular snout region, Academy of Sciences, Warsaw bent somewhat downward. Simpson (1928b) reevaluated the af®nities HISTORY OF INVESTIGATIONS of Zalambdalestes, chie¯y from the im- proved knowledge of molar morphology pre- Gregory and Simpson (1926a) recognized served in Z. grangeri (AMNH 21709). He a new monotypic family Zalambdalestidae noted that the points of resemblance in the comprising the genus and species Zalamb- dentition and osteology between Zalambda- dalestes lechei. To this species they referred lestes and ``zalambdodonts'' were likely three specimensÐthe type skull (AMNH primitive for insectivorans in general. In con- 21708; ®gs. 1, 12, 13), a younger skull trast, the molar structure of Zalambdalestes (AMNH 21704), and a lower jaw with p3± ``points much more de®nitely toward the er- 4, m1±3 (AMNH 21707). Later, Simpson inaceomorphs'' (Simpson, 1928b: 3), being (1928a) described a new species, Z. grangeri, built on the same groundplan as leptictids. from material revealed by further preparation He proposed that Zalambdalestes was closer of nodules collected in the 1925 CAE expe- to leptictids, whereas ``zalambdodonts'' were dition. The single specimen (AMNH 21709) derived from a group closer to the Mongolian included a partial anterior skull with a nearly Late Cretaceous Deltatheridiidae. Simpson complete right maxilla with cheekteeth as (1945) formalized these af®nities in his clas- well as a partial pelvis and femur. Simpson si®cation of mammals, allocating the Za- (1928a: 2) noted only subtle differences be- lambdalestidae and Leptictidae to the Erina- tween Z. grangeri and Z. lechei (``molars are ceoidea. Close relationships between zalamb- more robust and longer than their widths''). dalestids and leptictids were supported sub- Expectedly, a case for synonymy of Z. gran- sequently by McDowell (1958), Van Valen geri with Z. lechei has been made (Szalay (1967), Kielan-Jaworowska (1969a), and and McKenna, 1971) and followed by sub- Clemens (1973). sequent authors. Chow (1953) compared Zalambdalestes to Zalambdalestidae was originally distin- Endotherium, an enigmatic form described guished by its highly transverse upper molars by Shikama (1947) from what was thought with closely appressed metacones and para- by Chow (1953) to be the Early Cretaceous cones, as well as by lack of hypocones, mo- of Manchuria. Chow (1953: 156) proposed lariform last premolar, and very narrow in- that ``the specimen of Endotherium belongs terdental embrasures (Gregory and Simpson, undoubtedly to that of a primitive insectivore 1926a: 14). A resemblance with the V- closely related to the genus Zalambdalestes.'' shaped (zalambdodont) upper molar cusp Unfortunately, the illustrations of the teeth of pattern of ``zalambdodont'' insectivorans Endotherium ``are less than adequate line (represented by living tenrecs, golden moles, drawings, the descriptions are not diagnostic; and the Antillean Solenodon) was noted, and the specimens are now lost'' (Clemens with the proposal that zalambdalestids rep- et al., 1979: 28). McKenna and Bell (1997) resented a ``stem group of the zalambdodont identi®ed Endotherium as a basal therian. stock possibly at a time before it separated Van Valen (1964: ®g. 2) presented a new from the leptictid branch'' (Gregory and restoration of the skull of Zalambdalestes in Simpson, 1926a: 14). Simpson (1928a) ob- lateral view and of the palate, redrawn here served that the large iliac crest in Zalamb- as ®gure 4A and C. He noted resemblances dalestes (AMNH 21709) was more reminis- in the cheekteeth between Zalambdalestes cent of creodonts than insectivorans, but, on and two forms from the late Paleocene Gash- the whole, the partial femur and innominate ato Formation of Mongolia, Pseudictops and were of a structure expected by this author Eurymylus, the latter identi®ed as the oldest in primitive eutherian mammals. Gregory lagomorph, although subsequent work has and Simpson (1926a) also noted some pe- placed it nearer rodents (Li and Ting, 1985; culiar features of Zalambdalestes. These in- Meng et al., 1994; Meng and Wyss, 2001) or cluded greatly elongated procumbent lower outside both rodents and lagomorphs (Dash- incisors, long postcanine diastemata in the zeveg et al., 1998). A tentative phylogeny 8 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

TABLE 1 List of Anatomical Abbreviations 2004 WIBLE ET AL.: ZALAMBDALESTES 9

TABLE 1 (Continued) 10 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 1. The skull of the holotype of Zalambdalestes lechei AMNH 21708 in (clockwise from upper left) dorsal, ventral, and right lateral views. identi®ed Eurymylus (and true lagomorphs) (Van Valen, 1964: 490). Building on Van and Pseudictops (and anagalids) as sister Valen's (1964) observations, Szalay and Mc- groups, with Zalambdalestes as an outgroup. Kenna (1971: 301) erected a new order, An- This lineage was said ``to have originated agalida, to include ``the mammalian families near a Late Cretaceous leptictid insectivore'' Zalambdalestidae, Pseudictopidae, Anagali- 2004 WIBLE ET AL.: ZALAMBDALESTES 11

Fig. 2. The skull and lower jaws of Zalambdalestes lechei PSS-MAE 108 in (clockwise from upper left) dorsal, ventral, left lateral, and right lateral views. 12 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 3. The skull and lower jaws of Zalambdalestes lechei PSS-MAE 130 in (clockwise from upper left) dorsal, ventral, left lateral, and right lateral views. 2004 WIBLE ET AL.: ZALAMBDALESTES 13

Fig. 4. Reconstructions of the skull of Zalambdalestes lechei in right lateral views (A, B) and in ventral views (C, D). Panels A and C are redrawn from Van Valen (1964: ®g. 2), B is from Kielan- Jaworowska (1975a: ®g. 2A), and D is from Kielan-Jaworowska (1984a: ®g. 1). The basicranium in the last is based on Barunlestes butleri. 14 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 dae, and Eurymylidae as members of an en- Also in the collections of the Polish±Mon- demic Cretaceous and early Tertiary Asian golian Expeditions was a second genus of radiation, whose closest living relatives are Zalambdalestidae, Barunlestes (Kielan-Ja- the Lagomorpha.'' Added to Anagalida were worowska, 1975a). The single species B. but- macroscelideans or elephant shrews by Mc- leri is known from six specimens housed in Kenna (1975) and rodents by Novacek Warsaw, two of which include some postcra- (1986a). nial elements, and one specimen housed in In the same paper naming Anagalida, Sza- Moscow (Kielan-Jaworowska, 1975a, 1978; lay and McKenna (1971) re®gured three of Kielan-Jaworowska and Tro®mov, 1980; the four AMNH specimens of Zalambdales- Fostowicz-Frelik and Kielan-Jaworowska, tes (21707, 21708, and 21709). They noted 2002). An eighth specimen, ZPAL MgM-I/ several details of the dentition revealed 135, was originally considered to be Barun- through additional cleaning and argued that lestes by Kielan-Jaworowska and Tro®mov all four specimens be referred to one species, (1980), but it may be a new genus related to Z. lechei. To the Zalambdalestidae, they also eurymylids (Li and Ting, 1985; Fostowicz- referred Praolestes nanus, a lower jaw frag- Frelik and Kielan-Jaworowska, 2002). The ment with three postcanine teeth (AMNH seven specimens of Barunlestes were col- 21718) from the Gashato Formation. How- lected from the Barun Goyot Formation or ever, Kielan-Jaworowska (1984a) denied this its equivalents, either from the Nemegt Basin referral, because P. nanus does not exhibit or Khermeen Tsav. The Barun Goyot For- the zalambdalestid trend of having the molar mation has been considered to be slightly trigonids reduced in length with regard to the younger than the Djadokhta (GradzinÂski et talonids. P. nanus was originally described al., 1977), but the vertebrate assemblages as a possible leptictid by Matthew et al. from these units are more similar than pre- (1929), later identi®ed as a geolabidine adap- viously held (Novacek et al., 1996). B. but- isoricid by Van Valen (1967), and most re- leri differs from Zalambdalestes in having a cently treated as Leptictida, incertae sedis by shorter, but somewhat more robust skull, a McKenna and Bell (1997). reduced, single-rooted upper canine (double- Kielan-Jaworowska (1969a) published the rooted in Zalambdalestes), deeper dentary, ®rst in a series of descriptive papers on za- and higher coronoid process with a powerful lambdalestid material from the collections of coronoid crest (Kielan-Jaworowska, 1975a, the Polish±Mongolian Expeditions housed in 1984a; Kielan-Jaworowska and Tro®mov, Warsaw. In all, twelve specimens of Zalamb- 1980). The skull of B. butleri has been re- dalestes, including two known from some constructed in lateral view (Kielan-Jawo- postcrania (Kielan-Jaworowska, 1978), were rowska, 1975a: ®g. 2B; Kielan-Jaworwoska collected at the Djadokhta Formation site of et al., 1979: ®g. 12±1D), redrawn here as ®g- Bayn Dzak (Kielan-Jaworowska, 1984a). ure 51B, and the braincase in lateral and ven- Kielan-Jaworowska (1969a) initially identi- tral views (Kielan-Jaworowska and Tro®- ®ed two of the twelve specimens as Z. gran- mov, 1980: ®gs. 1, 2). geri and one as Zalambdalestes sp., but fol- The zalambdalestid specimens housed in lowing Szalay and McKenna (1971), she lat- Warsaw and Moscow have considerably ex- er (Kielan-Jaworowska et al., 1979, 2000; panded information on the group's morphol- Kielan-Jaworowska, 1984a) referred these to ogy and variation (Kielan-Jaworowska, Z. lechei. An additional specimen of Z. lechei 1969a, 1975a, 1975b, 1978, 1984a, 1984b, collected from Tugrugeen Shireh by the So- 1984c; Crompton and Kielan-Jaworowska, viet±Mongolian Expeditions in 1978 is 1978; Kielan-Jaworowska and Tro®mov, housed in the Institute of Paleontology, Mos- 1980, 1981; Fostowicz-Frelik and Kielan-Ja- cow (Kielan-Jaworowska and Tro®mov, worowska, 2002). Notable among these dis- 1981). The skull of Z. lechei has been recon- closures was evidence for distinctive postcra- structed in lateral and ventral view by Kie- nial specializations, including hindlimb elon- lan-Jaworowska (1975a: ®g. 2A, 1984a: ®g. gation, extensive fusion of the tibia and ®b- 1; Kielan-Jaworowska et al., 1979: ®g. 12± ula, and very long metatarsals. From these 1C), redrawn here as ®gure 4B and D. and related features, Kielan-Jaworowska 2004 WIBLE ET AL.: ZALAMBDALESTES 15

(1984c: 180) concluded that ``the locomotion lestids resemble, in a convergent fashion, of Zalambdalestidae was similar to that in modern cursorial or saltatorial macrosceli- present-day Macroscelididae.'' In this she deans. Subsequently, Kielan-Jaworowska suggested a cursorial or hopping mode more (1984c) suggested that zalambdalestids share compatible with certain small mammals in a common ancestry with two other Mongo- semi-desert habitats. Lithology and preser- lian Late Cretaceous forms, Kennalestes and vation of fossils in the Upper Cretaceous red Asioryctes (®g. 51D, E), and that Prokenna- or white sandstones of the Djadokhta or Ba- lestes (Kielan-Jaworowska and Dashzeveg, run Goyot Formations do suggest arid to 1989) from the Early Cretaceous Mongolian semi-arid conditions (GradzinÂski et al., 1977; locality Khoobur represents a likely ancestor Jerzykiewicz et al., 1993; Dashzeveg et al., for these taxa. 1995; Loope et al., 1998). Several other Asian Cretaceous zalamb- Another postcranial feature of interest was dalestids have been identi®ed by Nessov and cited by Kielan-Jaworowska (1975b) in the co-workers. Kulbeckia kulbecke from Uzbek- holotype of Barunlestes (ZPAL MgM-1/77). istan was originally assigned by Nessov Here the innominate showed a thickened and (1993) to the monotypic Kulbeckiidae within roughened area on the anterior surface of the Mixotheridia, which also included Zhelesti- ilio-pubic moiety. This Kielan-Jaworowska dae and Zalambdalestidae. Nessov (1997) interpreted as the attachment site for the epi- later referred Kulbeckiidae to Zalambdales- pubic bone, previously unknown in eutheri- toidea within Mixotheridia. Recently, Archi- ans. Although the bone itself was not iden- bald and co-authors (Archibald et al., 2001; ti®ed in the specimen, it was apparent that Archibald and Averianov, 2003) have re- the con®guration of the anterior pubis closely viewed all the known Kulbeckia specimens, resembles the marsupial condition (Elftman, from the late Turonian and Coniacian of Uz- 1929; Reilly and White, 2003). In addition bekistan, including the left side of a skull to marsupials, paired epipubic bones occur in from the snout to the midorbit (®gs. 51C, monotremes (Grif®ths, 1978), multitubercu- 52), and the Santonian of Tadjikistan. We lates (Kielan-Jaworowska, 1969b, 1979), the agree with these authors' assignment of Kul- triconodont Jeholodens (Ji et al., 1999), the beckia to Zalambdalestidae, because it shares symmetrodont Zhangeotherium (Hu et al., with Zalambdalestes and Barunlestes, among 1997), the dryolestoid Henkelotherium other traits, an elongated snout, procumbent, (Krebs, 1991), the prototribosphenidan Vin- enlarged medial lower incisor, and antero- celestes (Rougier, 1993), the basal eutherian posteriorly compressed molar trigonids. Eomaia (Ji et al., 2002), and the asiorycti- Alymlestes kielanae Averianov and Nessov, there Ukhaatherium (Novacek et al., 1997), 1995 is represented by the crown of a left and are likely a primitive condition for mam- lower molar (m1?) from the Campanian of mals. Substantiating Kielan-Jaworowska's the Alymtau Range in southern Kazakhstan (1975b) prediction that epipubics occur in (see also Nessov et al., 1994). It resembles zalambdalestids, a left epipubic was discov- Zalambdalestes, Barunlestes, and Kulbeckia ered in the skeleton of cf. Zalambdalestes sp. in most features (e.g., anteroposteriorly (PSS-MAE 131) collected near Ukhaa Tol- shortened trigonid, strongly basined talonid), god (Novacek et al., 1997) and supports the and we agree its assignment to Zalambdales- basal position of zalambdalestids among eu- tidae seems reasonable (see also McKenna therians, probably outside the crown-group and Bell, 1997; Archibald and Averianov, Placentalia (Novacek, 1997). 2003). Two additional specimens from the Despite a number of specializations, in- locality yielding A. kielanae were described cluding greatly enlarged lower ®rst incisors by Averianov (1997) as ?Alymlestes, a frag- and elongated, cursorially designed hind- ment of right lower jaw with p2±3 and a de- limbs, Zalambdalestes and Barunlestes were ciduous right p3?; the attribution of the latter given a very noncommittal status as Prot- is not defensible. As noted by Averianov and eutheria, incertae sedis by Kielan-Jaworow- Nessov (1995) and Archibald and Averianov ska et al. (1979), with the added notion that (2003), the lower molar of Alymlestes ap- many of the skeletal features of zalambda- pears to be more derived than the remaining 16 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 zalambdalestids in having a taller trigonid and reassigned it to the Tillodontia (see also and talonid and a more reduced paraconid. McKenna and Bell, 1997). Other taxa referred to Zalambdalestidae by The most recent views on the relationships Nessov and co-workers include Daulestes of Zalambdalestidae include the following kulbeckensis Tro®mov and Nessov, 1979 in four, none of which are supported by broad- Nessov and Tro®mov (1979) from the late scale phylogenetic analysis that samples all Turonian (Coniacian according to McKenna (or even most) relevant taxa or morphologi- et al., 2000) of the central Kyzylkum Desert, cal information. Van Valen's (1964) hypoth- Uzbekistan, represented by a fragmentary esis of af®nities with lagomorphs is support- right lower jaw with incomplete dentition. Its ed by Averianov (2000). He noted (p. 648) assignment to the Zalambdalestidae was only that ``the molar of Alymlestes is very close provisionally recognized by Kielan-Jawo- to the initial condition of Lagomorpha. Pos- rowska (1984a); Nessov (1982, 1987) and sibly, zalambdalestids were a more numerous Nessov et al. (1994) transferred it to the Pa- and diverse group than previously thought, laeoryctidae. A new species of Daulestes, D. based on the Mongolian genera, and some nessovi, represented by a partial skull (®g. members were close to the ancestral stock for 51F) is most similar to asioryctids (McKenna Lagomorpha and Glires.'' Glires af®nities for et al., 2000) and is assigned tentatively by zalambdalestids has been supported most re- these authors to Asioryctitheria, which in- cently by Archibald et al. (2001) in their phy- cludes the asioryctids Asioryctes and logenetic analysis of well-described Late Ukhaatherium, and Kennalestes (Novacek et Cretaceous eutherians along with two archaic al., 1997). Beleutinus orlovi Bazhanov, 1972 representatives from both Ungulata and Gli- represented by a fragmentary right lower jaw res. Results of this analysis did not identify with broken molar crowns from the Santon- a monophyletic Zalambdalestidae, but placed ian of the Kzyl-Orda District of Kazakhstan Kulbeckia kulbecke, Zalambdalestes lechei, was tentatively referred to Zalambdalestidae and Barunlestes butleri as successive out- by Nessov (1987) and Nessov et al. (1994). groups to the stem Glires taxa Mimotona and This assignment is unwarranted in light of Tribosphenomys (®g. 49C). Other authors the fragmentary nature of the specimen (see group zalambdalestids with various other also Kielan-Jaworowska et al., 1979; Clem- Asian Cretaceous taxa. Nessov (1985a) ens and Lillegraven, 1986). Finally, a new, erected a new proteutherian suborder Mix- referred species of Zalambdalestes, Z. myn- otheridia to include the Cretaceous Uzbeki- bulakensis Nessov, 1985b from the Conia- stan forms Aspanlestes, Taslestes, and Sor- cian of the central Kyzylkum Desert, Uzbek- lestes, the North American Campanian genus istan, is represented by a fragmentary left Gallolestes, and probably Zalambdalestidae. lower jaw with m2 (see also Nessov and Kie- Added to Mixotheridia were Zhelestes from lan-Jaworowska, 1991: ®g. 1). However, it the Coniacian of Uzbekistan and possibly was considered by Nessov et al. (1994), and Tupaiidae by Nessov et al. (1994). The recent we concur, to be a junior synonym of Sor- phylogenetic analyses by Archibald (1996), lestes budan, a member of the ``Zhelesti- Nessov et al. (1998), and Archibald et al. dae'', the paraphyletic group of Asian Cre- (2001) do not support Mixotheridia; zalamb- taceous taxa said to be related to ungulates dalestids do not group with the remaining (Archibald, 1996; Nessov et al., 1998). Cretaceous ``mixotheridians'', which are A ®nal taxon referred to Zalambdalestidae placed as the stem group to Ungulata (®gs. is Anchilestes impolitus from the Paleocene 46A, C, 49A, C). Novacek et al. (1997) of Qianshan Basin, Anhui, China (Chiu and named a new taxon Asioryctitheria to in- Li, 1977). The original description, in Chi- clude the Mongolian Late Cretaceous genera nese (Chui and Li, 1977), assigns this taxon Kennalestes, Asioryctes, and Ukhaatherium, to Zalambdalestidae (Anagalida) because of the last being a new form from Ukhaa Tol- similarities between the upper and lower mo- god. Novacek et al. (1997) noted that the lars of Anchilestes and Kennalestes, accord- presence of epipubic bones and other primi- ing to Ting and Zheng (1989). The latter au- tive features in Asioryctitheria and Zalamb- thors revisited the af®nities of Anchilestes dalestes suggests a basal position in Eutheria, 2004 WIBLE ET AL.: ZALAMBDALESTES 17 and Novacek (1997) ®gured Zalambdalestes Simpson (1928a) were not straightforward at an unresolved trichotomy with the crown- and in some aspects remain ambiguous. The group Placentalia and Asioryctes. More re- dentition in the holotype of Zalambdalestes cently, Ji et al. (2002) have completed a phy- lechei (AMNH 21708) was badly damaged logenetic analysis that allies Zalambdalestes (®gs. 12, 32), and identi®cations by Gregory with Asioryctitheria (®g. 50A). and Simpson (1926a) were drawn from a Finally, in a recent book on fossils from composite of the holotype and AMNH China (Guan, 1998: 111), a photograph of a 21704. These authors speculated that the up- skull in ventral view with disarticulated low- per incisor count was three, but only the dis- er jaws is labeled as Zalambdalestes sp. with tal two incisors were visible. Subsequently, no other information provided. According to Simpson (1928a) cast doubt about the pres- Y.-M. Hu (personal commun.), this form is ence of the distalmost incisor, noting that the actually Kennalestes sp. However, Hu also only certain tooth in the premaxilla was the noted that Zalambdalestes sp. has been re- large caniniform incisor. More troubling, covered from the Bayan Mandahu region of however, was the uncertainty of Gregory and Inner Mongolia, a Djadokhta Formation Simpson (1926a) whether the ®rst tooth in equivalent (Jerzykiewicz et al., 1993). the maxilla was a canine or premolar (see ®g. 32). Situated in the middle of a long diaste- COMPARATIVE MORPHOLOGY ma, well posterior to the premaxillary-maxillary suture, this trenchant, double-rooted DENTITION tooth ``corresponds closely to P2 of recent The dentition of Zalambdalestes has been zalambdodonts but occludes anterior to the described by Gregory and Simpson (1926a), apparent second lower premolar'' (ibid.: 16). Simpson (1928a), and Kielan-Jaworowska Behind this were ®ve postcanine teeth, P3± (1969a, 1984a), and that of Barunlestes by 4, M1±3. Instead of ®ve, six postcanine teeth Kielan-Jaworowska (1975a, 1984a) and Kie- (P2±4, M1±3) were reported by Simpson lan-Jaworowska and Tro®mov (1980). A (1928a) in AMNH 21709, the specimen orig- summary dental characterization for Zalamb- inally identi®ed as the holotype of Z. gran- dalestidae taken from Kielan-Jaworowska geri (synonymized with Z. lechei by Szalay (1984a: 108±109) is as follows: ``Dental for- and McKenna, 1971). In addition, Simpson mula: I3/3, C1/1, P3±4/3±4, M3/3; I2 en- (1928a) reevaluated the premolar count in larged, caniniform, I3 small. Long diastema AMNH 21708 and 21704 and reported P2± between I3 and C. Upper canine very large, 4 for them as well (see ®g. 32). He proposed placed behind premaxillary-maxillary suture, that the ®rst tooth in the maxilla in Zalamb- P1 small or absent, P2 small, P3 tallest of all dalestes must be either the canine or the P1. the teeth, with a spur-like protocone, P4 with He (ibid.: 4) ultimately considered it more protocone developed as in molars, but with- likely to be the canine, even though ``for a out metacone. Upper molars without cingula, canine, it is aberrant, although not altogether strongly elongated transversely, M3 small, i1 unique, in its position far back of the max- enlarged, procumbent, i2, i3, and c small, illo-premaxillary suture.'' styliform, p1 trenchant, p2 trenchant or ab- Kielan-Jaworowska (1969a) reported the sent, p3 with unbasined heel, p4 with three incisor count as ?2 for Zalambdalestes based cusped trigonid and unbasined talonid. [Low- on ZPAL MgM-I/16, which had a small dis- er] Molars with small trigonids, paraconid tal incisor separated by a short diastema from and metaconid connate at bases.'' a large caniniform incisor. A more mesial in- Although the above characterization of the cisor was unknown. Subsequently, without zalambdalestid dental formulae has not been reference to additional evidence, the incisor contested, nor updated with the new infor- count was reported as ?3 by Kielan-Jawo- mation from the recently described zalamb- rowska et al. (1979) and as 3 by Kielan-Ja- dalestid Kulbeckia (Archibald et al., 2001; worowska (1984a), to include a hypothetical Archibald and Averianov, 2003), note that mesial tooth (®g. 4D). The ®rst tooth in the the original identi®cations of dental homol- maxilla was identi®ed as a canine by Kielan- ogies by Gregory and Simpson (1926a) and Jaworowska (1969a), without any reference 18 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 to the uncertainty expressed by Gregory and alveolus has not been reported to date for any Simpson (1926a) and Simpson (1928a). Sub- Zalambdalestes (Gregory and Simpson, sequent authors (e.g., Szalay and McKenna, 1926a; Simpson, 1928a; Kielan-Jaworowska, 1971; Clemens and Lillegraven, 1986; Then- 1969a, 1984a; Kielan-Jaworowska et al., ius, 1989) have followed the identi®cation by 1979). Although the tip of the rostrum is not Kielan-Jaworowska. Instead of the six post- complete in any MAE specimens, Z. lechei canine teeth reported for Zalambdalestes by (PSS-MAE 108 and 130) and cf. Zalamb- Simpson (1928a), seven (P1±4, M1±3) were dalestes sp. (PSS-MAE 131) preserve preserved in ZPAL MgM-I/14 and 16 (Kie- enough of the anteromedial portion of the left lan-Jaworowska, 1969a) (see ®g. 4D). Sub- premaxilla to exclude the presence of the hy- sequently, Szalay and McKenna (1971: 307) pothetical ®rst incisor of Kielan-Jaworowska noted that AMNH 21708 was a very old in- (®gs. 7, 8A, 11). Consequently, the dental dividual and that the ``P1 and P2 have formula of Zalambdalestes requires amend- dropped out and the alveoli have closed.'' ment to two upper incisors in the premaxilla, After reviewing AMNH 21708, we con®rm which we identify here as I1 and 2, merely the presence of an alveolus for the double- re¯ecting the number present. Only one Za- rooted P2 (see also Simpson, 1928a), but lambdalestes specimen has been reported there is no indication whatsoever of an al- previously preserving both the I1 and I2, the veolus immediately in front of the P2 (®g. left side of ZPAL MgM-I/16 (Kielan-Jawo- 32). rowska, 1969a, 1984a). To this, we add both Ambiguity also exists in the lower denti- sides of PSS-MAE 108 (®gs. 11, 23) and the tion of Zalambdalestes regarding the number left side of PSS-MAE 131. The I1 is an en- of premolars. Gregory and Simpson (1926a) larged tooth directed downward and some- originally reported three (p2±4) based on what compressed transversely. The consid- AMNH 21704, but Kielan-Jaworowska erably smaller I2 is situated posterior to and (1969a) found four (p1±4) in ZPAL MgM-I/ separated from the I1 by a short diastema, 4 and 14 (see ®g. 4B). Without any expla- approximately halfway between the I1 and nation of or reference to the condition in the premaxillary-maxillary suture. The I2 is AMNH 21704, four has become the accepted also mildly compressed transversely, more so lower premolar count for Zalambdalestes than the I1, and both its crown and root (vis- (e.g., Kielan-Jaworowska et al., 1979, 2000; ible on the left side of PSS-MAE 108) are Clemens and Lillegraven, 1986; Thenius, slanted posteriorly. A similar degree of pos- 1989). terior slanting for the I2 crown is visible in Below we reevaluate the dental formula AMNH 21704 and in ZPAL MgM-I/16 and tooth homologies of Zalambdalestes in (based on Kielan-Jaworowska, 1984a: pl. light of the evidence provided by the MAE 16). None of these specimens preserves specimens. We have included pencil draw- enough detail to ascertain whether the upper ings and stereophotographs of the anterior incisors had restricted enamel, as we report and posterior upper dentition of PSS-MAE below for the enlarged i1. The left side of 130 (®gs. 7±10), the only MAE specimen PSS-MAE 130 has two alveoli for the pre- that provides new detail on crown morphol- maxillary incisors (®gs. 7, 8A). ogy. Dental measurements are listed in table One of the MAE Zalambdalestes has what 2, and illustrations of our dental terminology we interpret to be an additional incisor (I3) and measurements are in ®gures 5 and 6. wholly or largely in the maxilla. On the left UPPER INCISORS: In her synopsis of the za- side of PSS-MAE 130 (®gs. 7, 8A) a small lambdalestid skull, Kielan-Jaworowska alveolus in the maxilla is separated by a di- (1984a) reported three upper incisors in the astema from the front of the large, trenchant, dental formula. Given that only the alveolus double-rooted tooth identi®ed as a canine by is known for one upper incisor in Barunlestes most authors (e.g., Simpson, 1928a; Kielan- (Kielan-Jaworowska and Tro®mov, 1980), Jaworowska, 1969a, 1984a), including us the identi®cation of three incisors necessarily (see below). The shape and orientation of the was based on Zalambdalestes (®g. 4B, D). alveolus suggest that its occupant was slant- Nevertheless, the purported ®rst incisor or its ed posteriorly and not vertically inset. On the 2004 WIBLE ET AL.: ZALAMBDALESTES 19

TABLE 2 Upper Dentition Measurements (mm) of Zalambdalestes 20 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 5. M2 amd m3 of Zalambdalestes lechei ZPAL MgM-I/43 (modi®ed from Crompton and Kie- lan-Jaworowska, 1978: ®g. 9), illustrating the dental terminology employed here. Abbreviations: cec, centrocrista; co, cristid obliqua; e¯, ecto¯exus; end, entoconid; hyd, hypoconid; hyld, hypoconulid; med, metaconid; met, metacone; metl, metaconule; pad, paraconid; par, paracone; parl, paraconule; pas, parastyle (stylar cusp A); pmc, postmetacrista; pomlc, postmetaconular crista; popc, postprotocrista; poplc, postparaconular crista; prd, protoconid; prmlc, premetaconular crista; pro, protocone; prpc, preprotocrista; prplc, preparaconular crista; st, stylocone (stylar cusp B); tal, talonid; tb, trigon basin; trd, trigonid. specimen's right side (®gs. 7, 8A, 29), a found in the zalambdalestid Kulbeckia kul- small, single-rooted, styliform tooth is pre- becke, which preserves the roots of three up- served in front of the canine. As predicted per incisors (®g. 52): the ®rst is entirely with- from the alveolus on the left side, this tooth in the premaxilla, the second between the is slanted posteriorly, but to a greater degree premaxilla and maxilla, and the third entirely than in the life position; its tip has been dis- within the maxilla (Archibald and Averianov, placed such that it nearly touches the base of 2003). The Mongolian Late Cretaceous the canine. This peglike tooth is within the asioryctitheres also have incisors in the premaxilla. Although we deem it unlikely, the maxillary-maxillary suture; Ukhaatherium premaxilla may have contributed to the al- nessovi has the last incisor (I5) in the max- veolus anteriorly. Based on a facet on the illa, with the premaxilla contributing to the anterolateral surface of the maxilla, the pos- anterior quarter of the alveolar border (No- terolateral part of the palatal process of the vacek et al., 1997; personal obs.), and Asio- premaxilla, which is not preserved on either ryctes nemegtensis and Kennalestes gobien- side, may have sent a narrow, triangular sis have the last incisor (I5 and I4, respec- wedge posteriorly that approximated or con- tively) in the premaxillary-maxillary suture tributed anteriorly to the alveolus. (®g. 51D, E; Kielan-Jaworowska, 1981). In- The small tooth in PSS-MAE 130 could cisors at least partly within the maxilla may be interpreted as an incisor or as an aberrant, be primitive for Eutheria, although the mor- reduced, deciduous or adult canine. Of these phology in question is not known for most possibilities, we think that it most likely is of the relevant outgroups. In the basal mam- an incisor wholly or nearly completely with- maliaform Morganucodon oehleri, the I4 is in the maxilla. A similar arrangement is in the maxilla (Kermack et al., 1981), and in 2004 WIBLE ET AL.: ZALAMBDALESTES 21

ditional maxillary tooth in front of the canine on one side only. On the right side of cf. Zalambdalestes sp. PSS-MAE 131 is a tooth in front of the canine essentially identical to it in size and morphology, although we cannot evaluate the number of roots on either tooth, as the right side of the specimen is still in the matrix block. As reconstructed from the right premaxilla, which is detached from the skull, this extra tooth is entirely within the maxilla, far from the suture with the premaxilla. Because this extra caniniform is clearly not present on the left side of the specimen, we treat its appearance on the right as an anomaly. Of the last remaining MAE specimen preserving the rostrum, PSS-MAE 129, the occurrence of an extra tooth or alveolus in front of the canine cannot be determined due to damage (®g. 31). The con- Fig. 6. M2 of Zalambdalestes lechei ZPAL dition in PSS-MAE 131 may re¯ect a taxo- MgM-I/43 (modi®ed from Crompton and Kielan- nomic difference with previously known Za- Jaworowska, 1978: ®g. 9), illustrating the dental lambdalestes, but given that the study of this measurements in table 2. Abbreviations: A, dis- specimen is still in progress, we postpone tance between lingualmost point of protocone base to its apex; B, distance between protocone further consideration of this problem. and paraconule; C, distance between paraconule After discovering these additional teeth in and paracone; D, distance between paracone and the maxilla in front of the canine, we reex- labialmost point of crown; L, greatest anteropos- amined the AMNH Zalambdalestes and the terior length; W-A, greatest labiolingual width stereophotographs of the ZPAL and PIN from anterolabial corner to lingualmost point of specimens in Kielan-Jaworowska (1969a, protocone base; W-P, greatest labiolingual width 1984a). The only one that may have borne a from posterolabial corner to lingualmost point of maxillary incisor is AMNH 21709, in which protocone base. there is a narrow gap in the alveolar margin anterior to the right canine in the same place as the alveolus for the maxillary incisor in the docodontid Haldanodon exspectatus the PSS-MAE 130. The only specimens clearly I5 is in the premaxillary-maxillary suture and showing that an alveolus in the maxilla in the I6 in the maxilla (Lillegraven and Krusat, front of the canine is lacking are AMNH 1991). In a more proximate outgroup, Dry- 21708 (®g. 32) and perhaps ZPAL MgM-I/ olestoidea, the I4 is in the maxilla in an un- 13 (see Kielan-Jaworowska, 1984a: plate described new genus of paurodontid from the 17). Morrison Formation of Fruita, Colorado UPPER CANINE: Gregory and Simpson (Hopson et al., 1999; personal obs.). (1926a) identi®ed the ®rst tooth in the max- A second MAE specimen preserves an ad- illa in AMNH 21708 (®g. 32) and 21704, ditional alveolus in front of the canine on one which is double-rooted, trenchant, and iso- side only. The right side of PSS-MAE 108 lated by diastemata, as either a canine or pre- has a small alveolus entirely within the max- molar. Simpson (1928a) also questioned the illa comparable in size to that for the max- identi®cation of this tooth referring to illary incisor in PSS-MAE 130. It is, how- AMNH 21709, but considered the canine to ever, situated slightly nearer the canine than be the more likely interpretation despite its is the maxillary incisor in PSS-MAE 130. position well posterior to the premaxillary- The left side of PSS-MAE 108 has no alve- maxillary suture. We follow all subsequent olus corresponding to that on the right. authors on the subject (e.g., Kielan-Jawo- A third MAE specimen preserves an ad- rowska, 1969a, 1984a; Szalay and McKenna, 22 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 7. The rostrum of Zalambdalestes lechei PSS-MAE 130 in ventral view. Pattern represents matrix. Abbreviations: art, artifactual opening; C, upper canine; cr, crest; I1a, upper ®rst incisor alveolus; I2a, upper second incisor alveolus; I3, upper third incisor; I3a, upper third incisor alveolus; inf, incisive foramen; mx, maxilla; pmx, premaxilla; rp, rostral process of premaxilla.

1971) in identifying the double-rooted, tren- 21708 (®g. 32), and 21709. In contrast, Kie- chant tooth in the maxilla as the canine. This lan-Jaworowska (1969a) reported four pre- identi®cation is supported by the close po- molars (P1±4) in ZPAL MgM-I/14 and 16 sitional relationship of this tooth with the (®g. 4B, D). Her descriptions (ibid.: 186± maxillary incisor in PSS-MAE 130. Among 188) are repeated here with differences in the the MAE specimens, the canine is preserved MAE specimens noted. on both sides of PSS-MAE 108 (®gs. 11, 23, ``P1 small, two-rooted, slightly com- 25), 130 (®gs. 26, 29), and 131, and on the pressed, asymmetrical, with a single cusp sit- right side of PSS-MAE 129 (®g. 31). uated in the prolongation of anterior root. No UPPER PREMOLARS: Following Simpson cingulum. In lateral view, the tooth (exclud- (1928a), there are three premolars (P2±4) ing roots), has the appearance of a scalene just rostral to the molars in AMNH 21704, triangle, with anterior crest directed down- 2004 WIBLE ET AL.: ZALAMBDALESTES 23 wards, posterior crest longer, directed diag- In front of these minute styles, the outer part onally. A very short diastema between P1 of the tooth is smooth; in the most anterior and P2'' (Kielan-Jaworowska, 1969a: 186). part a parastyle is present. The spur-like pro- The P1 preserved on the left side of PSS- tocone is asymmetrical, directed obliquely MAE 108 conforms to this pattern (®gs. 11, antero-medially, much lower than the para- 23); the crown is missing from the right P1. cone'' (Kielan-Jawrowska, 1969a: 186±188). The P1 is also preserved on the right side of The P3 preserved on the left side of PSS- PSS-MAE 129, but is severely worn (®g. MAE 108 (®gs. 11, 23) and on the right side 31). As in AMNH 21704, 21708 (®g. 32), of PSS-MAE 129 (®g. 31) are heavily worn and 21709, the P1 is wholly lacking in PSS- and only visible in lateral view. In PSS-MAE MAE 130 (®g. 8). This is also true for Ba- 130 (®gs. 8, 9), the right and left P3 are well runlestes (®g. 51B; ZPAL MgM-I/77, Kie- preserved, with only slight wear to the crest lan-Jaworowska, 1975a; ZPAL MgM-I/104, running from the paracone to the metastylar PIN 3142±701, Kielan-Jaworowska and Tro- area, and by and large conform to the above ®mov, 1980). pattern. One difference concerns the crest be- P2 ``is somewhat larger than P1, two-root- tween the paracone and metastyle. Although ed, compressed laterally, with a prominent only one cuspule in this crest (the incipient main cusp and a minute anterior basal cusp. metacone) is mentioned in the description by A lingual cingulum extends from the anterior Kielan-Jaworowska, two cuspules of unequal cusp to a point opposite the middle of the size are shown in her reconstructions (1969a: main cusp, and is absent from the posterior ®g. 4A, B). The crest between the paracone half of the tooth'' (Kielan-Jaworowska, and metastyle in PSS-MAE 130 has a distinct 1969a: 186). The P2 is preserved in PSS- incipient metacone and two small, more la- MAE 108 (®gs. 11, 23), 129 (®g. 31), and bial cuspules (®g. 9): the lower one in the 130 (®gs. 8, 9), but it is only in the last that metastylar position (stylar cusp E) and the the morphology of this tooth can be checked. other in the intersection of the postmetacrista As preserved on both sides, the P2 conforms and postprotocrista. The two minute styles to the pattern described by Kielan-Jawo- anterior to stylar cusp E described by Kielan- rowska (1969a) with one exception: the lin- Jaworwoska (1969a) are more pronounced in gual cingulum is not present in the anterior PSS-MAE 130, in particular the more ante- part of the tooth but near the midpoint, just rior one, which is situated immediately pos- posterior to the level of the main cusp. As terior to the ecto¯exus. The parastyle (stylar apparent on the left side of PSS-MAE 108 cusp A) is also more pronounced in PSS- (®gs. 11, 23), the P2 is somewhat larger (lon- MAE 130, and posterior to it is a very weak ger and wider) than the P1, also noted by style (stylar cusp B). Finally, there is a low, Kielan-Jaworowska (1969a). However, the but distinct paraconule in PSS-MAE 130, P1 projects farther ventrally than the P2 (®g. particularly on the left side, without wings. 11); the reconstruction by Kielan-Jaworow- Most of these differences are probably the ska (1969a: ®g. 4B) shows the reverse (®g. result of additional wear on the ZPAL spec- 4B). imens. ``P3 is subtriangular in occlusal view, with ``P4 is similar in structure to P3, but has a large main cusp (paracone) situated close a protocone developed as in true molars. In to the external border and a spur-like proto- lateral view, it is smaller than P3. On the cone. On the posterior crest of the paracone posterior crest of paracone V, there is a small V (in lateral view), there is a very small cus- cuspule identi®ed as an incipient metacone, pule, which is identi®ed here as an incipient similar to that in P3, a prominent metastyle metacone. At the posterior end of this crest, being situated in its posterior prolongation. in the prolongation of the paracone and meta- The stylar shelf is developed although nar- cone cusps, there is a large, prominent met- rower in the middle than in the molars. In astyle. The stylar shelf is not actually devel- addition to the prominent parastyle and me- oped, however, one can recognize in the pos- tastyle, there are three hardly discernible, mi- terior part of the tooth, in addition to the me- nute styles, two posterior ones situated close tastyle, two minute styles hardly discernible. to the metastyle, anteriorÐclose to the par- 24 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 8. Stereophotographs of the upper dentition of Zalambdalestes lechei PSS-MAE 130 in ventral (A) and left lateral (B) views. astyle. The protocone is situated lower than the description of Kielan-Jaworowska the paracone, directed transversely, with a (1969a). However, as reported above for the slight anterior deviation. The precingulum P3, the crest connecting the paracone and and postcingulum are lacking. The surface metastyle in PSS-MAE 130 has an incipient between the protocone and paracone [trigon metacone and two cuspules in the metastylar basin] is hollowed out by wear, retaining a region (®g. 10A, C): in the E position (i.e., very characteristic transverse ridge in the the metastyle) and lingual to it. The three middle, absent from other teeth'' (Kielan-Ja- styles between the parastyle and metastyle worowska, 1969a: 188). As was true of the that Kielan-Jaworowska (1969a) described as P3, the P4s in PSS-MAE 108 (®gs. 11, 23) ``hardly discernible'' are slightly more pro- and 129 (®g. 31) are heavily worn and pronounced in PSS-MAE 130 (®g. 10A, C). The vide few morphological details. In PSS-MAE anterior one (stylar cusp B) is separated from 130 (®gs. 8, 9, 10A, C), both right and left the parastyle by a notch; the posterior two P4 are well preserved, with only slight wear are immediately posterior to the ecto¯exus. to the crest between the paracone and incip- Of these three, the middle (stylar cusp D?) is ient metacone, and in most regards follow the most distinct, although not as prominent 2004 WIBLE ET AL.: ZALAMBDALESTES 25

Fig. 8. Continued. as the parastyle. Finally, on the pre- and post- during mastication. The best preserved, least protocristae are a low paraconule, with pre- worn molar series belong to ZPAL MgM-I/ and postparaconule cristae, and a worn meta- 14, 16, and 43 (Crompton and Kielan-Ja- conule without wings (®g. 10A, C). Presum- worowska, 1978: ®gs. 9, 11; Kielan-Jawo- ably additional wear to these structures pro- rowska, 1984a: pl. 14); the M2 from the last duced the transverse ridge in the trigon ob- is shown diagrammatically in ®gure 5. The served by Kielan-Jaworowska (1969a). descriptions by Kielan-Jaworowska (1969a: UPPER MOLARS: The molars in the CAE 188±189) based on ZPAL MgM-I/14 and 16 specimens described by Gregory and Simp- are repeated here, with differences noted for son (1926a) and Simpson (1928a) are heavily PSS-MAE 130, the only MAE specimen worn and provide only general clues to their with well-preserved molars (®gs. 8, 9). morphology. In contrast, the ZPAL speci- ``M1 and M2 are similarly developed and mens show morphological detail (Kielan-Ja- are described here together, M1 being some- worowska, 1969a) from which Crompton what wider transversely than M2 . . . The and Kielan-Jaworowska (1978) were able to paracone and metacone are situated strongly reconstruct the pattern of molar occlusion labially, the paracone higher than the meta- 26 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 9. The left P2±M3 of Zalambdalestes lechei PSS-MAE 130 in labial and occlusal views. cone. The parastyle and metastyle are prom- ci®cally, a stylocone (stylar cusp B) is ®g- inent, the stylar shelf well developed (partic- ured, as are winged paraconule and metaco- ularly at the ends). On the stylar shelf, in nule approximating the paracone and meta- addition to the parastyle and metastyle, there cone (see also Butler, 1990). Clemens and are two or three minute accessory styles, Lillegraven (1986) described the conules in hardly discernible, the mesostyle not being Zalambdalestes as weak. In PSS-MAE 130 developed. The protocone is situated lower (®gs. 9, 10B, D), a weak stylocone (stylar than the paracone and metacone. Incipient cusp B) is present on the M1 but is imper- conules are very indistinct. Precingulum and ceptible on the stylar shelf of M2. Also, in postcingulum are lacking. The surface be- the metastylar region of the M2, the stylar tween the protocone and paracone-metacone shelf is reduced, with no cusps and almost W is strongly concave, hollowed out by no ridge. Wear to the M1 and M2 has eroded wear'' (Kielan-Jaworowska, 1969a: 188± the conules. As noted by Kielan-Jaworowska 189). Additional details based on ZPAL (1969a), the paracone is higher than the MgM-I/43 (®g. 5) are shown in the diagrams metacone, but the size disparity is slight. As of M2 in Crompton and Kielan-Jaworowska preserved, the protocone is somewhat lower (1978: ®g. 9) and in the stereophotographs than the paracone and metacone, but this also in Kielan-Jaworowska (1984a: pl. 14). Spe- may be the result of wear. Additional features 2004 WIBLE ET AL.: ZALAMBDALESTES 27

Fig. 10. The left P4 and M1 of Zalambdalestes lechei PSS-MAE 130 in labial (A, B) and occlusal (C, D) views. Abbreviations: D, stylar cusp D; e¯, ecto¯exus; mes, mesostyle (stylar cusp E); met, metacone; metl, metaconule; par, paracone; parl, paraconule; pas, parastyle (stylar cusp A); pmcc, postmetacrista cusp; popc, postprotocrista; pro, protocone; prpc, preprotocrista; st, stylocone (stylar cusp B). 28 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 coded by Rougier et al. (1998) include para- numeration for Zalambdalestes. We follow cone and metacone bases that are separate; a all previous authors (e.g., Gregory and Simp- preprotocrista that does not extend labially son, 1926a; Kielan-Jaworowska, 1969a, beyond the base of the paracone; a postpro- 1984a) in identifying the three incisors in Za- tocrista that does extend labially beyond the lambdalestes as i1±3, but note the possibility base of the metacone; a centrocrista between that our i2 and 3 might be equivalent to the the paracone and metacone that is V-shaped i3 and 4 of Kulbeckia. (though not to the same extent as in some One of the most distinctive features of the metatherians); and an ecto¯exus that is very dentition of Zalambdalestes is the enlarged, shallow, although deeper on the M1 than M2. procumbent, anterior lower incisor, which we ``M3 is a small tooth. The metacone is dis- label as i1. It was described ®rst by Gregory tinctly lower than the paracone. The paras- and Simpson (1926a) based chie¯y on tyle is distinct, the stylar shelf is present only AMNH 21704, which preserves the bulk of in the anterior half of the tooth, while the the tooth, minus the tip. However, because of metastyle is lacking. The protocone is situ- poor specimen preservation, the description ated lower than the paracone-metacone. On by Gregory and Simpson (1926a: 17) was the postprotocrista, near the metacone base, very limited: ``much enlarged, procumbent, is a curvature outwards. The surface of the and occludes between the enlarged upper in- crown is hollowed out by wear, the conules cisors'' [the I1 of our report]. The three low- not discernible'' (Kielan-Jaworowska, er jaws described by Kielan-Jaworowska 1969a: 189). The M3 in PSS-MAE 130 has (1969a: ZPAL MgM-I/4 and 14) and Kielan- distinct winged conules, with the metaconule Jaworowska and Tro®mov (1981: PIN 3143± clearly better developed than the paraconule, 501) did not provide additional details, as possibly an artifact of wear (®gs. 8A, 9). In only the i1 alveolus and/or root were pre- fact, the ``curvature outwards'' observed by served. Two specimens (ZPAL MgM-I/43 Kielan-Jaworowska (1969a) is the postmet- and 77) preserving part of the i1 crown have aconule crista. The conules are proportion- been ®gured by Kielan-Jaworowska et al. ally closer to the paracone and metacone than (1979: ®g. 12±2A) and Kielan-Jaworowska in the M1 and M2 (see Crompton and Kie- (1984a: pl. 14, 15, 17), but not described. lan-Jaworowska, 1978: ®g. 9), which may be Recently, Fostowicz-Frelik and Kielan-Ja- a consequence of the smaller crown size of worowska (2002) have published more de- the M3. tails from two specimens of Z. lechei,ZPAL LOWER INCISORS AND CANINE: Zalambda- MgM-I/43 and 51. In both, damage to the lestes preserves three lower incisors, which inferior border of the mandible revealed that Gregory and Simpson (1926a) and Kielan- the root of the lower incisor was present, and Jaworowska (1969a, 1984a; Kielan-Jawo- open below the p4 and anterior part of m1. rowska and Tro®mov, 1981) designated as i1, Two of the MAE specimens are the ®rst i2, and i3. If the primitive eutherian condi- Zalambdalestes to preserve essentially the tion is four lower incisors (Rougier et al., entire i1. In Z. lechei PSS-MAE 108, in 1998; Ji et al., 2002), it is uncertain which which the jaws are in articulation, the left i1 tooth positions are represented by the three is nearly complete (®gs. 11, 23). The tip lower incisors in Zalambdalestes. Behind its shows some breakage and most of the enam- enlarged, procumbent, anterior incisor, Kul- el is missing (eroded). The tooth is 7.0 mm beckia has three single-rooted alveoli (®g. in length from alveolus to tip and extends 51C), which Archibald and Averianov almost to the rostral tip of the premaxilla, (2003) identify as i2±4. These authors noted passing just medial to the I1. Details of the that the position of the i3 and i4 in Kulbeckia crown morphology are obscured by matrix resembles the i2 and i3 in Zalambdalestes left in place to buttress the tooth. The right and, therefore, suggested that Zalambdales- i1 is broken off at the alveolus, revealing an tes does not preserve or has lost the i2. Be- oval root. Additionally, bone is missing cause these authors expressed some uncer- along the inferior margin of the right man- tainty about the existence of the i2 alveolus dible, revealing that the root extends poste- in Kulbeckia, we choose not to follow their riorly at least below the front edge of the p4. 2004 WIBLE ET AL.: ZALAMBDALESTES 29

Fig. 11. Stereophotographs of the anterior part of the skull and lower jaws of Zalambdalestes lechei PSS-MAE 108 in ventral (A) and lateral (B) views. 30 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

In cf. Zalambdalestes sp. PSS-MAE 131, in have modi®ed our view regarding the ab- which the jaws are in articulation but the presence of enamel based on cf. Zalambdalestes maxillae are displaced, both the right and left sp. PSS-MAE 145, in which the root of the i1 are retained (see Novacek et al., 1997: ®g. left i1 is exposed posteriorly to the level of 3). The teeth are oval in cross section near the canine and reveals enamel continuous the alveolus but subtriangular approaching from the crown to the root. In Kulbeckia, the tip, which shows little or no wear. Ad- enamel on the i1 is reported to extend to at ditionally, the teeth have enamel restricted, least within 1 mm of the apical root opening in cross section, to the buccal half from the (Archibald and Averianov, 2003). alveolus to the tip. The left i1 preserved in Behind the enlongated i1 in Zalambdales- cf. Zalambdalestes sp. PSS-MAE 145 con- tes (AMNH 21704), Gregory and Simpson forms to the same pattern, except that the tip (1926a) found three small, styliform, single- is missing. Incisors with restricted enamel rooted teeth that exhibit decreasing procum- occur in a variety of extinct and extant mam- bency posteriorly. The identi®cation by mals, including various multituberculates Gregory and Simpson of the ®rst two teeth (Simmons, 1993), rodents, and lagomorphs as the i2±3 and the third as the lower canine (Koenigswald, 1985, 1988; Thenius, 1989). has been accepted by all subsequent authors The enlongated, procumbent i1 is damaged (except Archibald and Averianov, 2003; see in all specimens of Barunlestes (®g. 51B; above). Con®rming the incidence of three Kielan-Jaworowska, 1975a; Fostowicz-Frelik styliform teeth behind the i1 are four Za- and Kielan-Jaworowska, 2002), and its root lambdalestes specimens housed in Warsaw is open and reaches posteriorly under the (®g. 4B; ZPAL MgM-I/4, 13, 43, and 51: posterior part of m1 (Fostowicz-Frelik and Kielan-Jaworowska, 1969a, 1984a) and one Kielan-Jaworowska, 2002). As in PSS-MAE in Moscow (PIN 3143±501: Kielan-Jawo- 131, according to McKenna (1994: 57), the rowska and Tro®mov, 1981). The only Ba- i1 of Barunlestes has ``enamel restricted to runlestes specimen preserving the anterior an outer U-shaped band.'' It is unclear what lower dentition is said to exhibit the same specimen of Barunlestes McKenna used for pattern (®g. 51B; ZPAL MgM-I/77: Kielan- his observation, and it may even be that of Jaworowska, 1975a). Kulbeckia differs in a new genus, related to eurymylids (Fostow- that it likely had four lower incisors and its icz-Frelik and Kielan-Jaworowska, 2002). In lower canine is either two-rooted or with a Kulbeckia, the open root of the enlongated, single bifurcated root (®g. 51C; Archibald procumbent i1 extends below p2, and the and Averianov, 2003). enamel of this tooth is thickened on all but Two of the MAE Zalambdalestes preserve the dorsolingual surface, where the enamel is details of the anterior lower dentition. On the either very thin or absent (Archibald et al., right side of PSS-MAE 108, the i2±3 and c 2001; Archibald and Averianov, 2003). are broken near their alveoli, with the broken These authors noted that the incidence of an bases showing an increase in size posteriorly. apical root opening may re¯ect the young The i2±3 are subcircular at their bases, age of the specimen or may indicate that the whereas the canine is more ovoid. On the left tooth was gliriform or ever-growing. side of the specimen (®gs. 11, 23), the i2 and In Zalambdalestes PSS-MAE 129 (®g. c are preserved. The former is procumbent 39), the exposed root of the i1 was investi- and ®ngerlike with a slight increase in di- gated by Thomas Martin (Freie UniversitaÈt, ameter toward the tip; the latter is semipro- Berlin) in hopes of obtaining a sample of cumbent and widest at its ovoid base, taper- enamel for analysis with scanning electron ing toward the tip. Separating the i2 and c is microscopy. He reported that enamel was a wide gap, which contains the alveolus for lacking from the root, suggesting that the in- the i3. On the left side of PSS-MAE 129, the cisor is not ever-growing or gliriform, a con- broken root of the i1 and c and the alveoli dition that does occur in rodents, lago- of the i2±3 conform to the pattern described morphs, vombatid marsupials, and the pri- above for PSS-MAE 108. mate Daubentonia among others (Koenig- In PSS-MAE 108, the upper and lower swald, 1985). Subsequently, however, we jaws are articulated in a fashion that re¯ects 2004 WIBLE ET AL.: ZALAMBDALESTES 31 an occlusive position that was possible dur- . . . p1 is trenchant, very slightly procum- ing life (®gs. 11, 23). The anterolabial tip of bent, with a prominent main cusp and a mi- the enlarged i1 is in close proximity to the nute accessory cusp situated posteriorly. p2 lingual surface of the I1, and these teeth like- is situated after a very short diastema behind ly contacted one another (®gs. 11, 23). It is p1. It is very small, insigni®cantly procum- doubtful that any contact between the i1 and bent, with anterior main cusp and a minute I2 was possible. The i2 and i3 are situated in posterior one. p3 is larger than p1 and p2, the long diastema between the I2 and C and consisting of a main cusp, with a minute ac- may not have contacted any upper teeth be- cessory cusp in front of it, and small, unba- cause that would have required a consider- sined heel with one low cusp (entoconid). able protrusion of the lower jaw. The canines The entoconid is situated lingually, the labial likely contacted one another, with the lower part of the heel sloping steeply downwards. one situated just anterior to the upper (®gs. p4 is submolariform, highest of all the teeth, 11, 23). with three-cusped trigonid and an unbasined LOWER PREMOLARS: In their original de- talonid. The protoconid is highest, somewhat scription and diagnosis of Zalambdalestes connate (in posterior view) at the base with lechei, Gregory and Simpson (1926a) re- the lower metaconid. The paraconid is much ported three lower premolars, p2±4. The p2 lower and smaller than the protoconid and description was taken from AMNH 21704: metaconid, situated at the anterior edge of ``p2 smaller than p3 and more procumbent.'' the tooth. The talonid is much shorter than The description (ibid.: 17) of the p3±4 was that of m1, with a single cusp situated lin- based on AMNH 21707 and 21708 (®gs. 12, gually and the labial part steeply sloping 13): p3 ``trenchant, two-rooted, consisting of downwards.'' In subsequent reports (Kielan- a single cusp with a small unbasined heel''; Jaworowska and Tro®mov, 1981; Kielan-Ja- and p4 ``molariform, similar to m1 but high- worowska, 1984a), four more Zalambdales- er and with a much shorter talonid and rel- tes preserving four lower premolars were il- atively elongated trigonid.'' Although not de- lustrated (ZPAL MgM-I/13, 43, and 51; PIN scribed, the drawings of AMNH 21704 and 3143±501). The only exception is the right 21708 (ibid.: ®gs. 15, 17, 18) show a diaste- side of ZPAL MgM-I/43 in which the p2 is ma between the p2 and p3 (see ®g. 12). Our missing (see above). In addition, Kielan-Ja- reexamination of these specimens in light of worowska and Tro®mov (1981) suggested ZPAL, PIN, and MAE materials reveals that that the p4 in ZPAL MgM-I/14, a very young the tooth originally designated by Gregory individual, is a deciduous tooth, because it and Simpson (1926a) as the p2 is actually has an anterior basal cusp, which is lacking the p1 and that the p2 is missing. Kielan- in all other specimens. Jaworowska (1984a: pl. 15) illustrated a right Two MAE Zalambdalestes provide infor- lower jaw of Z. lechei (ZPAL MgM-I/43) mation regarding the lower premolars. PSS- that apparently exhibits the same pattern (i.e., MAE 108 (®gs. 11B, 23) repeats the pattern a diastema between the p1 and p3, and no of four premolars in the Warsaw and Mos- alveolus for the p2); the left lower jaw of the cow specimens (with the exception of the specimen has the p2 in place. right side of ZPAL MgM-I/43). In PSS-MAE Kielan-Jaworowska (1969a) described the 129 (®g. 31), the right lower jaw has only dentition in three Zalambdalestes specimens three teeth preserved anterior to the m1; the (ZPAL MgM-I/4, 14, and 16), each of which left lower jaw is severely damaged. The pos- had four double-rooted lower premolars (p1± terior two teeth, the p3±4, are separated from 4) (®g. 4B). However, the discrepancy in the the anterior one by a very short gap. We in- premolar count with the specimens described terpret the anterior tooth as the p1; it is too by Gregory and Simpson (1926a) was not large to be the p2, which in all other Za- noted. The descriptions of the premolars by lambdalestes is considerably smaller than the Kielan-Jaworowska (ibid.: 189) are repeated p1. Consequently, PSS-MAE 129 resembles here; the MAE specimens do not reveal any AMNH 21704 and 21708 and the right side additional details about crown morphology: of ZPAL MgM-I/43 in lacking the p2. This ``Between c and p1 there is a short diastema is also true for Barunlestes (®g. 51B; ZPAL 32 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

MgM-I/77, Kielan-Jaworowska, 1975a; are found in ZPAL MgM-I/16 and the left ZPAL MgM-I/90, 107, and 135, PIN 3142± sides of PSS-MAE 108 (®gs. 11, 23) and 701, Kielan-Jaworowska and Tro®mov, 131; three are found in PSS-MAE 130 (®gs. 1980). Kielan-Jaworowska and Tro®mov 7, 8) and the right side of PSS-MAE 108. (1980: 168±169) mistakenly identi®ed alve- Regarding the premolars, four are preserved oli for the p2 in ZPAL MgM-I/90 and 135 in both the upper and lower jaws in ZPAL (Kielan-Jaworowska, personal commun.). MgM-I/13, 14, and 16 and PSS-MAE 108 LOWER MOLARS: The three MAE Zalamb- (®gs. 11B, 23), and three are preserved (P2± dalestes specimens with lower jaws do not 4 and p1, 3±4) in both upper and lower jaws provide details on lower molar crown mor- in AMNH 21704 and 21708 (®gs. 12, 32). phology because the jaws are in occlusion The only specimen with an uneven count in (®gs. 11B, 30, 31). The most detailed de- the upper and lower jaws is PSS-MAE 129, scription of the lower molars of Zalambda- which has P1±4 and p1, 3±4 (®g. 31). We lestes is that of ZPAL MgM-I/14 by Kielan- have no evidence that any of the preserved Jaworowska (1969a: 189), which is repeated teeth in any Zalambdalestes are retained de- here (®g. 5): ``m1 and m2 are similarly ciduous teeth, other than perhaps the p4 in shaped. m2 is lower and smaller than m1. ZPAL MgM-I/14, as suggested by Kielan-Ja- The trigonid in m1 is smaller than in p4, the worowska and Tro®mov (1981). In fact, in talonid larger. The paraconid and metaconid PSS-MAE 130, the P3±4 show considerably are connate at their bases, the former being less wear than the M1±3 (®gs. 8, 9), sug- distinctly smaller and lower than the latter. gesting that they are replacement teeth that The protoconid is somewhat higher than the erupted after the molars. It may be that the metaconid. The talonid is strongly basined, observed variation in upper incisor and upper with poorly de®ned cusps. One can recognize and lower premolar number is representative the higher entoconid and lower hypoconid of different taxa among the current sample. which slightly projects laterally. (A low hy- Other than tooth number, there are few dental poconulid was reconstructed on the m2 by and cranial differences that can be used to Crompton and Kielan-Jaworowska [1978] distinguish the available sample, especially based on ZPAL MgM-I/43.) m3 is the small- when one accounts for differing states of est of the molars, narrower and shorter than preservation and tooth wear. Before taxo- m2, with very small trigonid. The paraconid nomic revision can be addressed, the ZPAL is vestigial, strongly connate with the meta- and PIN specimens must be reevaluated in conid, the protoconid is lower than the meta- light of all the MAE material, which we have conid. The talonid is comparatively large, not yet done. strongly basined, with three cusps. The en- The dental formula reported for Barunles- toconid is the highest, the hypoconulid situ- tes butleri by Kielan-Jaworowska (1975a) is ated close to it and insigni®cantly lower, the I?/i3, C1/c1, P3/p3, M3/m3 (®g. 51B). We hypoconid the lowest.'' Based on Crompton identify the lower incisors in Barunlestes as and Kielan-Jaworowska (1978: ®g. 10), we i1±3, but note the possibility raised by Ar- add here that the talonid is wider and longer chibald and Averianov (2003) for Zalamb- than the trigonid on m1±3. The paraconid is dalestes that the distal two incisors in Ba- lingually positioned, in alignment with the runlestes may be homologous with the i3 and metaconid. The metacristid is transversely i4 of Kulbeckia. Our dental formula for Za- oriented, and the cristid obliqua is labially lambdalestes affects the diagnosis of Barun- placed, at the base of the protoconid. The lestes, which preserves three upper premo- hypoconulid is in a posteromedial position, lars, identi®ed as P2±4, and three lower pre- slightly nearer the entoconid than hypoconid. molars, identi®ed as p1, 3±4. The absence of DENTAL FORMULA: As already noted, a va- the P1 and p2 was noted amongst the fea- riety of dental formulae have been reported tures distinguishing Barunlestes and Zalamb- for Zalambdalestes lechei. In our reconsid- dalestes by Kielan-Jaworowska (1975a; see eration of this topic, we have found the fol- also Kielan-Jaworowska et al., 1979, 2000; lowing formulae: I2±3/i3, C1/c1, P3±4/p3± Kielan-Jaworowska and Tro®mov, 1980). 4, M3/m3. Regarding the upper incisors, two However, the utility of these as diagnostic 2004 WIBLE ET AL.: ZALAMBDALESTES 33

Fig. 12. Stereophotographs of the lower jaws of Zalambdalestes lechei AMNH 21708 in occlusal view. features of Barunlestes is questioned by our Zalambdalestes is three. We question the report above of the absence of these teeth in number of upper incisors in Kulbeckia. The some specimens of Zalambdalestes. one specimen preserving evidence for the The dental formula reported by Archibald upper incisors, URBAC 99±53, has only et al. (2001) for Kulbeckia kulbecke (I3, 4, three alveoli (®g. 52), but Archibald et al. or 5/i4, C1/c1, P4/p4, M3/m3) (®gs. 51C, 52) (2001) and Archibald and Averianov (2003) differs from that in Zalambdalestes with re- speculated that as many as ®ve incisors gard to the incisor and premolar count. There might have been present. We see no basis for are four premolars in both the upper and low- any speculation beyond the evidence of the er jaws in all relevant preserved specimens three upper incisor alveoli, which resembles of Kulbeckia, as occurs in some Zalambda- some Zalambdalestes. lestes. Archibald and Averianov (2003) identi®ed these as P1, 2, 4, 5 and p1, 2, 4, 5, LOWER JAW based on the interpretation that position 3 is lost in early eutherians. As noted in the Ma- Given their poor preservation, the CAE terials and Methods, we chose to number the specimens of Zalambdalestes lechei (®gs. premolars as 1 through 4 in this report. 12±14) provided only a few general features Therefore, premolars 4 and 5 of Archibald of lower jaw anatomy for the descriptions by and Averianov (2003) correspond to num- Gregory and Simpson (1926a). In contrast, bers 3 and 4 of our report. The lower incisor the sample in Warsaw and Moscow available count in Kulbeckia is four, whereas that of to Kielan-Jaworowska and Tro®mov (1981) 34 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 included several specimens preserving con- may either re¯ect variation in the sample or siderable detail of the lower jaw, most no- in some cases damage to this region of the tably the left lower jaw of PIN 3143±501. specimen. The angle of the coronoid to the The angle was broken off in this specimen, alveolar margin is approximately 60Њ in PSS- but ``the preserved part indicates that it has MAE 108 (®g. 23) and 55Њ on the right side been in¯ected medially'' (ibid.: 4), also re- of PSS-MAE 129 (®g. 31). A lower angle ported for Barunlestes by Kielan-Jaworow- had been reported previously for Z. lechei: ska (1975a). ca. 45Њ by Gregory and Simpson (1926a) and Four MAE specimens of Zalambdalestes ca. 49Њ in adults and ca. 42Њ in juveniles by preserve lower jaws, PSS-MAE 108, 129, Kielan-Jaworowska and Tro®mov (1981). 135, and 145; in each instance, both right and Among the CAE specimens, the angle is left jaws are in articulation. The ®rst two close to 45Њ in AMNH 21704, but in the ho- specimens show details of the external sur- lotype, 21708, it is higher, approximately 54Њ face only, as the internal is obscured from (®g. 13). preparation (®gs. 11, 23, 31, 33, 39); little of As seen in PSS-MAE 108 (®g. 23) and the jaw structure remains in PSS-MAE 135 129 (®g. 31), the ascending ramus of the (®gs. 30, 38); and until further preparation is mandible has a well-developed masseteric completed, we do not consider the lower fossa that extends to the lower edge of the jaws of PSS-MAE 145. We reconstruct the jaw. It is strongly demarcated anteriorly by a lower jaw in lateral view (®g. 15), address very prominent coronoid crest (masseteric the salient features of external lower jaw crest of Kielan-Jaworowska and Tro®mov, anatomy here, and, for the sake of complete- 1981), which becomes narrower as it nears ness, repeat Kielan-Jaworowska and Tro®- the tip of the coronoid process. A distinct, mov's (1981) observations on the internal but low masseteric line (crest) inferior to the structure. fossa is preserved in PSS-MAE 129 (®g. 31); The lower jaw in Zalambdalestes is elon- the corresponding area is worn in PSS-MAE gate and anteriorly tapering, with two mental 108. There is no indication of a labial man- foramina of unequal size (not clearly pre- dibular foramen at the rear of the base of the served in any MAE specimen), the larger one coronoid crest on the MAE or AMNH spec- below the middle of p3 and the other below imens, or on the high-resolution CT scans of the anterior root of p1, according to Kielan- PSS-MAE 108. Such a foramen has been re- Jaworowska and Tro®mov (1981). The most ported by Kielan-Jaworowska and Dashzev- distinctive aspect of the anterior mandible is eg (1989) for Zalambdalestes lechei and Z. the large root for i1, which extends back to nymbulakensis, a junior synonym of Sorles- a point below at least the last premolar in tes budan according to Nessov et al. (1994). PSS-MAE 108 and 129; as noted above, Fos- For Z. lechei, Kielan-Jaworowska and Dash- towicz-Frelik and Kielan-Jaworowska (2002) zeveg cited a plate of photographs of PIN reported that the root of the lower incisor is 3143±501 in Kielan-Jaworowska and Tro®- open and extends below the p4 and anterior mov (1981: pl. 2). The lateral view of the part of m1. The symphysis extends to the lower jaw in their ®gure 2a shows cracks and front of p3 in PSS-MAE 129 (®g. 39); Kie- a large artifactual opening in the masseteric lan-Jaworowska and Tro®mov (1981) report- fossa. In addition, there does appear to be a ed it reaching as far as the p2. The coronoid foramen behind the coronoid crest at the lev- process is high and its apex is hooklike, with el of the m3 trigonid cusps. As noted by Kie- a strongly concave posterior edge on the lan-Jaworowska and Dashzeveg (1989), the right side of PSS-MAE 129 (®g. 31) and on opening in PIN 3143±501 is situated higher the left side of PSS-MAE 108 (®g. 23). This and is larger than the labial mandibular fo- pro®le is not rendered in previously pub- ramen in Early Cretaceous Prokennalestes. lished ®gures of Zalambdalestes and Barun- As preserved in PSS-MAE 108 (®g. 23), lestes (®gs. 4B, 51B; Kielan-Jaworowska, a low condyloid crest running anteroventrally 1975a: ®g. 2), and ®rsthand preliminary ex- from the condyle toward the coronoid crest amination of the material in the Polish±Mon- divides the masseteric fossa into subequal golian collections suggests the difference parts: a larger, deeper dorsal part and a small- 2004 WIBLE ET AL.: ZALAMBDALESTES 35

Fig. 13. Stereophotographs of the right lower jaw of Zalambdalestes lechei AMNH 21708 in lateral view. er, nearly ¯at ventral part (see also Kielan- Jaworowska and Tro®mov, 1981). A crack Jaworowska and Tro®mov, 1981). The con- separates the angle on the right mandible of dyle in PSS-MAE 108 (®g. 23) and 129 (®g. AMNH 21708 from the ascending ramus 31) is positioned notably high relative to the (®gs. 13, 14). The angle has been reposi- angle. The condyle is markedly broadened tioned and glued following the contours, and transversely, with an extensive convex sur- it shows no medial in¯ection. The angular face dorsally and posteriorly for contact with process in PIN 3143±501, the specimen of the glenoid fossa. Both the medial and lateral Zalambdalestes described by Kielan-Jawo- margins of the articular surface in PSS-MAE rowska and Tro®mov (1981: pl. 1), is com- 108 are drawn into triangular, transversely plete except for its tip, and the stereophoto- oriented processes, the one on the medial graph of the occlusal view appears to show side being much more delicate. a slight medial deviation to the posteroven- The angular process is fully preserved on trally directed process compared with PSS- the left side of PSS-MAE 108 (®gs. 23, 33). MAE 108. This is much less than the more It is distinctively hooklike in lateral outline, medially deviated posteroventral angular similar to that ®gured for Zalambdalestes by process in Barunlestes (Kielan-Jaworowska, Kielan-Jaworowska (®g. 4B; 1975a: ®g. 2), 1975a: pl. 1, ®g. 1e) and Asioryctes (see Kie- although it is even longer. Viewed from be- lan-Jaworowska, 1981: pl. 6). We think that hind or below (®g. 33), the angle shows no most of the descriptions of medially in¯ected signi®cant medial in¯ection (contra Kielan- angles in Cretaceous eutherians are the result 36 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 14. Stereophotographs of the lower jaws of Zalambdalestes lechei AMNH 21708 in left oblique view to see the medial surface of the right ascending ramus.

Fig. 15. Reconstruction of the right lower jaw of Zalambdalestes lechei in lateral view. Dental formula is i3, c, p4, m3, as occurs in PSS-MAE 108 and in ZPAL MgM-I/13, 14, and 16; p2 is lacking in PSS-MAE 129 and in AMNH 21704 and 21708. Mental foramina are reconstructed based on Kielan- Jaworowska and Tro®mov (1981). Abbreviations: an, (mandibular) angle; cc, condyloid crest; coc, coronoid crest; con, (mandibular) condyle; cor, coronoid process; maf, masseteric fossa; mf, mental foramina. 2004 WIBLE ET AL.: ZALAMBDALESTES 37 of de®nitional problems. We follow the ter- or the rugosity also of uncertain meaning minology proposed by SaÂnchez-Villagra and present in Prokennalestes (Kielan-Jaworow- Smith (1997) and agree with these authors ska and Dashzeveg, 1989). that no Cretaceous eutherian has a medially in¯ected angle, a feature fairly widespread SKULL within Metatheria (Rougier et al., 1998). Lagomorphs and some rodents have an angle Skulls are known for two of the CAE that is thickened on its medial surface or bent specimens of Zalambdalestes lechei (AMNH medially, but not to the same extent as in 21704 and 21708). However, with the excep- metatherians. The Cretaceous eutherian that tion of the snout and palate in AMNH 21708 comes closest to the metatherian form of the (®g. 1), there are few details of cranial anat- angle is Montanalestes from the Albian-Ap- omy that are recoverable from either speci- tian of Montana (see Cifelli, 1999). men. Not surprisingly, Gregory and Simp- Kielan-Jaworowska and Tro®mov (1981: son's (1926a) observations on the skull of Z. 4) described the following features of the in- lechei were limited and general. They pro- ternal anatomy of the lower jaw of PIN vided a restoration of the skull in lateral view 3143±501: ``The symphyseal surface is (ibid.: ®g. 16), based largely on the holotype, markedly rugose and is bounded from above which delimits only the premaxillary bone, in the middle part by a ridge. Behind the and illustrated few features beyond the infra- symphysis the surface of the mandibular ra- orbital foramen. mus is slightly swollen below p3 and anterior Van Valen (1964: ®g. 2) presented a new root of m1. On the lower part of the ascend- restoration of the skull of Zalambdalestes in ing ramus of the coronoid process there is a lateral and palatal views said to be ``drawn distinct, oval, rugose swelling, 1.8 mm long and slightly reconstructed by S. B. McDow- and 1.2 mm wide, possibly a remnant of the ell'' redrawn here as ®gure 4A and C. Al- coronoid bone, fused with the dentary. Be- though based on the CAE specimens, this hind and below this swelling there is a ridge restoration provided more sutural details than (medial ¯ange of Kermack et al., 1973), those by Gregory and Simpson. Delimited which extends posteriorly and reaches the were the bones on the palate and in the or- condyle. The mandibular foramen is large, bitotemporal region, but there were no new situated ca. 5.2 mm behind the last molar. accompanying descriptions. Our study of the Extending posteriorly from the mandibular CAE specimens con®rms the sutural details foramen there is a very distinct tear-drop- of four bones (premaxilla, maxilla, lacrimal, shaped fossa, pointed backwards and up- and squamosal) in the reconstruction by Van wards. The fossa is delimited from above by Valen; the remainder is conjectural and does the medial ¯ange. At the anterior part of the not agree with the morphology of the MAE fossa there is a faint groove which extends specimens. posteriorly, parallel to the medial ¯ange and A detailed description of the skull of Za- disappears in the middle length of the fossa.'' lambdalestes lechei based largely on ZPAL Regarding the possible occurrence of the MgM-I/14 and 16 was published in Kielan- coronoid bone suggested by Kielan-Jawo- Jaworowska (1984a). Most of the external rowska and Tro®mov (1981), the type spec- surfaces of the skull were described, with the imen AMNH 21708 (®g. 14), although exception of the basicranium, which was not cracked in this area, as well as the CT scans preserved in any specimens in the Warsaw or of PSS-MAE 108 show no such swelling like Moscow collections. Kielan-Jaworowska in- that described in PIN 3143±501, and else- cluded a fairly detailed reconstruction of the where (Rougier et al., 1998) we have scored skull in ventral view (ibid.: ®g. 1), with the this element as absent for Zalambdalestes. basicranium based on that known in Barun- We do not know the meaning of the swelling lestes (Kielan-Jaworowska and Tro®mov, described by Kielan-Jaworwoska and Tro®- 1980) redrawn here as ®gure 4D. The sutural mov (1981). It is positioned higher up the relations depicted in her reconstruction are coronoid process than the obvious coronoid for the most part not supported by the mor- facet present in Vincelestes (Rougier, 1993) phology preserved in the MAE specimens. A 38 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 16. Reconstruction of the skull of Zalambdalestes lechei in (clockwise from upper left) dorsal, ventral, and right lateral views, illustrating the cranial measurements in table 3. Abbreviations: BBP, breadth of bony palate across M1; BR, breadth of rostrum; CH, height of ascending mandibular ramus at condylar process; IB, interorbital breadth; LR, length of rostrum; MD, depth of mandible at m1; ML, length of mandible; NB, nuchal breadth; ONL, occipitonasal length; PCL, premaxillary-condylar length; PL, palatal length; POL, preorbital length; PPL, postpalatal length; RH, height of ascending mandibular ramus at coronoid process; RL, length of ascending mandibular ramus behind m3; ZB, greatest zygomatic breadth. 2004 WIBLE ET AL.: ZALAMBDALESTES 39 more featureless reconstruction of the skull maxilla is very well preserved, better than in of Z. lechei in lateral view was published any other specimen collected to date, and elsewhere (Kielan-Jaworowska, 1975a: ®g. only the rostralmost tip is missing (®gs. 7, 2A; Kielan-Jaworowska et al., 1979: ®g. 12± 8A). It shows that the premaxilla anterior to 1C) redrawn here as ®gure 4B. Finally, par- the I1 alveolus, which we refer to as the ros- tial endocranial casts of ZPAL MgM-I/14 tral process, is considerably longer than in and 16 were described in Kielan-Jaworowska the reconstructions by Gregory and Simpson (1984b). (1926a: ®g. 16), Van Valen (®g. 4A; 1964: Based on the MAE specimens, we recon- ®g. 2), and Kielan-Jaworowska (®g. 4B; struct the skull of Zalambdalestes lechei in 1975a: ®g. 2A). In lateral view (®g. 26), the dorsal, lateral (with and without the zygo- rostral process lies in a more dorsal plane ma), and ventral view (®gs. 42±44). The than the alveolar margin of the premaxilla skull of Zalambdalestes is notable for its and maxilla. It is also nearly horizontal, large size compared to the other described whereas the snout behind it is bent somewhat Mongolian Cretaceous eutherians (®g. 51; downward. The rostral process projects con- Kielan-Jaworowska, 1984a, 1984c; Novacek siderably farther forward than does the nasal et al., 1997). Certain specimens of Z. lechei bone (as interpreted from PSS-MAE 108 and (e.g., PSS-MAE 108 and 130) range nearly AMNH 21708), producing a much more to 50 mm in length from the anterior apex of oblique external nasal aperture than in pre- the premaxilla to the occipital condyles; cf. vious reconstructions (®g. 44A). The facial Zalambdalestes sp. PSS-MAE 145 has a suture between the premaxilla and maxilla is skull length of more that 60 mm. Barunlestes oblique (®gs. 22, 23, 26, 31). At the alveolar is a close second in size, ranging between 35 margin, it is positioned one-third the distance and 40 mm (Kielan-Jaworowska and Tro®- between the I2 and C, based on PSS-MAE mov, 1980). Kulbeckia kulbecke, the most 108 (®g. 23) and AMNH 21708 (®g. 22). complete specimen of which preserves the Dorsally, it contacts the nasal above the pos- snout and anterior orbit, is probably compa- terior canine root in AMNH 21708 (®g. 22) rable in skull size to Barunlestes. The asio- and PSS-MAE 129 (®g. 31) or anterior to the ryctitheres Kennalestes, Asioryctes, and canine in PSS-MAE 108 (®gs. 11B, 23) and Ukhaatherium range between 26 and 30 mm 130 (®g. 26). Some degree of premaxillary (Kielan-Jaworowska, 1981; personal obs.). expansion is commonly associated with the Daulestes nessovi from the Coniacian of Uz- development of large, long-rooted incisors bekistan is estimated to be just under 20 mm and a wide diastema, but the geometric re- (McKenna et al., 2000). The zalambdalestid lationships of this bone with adjacent skull nasal-facial region in front of the cheekteeth elements varies notably among mammalian is expanded into a long, narrow snout, more groups. Although the premaxilla is exten- so in Zalambdalestes than in Barunlestes or sively exposed in Zalambdalestes, it does not Kulbeckia. The zygomatic arches, unknown extend posteriorly to contact the frontals, as in Barunlestes and Kulbeckia, are slender in rodents and lagomorphs (®gs. 54, 55). and strongly expanded laterally in Zalamb- Most of the nasal bone, including its su- dalestes, and the nuchal and sagittal crests tural relationships, is well preserved in are distinct in Zalambdalestes and Barunles- AMNH 21708 (®g. 17) and PSS-MAE 108 tes. The braincase in Zalambdalestes and Ba- (®g. 18), 129 (®g. 21), and 130 (®g. 19). runlestes is more in¯ated and the mesocra- Only one specimen, PSS-MAE 130, pre- nial region shorter than in the asioryctitheres serves details of the nasal's anterior end (®g. Kennalestes, Asioryctes (Kielan-Jaworow- 19). The rostralmost projection of the nasal ska, 1984a, 1984c), and Ukhaatherium (per- is just off the midline. It extends slightly far- sonal obs.). ther forward than does the premaxilla's con- NASAL-FACIAL REGION: The premaxilla in tribution to the lateral wall of the external Zalambdalestes lechei is expanded, contrib- nasal aperture (®gs. 42, 44A), resulting in uting more than one-third the length of the what Wible and Rougier (2000) termed the preorbital region in lateral view (®g. 44A). nasal overhang of the nares. The nasal does On the left side of PSS-MAE 130, the pre- not extend nearly as far as does the rostral 40 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 17. Stereophotograph of the skull of Zalambdalestes lechei AMNH 21708 in dorsal view, with accompanying line drawing. Gray pattern represents matrix. Abbreviations: fr, frontal; ju, jugal; lac, lacrimal; mx, maxilla; na, nasal; nc, nuchal crest; nfs, nasofrontal suture; pa, parietal; pmx, premaxilla; sc, sagittal crest; sq, squamosal; ssf, subsquamosal foramen; tlc, translacrimal canal. process of the premaxilla in that aperture's the P1±P2 embrasure, they expand to form a ¯oor (®g. 44A). This results in the oblique wide sutural contact with the frontals poste- external nasal aperture mentioned above. riorly and with the lacrimals posterolaterally Near the midpoint in the anterior border of (®gs. 17±21). The nasofrontal suture is irreg- the nasal is a short notch, the anterior nasal ular, best exempli®ed on the left side of PSS- notch (®g. 19). Both the nasal overhang of MAE 108 (®g. 18). Its lateral half is essen- the nares and anterior nasal notches are fea- tially horizontal, at the level of the posterior tures found in primitive mammaliaforms root of the P4. Medially, there is an arcuate (Lillegraven and Krusat, 1991; Wible and process of the nasal overlapping the frontal Rougier, 2000). and extending to the level of the M1, and on In dorsal view, the nasals are narrow and the midline, sharp processes of the frontals elongate for most of their length, but above ®t into a narrow V-shaped notch in the nasals 2004 WIBLE ET AL.: ZALAMBDALESTES 41

PIN 3142±701), the nasal is shown at the anterodorsal edge of the orbit. Our observations of Barunlestes (ZPAL MgM-I/77 and PIN 3142±701) and specimens of Zalambdales- tes, however, reveal that although the nasal is considerably expanded posteriorly, the frontal, not the nasal, is proximate to the orbit. Thus, the prominent anterodorsal rim of the orbit is a composite of the lacrimal (where the rim is most pronounced) and the frontal. A similar arrangement is reported for Kulbeckia (®g. 51C; Archibald et al., 2001; Archibald and Averianov, 2003). The lacrimal in Zalambdalestes is a prominent element with a facial process that is broad and arcuate in PSS-MAE 108 (®g. 18) and 130 (®g. 19), broad and trapezoidal in PSS-MAE 135 (®g. 20), and broad and triangular in AMNH 21708 (®g. 17). The in- trusion of the lacrimal in the facial region also shows some variation; it is more intru- sive in the AMNH 21708 than in PSS-MAE 108, 130, and 135. These specimens, except PSS-MAE 130, preserve a well-developed foramen in the facial process of the lacrimal (®gs. 17, 18, 20), which is discussed below (see Orbitotemporal Region). The maxilla in PSS-MAE 108 and 130 and AMNH 21708 is extensive for most of the length of the posterior rostrum, but is limited dorsally by the development of the nasal and the facial processes of the lacrimal and jugal Fig. 17. Continued. (®gs. 22, 23, 26). The antorbital depression of the maxilla is rather shallow, with an infraorbital foramen (for passage of the infra- in AMNH 21708 (®g. 17) and PSS-MAE orbital nerve and vessels) directly above the 108 (®g. 18). In PSS-MAE 129 (®g. 21) and embrasure between P2 and P3. The infraor- 130 (®g. 19), the nasofrontal contact on the bital foramen is large and subcircular, slight- midline is much ¯atter. The very broad ex- ly larger dorsoventrally than mediolaterally. posure of the nasal isolates the frontal from There is no clearly demarcated antorbital pit contact with the facial moiety of the maxilla. for origin of the snout muscles as is striking- The reconstruction of Zalambdalestes by Van ly characteristic of leptictids and lipotyphlan Valen (1964: ®g. 2) incorrectly shows the insectivorans (Novacek, 1986a). Kielan-Ja- frontal contacting the maxilla (®g. 4A). Na- worowska (1984a) noted that the suture be- solacrimal contact also occurs in the proto- tween the maxilla and jugal was unclear in tribosphenidan Vincelestes and a variety of the Warsaw specimens of Zalambdalestes archaic metatherians and eutherians (Rougier (®g. 4B) (and also in Barunlestes, ®g. 51B), et al., 1998), and it represents a retention of whereas the reconstruction by Van Valen the primitive therian condition in Zalamb- (1964: ®g. 2) has the maxilla excluded from dalestes. Kielan-Jaworowska and Tro®mov the orbital rim by contact between the jugal (1980: 170) reported that the upper rim of and lacrimal (®g. 4A). The sutures in this the orbit in Barunlestes was formed by the region are distinct on the left side of AMNH lacrimal and nasal, and in their ®gure 1 (of 21708 (®g. 22) and PSS-MAE 108 (®g. 23) 42 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 18. Stereophotograph of the skull of Zalambdalestes lechei PSS-MAE 108 in dorsal view, with accompanying line drawing. Gray pattern represents matrix. Abbreviations: at, atlas; cor, coronoid process; fr, frontal; lac, lacrimal; mx, maxilla; na, nasal; nc, nuchal crest; pa, parietal; pmx, premaxilla; pop (br), postorbital process (broken); sc, sagittal crest; sq, squamosal; ssf, subsquamosal foramen; tl, temporal line; tlc, translacrimal canal. and 130 (®g. 26), and they con®rm Van Val- oblique part in the anterior three-fourths and en's reconstruction. The jugal is a sizable el- a more horizontal part in the posterior one- ement; it contacts the lacrimal and thus forms fourth. Only the anteriormost part of the the inferior part of the orbital rim. It also maxillo-jugal suture is preserved in AMNH forms most of the anterior part of the zygo- 21708 (®g. 22). matic process in ventral view (®gs. 33, 35). PALATE: Poorly known from previously The posterior edge of the short zygomatic described specimens of Zalambdalestes (see process of the maxilla is at the level of the ®g. 32), the palatal process of the premaxilla metacone of M2 (®g. 35). The suture be- is very well preserved on the left side of tween the maxilla and jugal is arcuate in PSS-MAE 130, with only the rostralmost tip PSS-MAE 108 (®g. 23), but is more angular missing (®gs. 7, 8A). The rostral process of in PSS-MAE 130 (®g. 26), divisible into an the premaxilla, the portion anterior to the I1 2004 WIBLE ET AL.: ZALAMBDALESTES 43

(®g. 11A), this depression was likely the rest- ing place for the tip of that tooth. The interpremaxillary suture on the palate, as interpreted from PSS-MAE 130 (®gs. 7, 8A) and AMNH 21708 (®g. 32), extends from the tip of the rostrum to the level of the back edge of the I1 alveolus. From that point, based on these specimens plus PSS-MAE 108 (®gs. 11, 33), the posterior border of the premaxilla runs obliquely, encountering the alveolar margin between the I2 and C or I3 (when present). This resembles the premaxillary-maxillary suture illustrated for AMNH 21708 by Gregory and Simpson (1926a: ®g. 14), but differs from the reconstructions by Van Valen (®g. 4C; 1964: ®g. 2) and Kielan- Jaworowska (®g. 4D; 1984a: ®g. 1). The latter authors extend the interpremaxillary suture more posteriorly, which results in a more transverse premaxillary-maxillary suture. The exact morphology of the premaxillary- maxillary suture at the alveolar margin and on the face in PSS-MAE 130 is unclear due to breakage (®gs. 7, 8A). As preserved, the I3 is wholly within the maxilla, but as mentioned above, a facet on the maxilla may have contained a process of the premaxilla contributing to the anterior rim of the I3 alveolus. We think this interpretation unlikely, because PSS-MAE 108 (®gs. 11A, 33) and AMNH 27108 (®g. 32), in which this region Fig. 18. Continued. is well preserved, have no such process on the premaxilla. Within the premaxillary-maxillary suture at the level just posterior and alveolus, is longer and less rounded than in medial to the alveolus of I2 is a small, elon- the reconstruction by Kielan-Jaworowska gate opening on the right side in PSS-MAE (®g. 4D; 1984a: ®g. 1). The lateral edge of 108 (®gs. 11A, 33) and on the left in PSS- the rostral process immediately anterior to I1 MAE 130 (®gs. 7, 8A). We interpret these has a sharp, longitudinal crest, delimiting the openings as the incisive foramen, previously palatal and facial components of the rostral unknown for Zalambdalestes (®g. 4C, D) or process (®gs. 7, 8A). A similar crest is found Barunlestes, although they are unusual in on the premaxilla in extant armadillos, where their lateral position and their posteroventro- it marks the lower limit of the attachment of medial orientation. Incisive foramina gener- a muscle inserting into the skin of the nose ally are positioned nearer the midline and (Wible and Gaudin, in prep.), the nasalis of face ventrally or anteroventrally in mam- Uekermann (1912). Medial to the crest in Za- mals, even in forms (e.g., rodents, lago- lambdalestes, the palatal component of the morphs) with large premaxillae containing rostral process presents a concave surface, roots for large incisors (Starck, 1995). Inci- deepest anteriorly, that appears continuous sive foramina even nearer the alveolar mar- across the midline (®gs. 7, 8A). There is a gin than those in PSS-MAE 108 and 130 oc- large opening in this depression in PSS-MAE cur in some forms (e.g., the soricid Scutiso- 130, but it is an artifact. Based on the posi- rex, CM 86647), but we are not aware of any tion of the elongated i1 in PSS-MAE 108 forms that have incisive foramina with a sim- 44 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 19. Stereophotograph of the skull of Zalambdalestes lechei PSS-MAE 130 in dorsal view, with accompanying line drawing. Gray pattern represents matrix. Abbreviations: ch, cerebral hemisphere; fr, frontal; ju, jugal; lac, lacrimal; mx, maxilla; na, nasal; naf, nasal facet on frontal; ob, olafactory bulb; pa, parietal; pal, palatine; pmx, premaxilla; sq, squamosal; ssf, subsquamosal foramen; sss, superior sagittal sinus; ts, transverse sinus; ver, vermis of cerebellum. ilar orientation to those in PSS-MAE 108 concave surfaces on either side of the mid- and 130. line. Anteriorly, they taper to a narrow point- The palatal processes of the maxillae are ed end at the level of the I2 alveolus that is nearly complete in PSS-MAE 130, the major inserted into a V-shaped notch between the damage being an artifactual hole immediate- two premaxillae. As evidenced by PSS-MAE ly anterior to the palatine bone (®gs. 8A, 35. 108 and AMNH 21708 (®g. 32), there is a The maxillae form two elongate, shallow, low, raised ridge on the anterior part of the 2004 WIBLE ET AL.: ZALAMBDALESTES 45

ble, with a smaller posterolateral opening separated by a narrow bridge from a larger anteromedial opening, which has a short, faint groove extending forward from it. There is a major palatine foramen on the right side of AMNH 21708 (®g. 32). As preserved, it is a single large opening and is even more posterior than in PSS-MAE 130, opposite the protocone of P4 (®gs. 4C, 32). A second smaller opening appears to lie opposite the protocone of M1 (not ®gured by Van Valen). The nature of this second aperture is unclear (a second major palatine foramen, an accessory palatine foramen, or artifact); PSS-MAE 130 shows no such opening, but its palate is damaged in this region (®gs. 8A, 35). The horizontal portion of the palatine bone has been poorly known for Zalambdalestes, but most of it is well preserved in PSS-MAE 130; the exception is the anterior portion, which is missing as is the posteromedial portion of the maxillae (®gs. 8A, 35). As reconstructed here, the palatal processes of the palatines are proportionally very small (®g. 43), smaller than the elements reconstructed by Kielan-Jaworowska (®g. 4D; 1984a: ®g. 1) for Zalambdalestes based on Barunlestes.It also does not appear to contain any accessory palatine foramen (lesser palatine foramen of Kielan-Jaworowska) near its anterior margin or a more central location, such as those included in the reconstructions in Van Valen (®g. 4C; 1964: ®g. 2) and Kielan-Jaworow- Fig. 19. Continued. ska (®g. 4D; 1984a: ®g. 1). The lateral suture with the maxilla can be discerned on the left side of PSS-MAE 130 (®gs. 8A, 35). It runs intermaxillary suture that ends at the level of longitudinally medial to the molars. Only the the canine. Only the rostralmost part of the posterior portion of the suture itself, between intermaxillary suture in PSS-MAE 130 the minor palatine foramen (posterior pala- shows this ridge; behind that the left and tine foramen of Kielan-Jaworowska, 1984a) right maxillae have been separated postmor- and the M2, is preserved. Anterior to this to tally to a slight extent (®gs. 7, 8A). Based on the level of the M1 protocone, there is a ZPAL MgM-I/14 and 16, Kielan-Jaworow- ridge on the maxilla that indicates where the ska (1984a) reported a major palatine fora- palatine abutted, but that bone is missing in men (her greater palatine foramen) in the this interval. We were unable to identify the maxilla opposite the protocone of P3 with a palatines' anterior suture with the maxillae, very short groove extending forward from it at least in part because of damage that re- (®g. 4D). The major palatine foramen in sulted in a gaping hole. We tentatively re- PSS-MAE 130 differs in two regards (®gs. construct that suture near the anteriormost 8A, 35). First, it is slightly more posterior, preserved limit of the palatine, at the level more so on the left than on the right, opposite of the mesial edge of M1 (®g. 43). A raised the posterior part of the P3. Second, it is dou- ridge runs the length of the preserved inter- 46 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 20. Stereophotograph of the skull of Zalambdalestes lechei PSS-MAE 135 in dorsal view, with accompanying line drawing. Gray pattern represents matrix; parallel lines are damaged surfaces. Ab- breviations: fr, frontal; lac, lacrimal; lacf, lacrimal foramen; ma, mandible; mx, maxilla; na, nasal; nc, nuchal crest; pa, parietal; paf, parietal facet on frontal; pop, postorbital process; sc, sagittal crest; sq, squamosal; tl, temporal line; tlc, translacrimal canal. palatine suture, which is ®lled with matrix, lan-Jaworowska (®g. 4D; 1984a: ®g. 1), and expands laterally into the strong post- which places the maxilla on the posterior palatine torus (®gs. 35, 43). Kielan-Jawo- border of the foramen, and of Van Valen (®g. rowska (1984a) reported the postpalatine to- 4C; 1964: ®g. 2), which shows only a pos- rus as very faint based on ZPAL MgM-I/14 terior palatine notch, the condition preserved and 16, the condition scored for Zalambda- in AMNH 21708 (®g. 32) but probably the lestes by Rougier et al. (1998) in their phy- result of damage. The minor palatine fora- logenetic analysis. In PSS-MAE 130, im- men in life was slightly smaller than as mediately lateral to the postpalatine torus and shown on the left side of PSS-MAE 130, in medial to M3, is a large, oval opening, the which the part of the maxilla and palatine minor palatine foramen, which communi- forming the anterior border are damaged cates directly with the anteroventral portion (®gs. 8A, 35). Anteromedial to the minor of the orbit (®g. 35). The bones forming the palatine foramen in PSS-MAE 130, in the foramen are clearly seen on the left side of anterolateral surface of the base of the post- PSS-MAE 130. Anteriorly, medially, and palatine torus is a small, anteriorly directed, posteromedially, it is the palatine, laterally circular foramen of uncertain function. Pre- the maxilla, and posteriorly the pterygoid. sent bilaterally, this aperture seems too far This contrasts with the reconstruction of Kie- posteriorly positioned to be an accessory pal- 2004 WIBLE ET AL.: ZALAMBDALESTES 47

are preserved in PSS-MAE 108, 130, and 135, as well as in AMNH 21708. The lacrimal is a large element at the anterodorsal apex of the orbit. In addition to its facial process described above, the lacrimal forms a large wedge in the anterior wall of the orbit, based on the left side of PSS-MAE 108 (®g. 24), 130, and 135. Its contacts within the orbit are with the maxilla inferiorly and the frontal medially. The suture with the maxilla, preserved in PSS-MAE 108 (®g. 24) and 135, is essentially straight, except at its lateral terminus where is runs obliquely dorsally. At the medial edge of the maxillo-lacrimal suture is the maxillary foramen, the posterior entrance into the infraorbital canal, which is a transversely oriented, elongate, oval aperture (®g. 24). No specimen preserves the entire suture with the frontal, but enough is preserved between PSS-MAE 108 (®g. 24), 130, and 135 to say that the suture was largely vertical. Two lacrimal foramina are preserved in a shallow depression just inside the orbital rim above the suture between the lacrimal and maxilla on the left side in Fig. 20. Continued. PSS-MAE 108 (®g. 24) and 135. The orbital rim lateral to the more superior lacrimal foramen is thickened and bears a weak lacrimal atine foramen. Wible (2003) reported similar tubercle (®g. 23; also in AMNH 21708, ®gs. foramina piercing the postpalatine torus in 4A, 19; see Van Valen, 1964: ®g. 2). Gregory the didelphid Monodelphis. and Simpson (1926a) reported only a single ORBITOTEMPORAL REGION: Virtually noth- lacrimal foramen (but see below). Preserved ing about the orbit was known from the CAE on both sides in PSS-MAE 108 (®g. 24) and specimens of Zalambdalestes (see ®g. 19), 135, dorsomedial to the lacrimal foramina is according to Gregory and Simpson (1926a). another aperture within the lacrimal some- The reconstruction by Van Valen (®g. 4A; what more recessed from the orbital rim; the 1964: ®g. 2) does include sutures in the orbit, corresponding part of the lacrimal is missing but we cannot identify or con®rm these on in PSS-MAE 130. This oval foramen runs the CAE or MAE specimens. The Warsaw through a short canal that opens on the facial material has provided information only about process of the lacrimal. The facial opening the principal orbital foramina (Kielan-Jawo- of this canal is just outside the orbital rim in rowska, 1984a). Four MAE specimens, PSS- PSS-MAE 108 (®gs. 18, 23), whereas it is MAE 108 (®gs. 23±25), 129 (®g. 31), 130 separated by a wider bridge of bone from the (®gs. 26±29), and 135 (®g. 30), preserve as- orbital rim in PSS-MAE 135 (®gs. 20, 30). pects of the orbital region, and between This canal was discovered upon restudy of them, most features can be recognized, al- the left side of AMNH 21708 (®gs. 17, 22), though not all sutures can be reconstructed with a facial aperture resembling that in PSS- with total certainty. The anterior orbit is best MAE 135. We think the orbital aperture of preserved in PSS-MAE 108 and 135. The this canal was mistakenly identi®ed as the posterior orbit is best represented in PSS- lacrimal foramen by Gregory and Simpson MAE 130, although the identi®cation of (1926a); the part of the lacrimal bone show- some sutures is confounded by numerous ing two lacrimal foramina in PSS-MAE 108 cracks. Finally, aspects of the temporal fossa and 135 is not preserved in AMNH 21708. 48 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 21. Stereophotograph of the skull of cf. Zalambdalestes sp. PSS-MAE 129 in dorsal view, with accompanying line drawing. Part of the endocranial surface of the petrosal is exposed. Gray pattern represents matrix; parallel lines are damaged surfaces. Abbreviations: fr, frontal; mx, maxilla; na, nasal; pe, petrosal; pmx, premaxilla.

The meaning of this canal through the lac- 1989). Rather than the frontal bone, these rimal is uncertain, as no such structure exists nerves and vessels may have been enclosed among other mammals (Gregory, 1920; in the lacrimal in Zalambdalestes. Interest- Muller, 1934; personal obs.). Some elephant ingly, the frontal bone and postorbital pro- shrews (e.g., Macroscelides proboscidens cess (see below) are situated fairly close to CM 40789) have a small foramen into the the facial aperture of this canal in PSS-MAE facial process of the lacrimal that must serve 108 (®g. 18) and 135 (®g. 20). For descrip- a nutritive function, because it has no orbital tive purposes, we coin the term ``translacri- aperture. In extant placentals, a variety of mal canal'' for the structure in Zalambdales- nerves and vessels cross the orbital rim to tes. After our discovery of the translacrimal reach the face (Sisson, 1910; Greene, 1963; canal in Zalambdalestes, Archibald and Av- Evans, 1993). The only ones to be enclosed erianov (2003) reported a very similar struc- in bone in some forms are the frontal nerves ture for Kulbeckia (®g. 51C). The only sig- and vessels, but this is invariably in the fron- ni®cant difference between the two is that the tal bone (Sisson, 1910; Williams et al., passageway in Kulbeckia is much nearer the 2004 WIBLE ET AL.: ZALAMBDALESTES 49

113) noted ``numerous foramina alveolaria posteriora, in which fragments of molar roots are visible'' in Zalambdalestes. A few such small foramina are present in the maxilla of PSS-MAE 135, but the molar roots are not exposed. At the anterior apex of the orbit, as stated above, the maxilla forms the ¯oor and the lacrimal the roof of the maxillary foramen, the large posterior opening into the infraorbital canal. Based on the left side of PSS-MAE 108, the medial aspect of this aperture is formed by a third element, which in fact appears to form the bulk of the anterior and medial wall of the orbit (®g. 24). We identify this element as the frontal (see below). Extending posteriorly from the maxillary foramen is an elongate trough in the orbital wall, preserved on the left side of PSS- MAE 108 (®g. 24) and on the right side of PSS-MAE 135. The swollen maxilla forms the ventral aspect of this trough, but the bulk of this feature is within the element described above as the frontal. Kielan-Jaworowska (1984a) identi®ed this element as palatine based on ZPAL MgM-I/14, but PSS-MAE 108 (®g. 24) and 135 have no preserved sutures that delimit this from what is clearly frontal more dorsally in the orbit. At the posterior terminus of this trough is a large aperture in PSS-MAE 108 (®g. 24), in the same position as the small opening in ZPAL MgM-I/14 that Kielan-Jaworowska (1984a) identi®ed as the sphenopalatine foramen. We Fig. 21. Continued. agree, but note that the aperture in PSS-MAE 108 differs in that it is elongated (®g. 24) and partially divided into a smaller, more anteri- probable suture with the jugal and is there- orly directed anteroventral foramen and a fore farther removed from the postorbital larger, more medially directed posterodorsal process of the frontal. foramen, which we think transmitted the ma- The maxilla in PSS-MAE 108 (®g. 24), jor palatine nerves and vessels to the palate 130 (®g. 27), and 135 is limited to the an- and the caudal nasal nerves and vessels to teroventral part of the orbit and shows ap- the nasal cavity, respectively. The dog, for preciable in¯ation over the crypt that houses example, has two separate foramina, which the cheekteeth. In PSS-MAE 130, the tips of are termed the caudal palatine and spheno- the left molar roots are exposed and project palatine foramina (Evans, 1993). Forming into the orbit dorsal to the maxilla (®g. 27); the anteroventral border of the foramen the specimen's right side has not been transmitting the major palatine nerves and cleared of matrix in this area. It is likely that vessels in PSS-MAE 108 is the maxilla (®g. the molar roots were visible during life in 24). The palatine completes the ventral bor- PSS-MAE 130, with the apertures transmit- der of that foramen as well as that for the ting alveolar nerves, but the current exposure caudal nasal nerves and vessels. The frontal is chie¯y the result of postmortem dorsoven- appears to be the only other element contrib- tral crushing. Kielan-Jaworowska (1984a: uting to the borders of the two foramina (see 50 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 22. Stereophotograph of the skull of Zalambdalestes lechei AMNH 21708 in lateral view, with accompanying line drawing. Gray pattern represents matrix. Abbreviations: as, alisphenoid; C, upper canine (broken); con, (mandibular) condyle; fr, frontal; I2, upper second incisor (broken); iof, infraorbital foramen; ju, jugal; lac, lacrimal; M1, upper ®rst molar; M2, upper second molar; M3, upper third molar; mx, maxilla; na, nasal; P3, upper third premolar; P4, upper fourth premolar; pa, parietal; pgp, postglenoid process; pmx, premaxilla; ppr/ptp, paroccipital process/posttympanic process; smf, suprameatal foramen; sq, squamosal; ssf, subsquamosal foramen; tlc, translacrimal canal. 2004 WIBLE ET AL.: ZALAMBDALESTES 51 below). Posteroventral to the sphenopalatine The posterior contacts of the frontal are foramen in PSS-MAE 108 is a large notch not as well preserved. Behind the palatine, between the maxilla and palatine. Based on the frontal abuts in succession the orbito- the left side of PSS-MAE 130, we know this sphenoid, alisphenoid, and parietal (®g. 44A, notch is closed by the pterygoid posteriorly B). The area of contact between the frontal to form the large minor palatine foramen and the anterior edge of the orbitosphenoid (®gs. 8A, 27, 35). is preserved in only one specimen, PSS- As interpreted here, the frontal is the larg- MAE 130 (®g. 29). However, identi®cation est bone in the orbitotemporal region (®g. of a suture is hindered by numerous cracks 44A, B), although its contribution is not pre- here. We think that the anterior suture be- served intact in any MAE specimen. The left tween the frontal and the orbitosphenoid lies side of PSS-MAE 108 preserves the most, at a level about halfway between the optic with the only parts missing being in the vi- and ethmoidal foramina. Supporting this in- cinity of the lacrimal and orbitosphenoid (®g. terpretation is PSS-MAE 130, in which the 24). Based on PSS-MAE 108, the frontal ap- posterodorsal half of the frontal is missing pears to be the only element in the medial from both sides (®gs. 26, 29) and the left wall of the anterior orbit. It is delimited by orbitosphenoid preserves a facet along its en- sutures from the lacrimal anteriorly, the max- tire dorsal aspect less than halfway up the illa ventrally (between the maxillary and orbital wall indicating where the frontal sphenopalatine foramina), and the palatine overlaid it (®g. 27). This facet shows that the ventrally (posterior to the sphenopalatine fo- dorsal suture between the orbitosphenoid and ramen). It is possible that what we interpret frontal was slightly concave inferiorly. On to be frontal dorsal to the palatine in PSS- the specimen's right side, the anterior end of MAE 108 might contain an additional small this facet curves ventrally a short distance element, although it is not our preferred re- posterior to a major vertical crack, about construction. The frontal has cracks in it run- halfway between the ethmoidal and optic fo- ning dorsally and posteriorly from the sphe- ramina (®g. 26). The ethmoidal foramen lies nopalatine foramen. The dorsal crack extends anterior to this crack, apparently entirely for about two-thirds the height of the orbit within the frontal; the optic foramen is pos- and is truly an artifact. However, the poste- terior to this crack within the orbitosphenoid. rior crack, which is irregular but roughly hor- Little information on the contact between the izontal, might delimit a narrow quadrangular frontal and alisphenoid is preserved. Only element between the frontal and palatine, the posterior part of the fronto-alisphenoid posterior to the sphenopalatine foramen. If suture shows on the left side of PSS-MAE this element is not part of the frontal, then it 108, at the juncture of these bones with the is an unusual anterior process of the orbito- parietal. At their suture, the dorsal surface of sphenoid. Unfortunately, continuity with the the alisphenoid overlies the frontal. Most of orbitosphenoid cannot be established in PSS- the dorsal surface of the alisphenoid is pre- MAE 108 because of damage. PSS-MAE served on the left side of AMNH 21708, but 130, the only other specimen preserving this the fronto-parietal suture is unclear here (®g. region, has numerous cracks on both sides 22). However, the frontal must have contact- (®gs. 26±29), but it does not have a horizon- ed the alisphenoid, because the large crack tal crack resembling that in PSS-MAE 108. along the anterior aspect of the alisphenoid What is preserved on the left side of PSS- is within the frontal bone dorsally. MAE 130 is an oblique crack that delimits a Several major orbital foramina are either small triangular element dorsal to the pala- within the frontal or between the frontal and tine (®g. 27). This element might be an un- another element (®g. 44B). The contributions usual anterior process of the orbitosphenoid, of the frontal to the maxillary and spheno- with a different shape than the larger qua- palatine foramina have been described drangular element in PSS-MAE 108 (®g. 24), above. In PSS-MAE 130, at a level posterior or the elements in both specimens are part of to the minor palatine foramen, there is a large the frontal. The latter is our preferred recon- opening more than halfway up the orbital struction (®g. 44A, B). wall, which we identify as the ethmoidal fo- 52 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 23. Stereophotograph of the skull of Zalambdalestes lechei PSS-MAE 108 in left lateral view, with accompanying line drawing. Gray pattern represents matrix. Abbreviations: an, (mandibular) angle; at, atlas; ax, axis; C, upper canine; c, lower canine; ec, ectotympanic; fr, frontal; I1, upper ®rst incisor; I2, upper second incisor; i1, lower ®rst incisor; i2, lower second incisor; iof, infraorbital foramen; ju, jugal; lact, lacrimal tubercle; mx, maxilla; na, nasal; P1, upper ®rst premolar; P2, upper second pre- 2004 WIBLE ET AL.: ZALAMBDALESTES 53 ramen (®gs. 26, 27, 29). Interpreted to be interpreted as an artifact. Another aperture within the frontal (see above), this oval ap- associated with the frontal is located poster- erture is signi®cantly larger on the right side, odorsal to the sphenopalatine foramen, at the as a result of damage (breakage on the right level of the minor palatine foramen on the and crushing on the left). An ethmoidal fo- left side of PSS-MAE 108. This oval opening ramen is similarly situated on the right side is in the horizontal crack described above of PSS-MAE 135 and is comparable in size that we interpret to be within the frontal (®gs. to that on the left side of PSS-MAE 130. The 23, 24). Given that this opening is lacking in anterior portion of the ethmoidal foramen is PSS-MAE 130 (®gs. 26, 27), we interpret it preserved on the left side of PSS-MAE 108, as an artifact. along the broken posterior edge of the frontal The palatine has a long, narrow, roughly bone (®g. 24), but the incidence of this fo- quadrangular contribution to the orbital mo- ramen in the remaining specimens cannot be saic in Zalambdalestes, forming the medial evaluated. This portion of the orbit was not wall of the minor palatine foramen and ex- preserved in the specimens described by Kie- tending between the pterygoid inferiorly, ali- lan-Jaworowska (1984a). An anterior open- sphenoid posteriorly, frontal superiorly, and ing of the orbitotemporal canal (sinus canal maxilla anteriorly in PSS-MAE 108 and 130 foramen) was identi®ed by Kielan-Jawo- (®gs. 24, 27). Our estimate is that the pala- rowska (1984b: pl. 30, ®g. 1a) in a stereo- tine's contribution in the orbit, as in the pal- photograph of ZPAL MgM-I/16 anterodorsal ate, is not very extensive (®g. 44B). Distinct to what we interpret as the superior orbital sutures separate the palatine and frontal at ®ssure based on PSS-MAE 130. We have and posterior to the sphenopalatine foramen used this location for the foramen in our re- on the left side of PSS-MAE 108 (®gs. 23, construction, at the junction of the frontal, 24) and the palatine and the pterygoid in alisphenoid, and orbitosphenoid (®g. 44B). PSS-MAE 130 (®g. 27). The contact between The only specimen with a potential opening the palatine and the anterior process of the in this position is the left side of PSS-MAE alisphenoid is preserved on the left side of 130, which has an irregular (possibly artifac- PSS-MAE 130, along a major vertical crack tual?) opening at the junction of the orbito- running through the entire side wall of the sphenoid and alisphenoid, posterodorsal to braincase (®g. 27). the optic foramen (®g. 27). Damage to the Based on the left side of PSS-MAE 130, right side of PSS-MAE 130 has exposed the the pterygoid forms the posterior border of orbitotemporal canal, preserved as a small, the minor palatine foramen and extends pos- anteriorly directed, artifactual opening about teriorly ®rst as a near horizontal lamina that halfway up the temporal fossa, at the level quickly becomes near vertical to become the of the foramen rotundum, presumably be- principal component of the thin entoptery- tween the alisphenoid and parietal, with a goid crest (®g. 35). In addition to contribut- groove extending from it (®g. 29). On the left ing to the entopterygoid crest, the pterygoid side of PSS-MAE 108, there is an oval open- contributes to the medial surface of the base ing slightly more posteriorly positioned, near of the more posterolaterally situated ectop- the fronto-parietal-alisphenoid juncture. This terygoid crest, sending a triangular ¯ange aperture is not the anterior opening of the that underlies the alisphenoid (®gs. 35, 36, orbitotemporal canal, because it is located 37A, B). The entopterygoid crest is well pre- too far posteriorly and opens directly later- served on both sides of PSS-MAE 108 (®gs. ally rather than anteriorly. Although the edg- 33, 34A) and on the right side of 130 (®g. es of this aperture appear to be natural, it is 35). In lateral view, it is shaped like an ob-

← molar; p1, lower ®rst premolar; p2, lower second premolar; p3, lower third premolar; pa, parietal; pal, palatine; pgp, postglenoid process; pmx, premaxilla; ppr/ptp, paroccipital process/posttympanic process; pt, pterygoid; ptc, posttympanic crest; ptf, posttemporal foramen; smf, suprameatal foramen; sq, squamosal; tlc, translacrimal canal. 54 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 24. Stereophotograph of the left orbit of Zalambdalestes lechei PSS-MAE 108 in oblique lateral view, with accompanying line drawing. Gray pattern represents matrix; parallel lines are damaged surfaces. Abbreviations: an, (mandibular) angle; ef, ethmoidal foramen; fr, frontal; ju, jugal; lac, lacrimal; lacf, lacrimal foramen; ma, mandible; mx, maxilla; mxf, maxillary foramen; pal, palatine; spf, sphenopalatine foramen; tlc, translacrimal canal; tr, trough. tuse triangle, with the posterior side being posteroventral tip is the hamulus, which is the shortest. The lateral surface of the crest pointed in PSS-MAE 108 (®gs. 33, 34A) and is concave for the attachment of the medial more hooklike in 130, although possibly pterygoid muscle (®gs. 26, 29). The crest's damaged (®gs. 35, 36). 2004 WIBLE ET AL.: ZALAMBDALESTES 55

Fig. 25. Stereophotograph of the skull of Zalambdalestes lechei PSS-MAE 108 in right lateral view.

Preserved in only PSS-MAE 130 and preserved on both sides of PSS-MAE 130 more completely on the left side, the orbi- immediately dorsal to the superior orbital ®s- tosphenoid is a small, roughly quadrangular sure, with the latter bone overlying the for- element that reaches only halfway up the or- mer. The orbitosphenoid's dorsal suture with bital wall (®g. 44B). Its anterior contact with the frontal has already been described. Pre- the frontal cannot be precisely distinguished, served on both sides in PSS-MAE 130 are but must lie between the ethmoidal and optic two major foramina (®gs. 27, 29), one en- foramina, the former being enclosed within tirely within the orbitosphenoid and the other the frontal and the latter within the orbito- between that bone and the alisphenoid. The sphenoid. Inferiorly, the left side of PSS- former, the optic foramen (for the optic nerve MAE 130 preserves a narrow contact, con- and ophthalmic artery), is elongate, anteri- cave inferiorly, between the orbitosphenoid orly directed, and located in the anteroventral and the anterior process of the alisphenoid aspect of the orbitosphenoid, dorsomedial to (®g. 27). Posteriorly, part of the suture be- the midpoint of the entopterygoid crest. The tween the orbitosphenoid and alisphenoid is latter, the superior orbital ®ssure (for the oc- 56 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 2004 WIBLE ET AL.: ZALAMBDALESTES 57 ulomotor [III], trochlear [IV], abducens [VI], lambdalestes. The superior orbital ®ssure and and ophthalmic [V1] nerves, and the oph- foramen rotundum are recessed between the thalmic veins), is a much larger aperture, lateral braincase wall and the obliquely ori- more anterolaterally directed, and roughly ented ectopterygoid crest, the dorsal surface heart-shaped with the apex pointing posteri- of which is formed by the alisphenoid and orly. It is situated in the posteroventral aspect provides attachment area for the external of the orbitosphenoid, with that bone form- pterygoid muscle. Although thin, the ectop- ing the medial wall and the alisphenoid the terygoid crest is well preserved bilaterally in lateral. Neither the optic foramen nor the su- PSS-MAE 108 (®gs. 33, 34) and 130 (®gs. perior orbital ®ssure have been described 35, 37A, B). As with the entopterygoid crest, previously for Zalambdalestes, although both the ectopterygoid is shaped like an obtuse apertures are visible in a stereophotograph of triangle with the posterior side the shortest ZPAL MgM-I/16 published in Kielan-Jawo- (®gs. 26, 29). A narrow anterior process ex- rowska (1984b: pl. 30). tends forward from the main body of the ali- The alisphenoid is not completely presphenoid between the orbitosphenoid and served in any specimen, but the bulk of its pterygoid on both sides in PSS-MAE 130 contribution to the temporal fossa can be re- (®g. 27). The better preserved left side shows constructed from both sides of PSS-MAE a clear contact between the anterior process 130 (®gs. 26, 27, 29) and the left sides of and palatine. A similar anterior process of the PSS-MAE 108 and AMNH 21708 (®g. 22). alisphenoid in contact with the palatine is Like the orbitosphenoid in front of it, the ali- found in a various extinct and extant therians sphenoid reaches roughly halfway up the (Muller, 1934; Novacek, 1986a; Hershkovitz, braincase wall (®g. 44A, B), based on PSS- 1992; Wible, 2003). MAE 108 and AMNH 21708. However, the Along the orbital rim, the left frontal of alisphenoid is a much more substantial ele- PSS-MAE 135 has a short, triangular post- ment than the orbitosphenoid, more than orbital process directed laterally and slightly twice as long in the anteroposterior dimen- posteriorly, just behind the suture with the sion. The alisphenoid's contacts with the or- lacrimal (®g. 20). The base of this process is bitosphenoid and palatine anteriorly, the damaged but identi®able on the right side of frontal superiorly, and the pterygoid inferi- PSS-MAE 108 (®g. 18) and on the left side orly have already been described. Its poste- of AMNH 21708 (®g. 17). The postorbital rior contact with the parietal and squamosal process has not been noted previously for is immediately anterior to the zygomatic pro- Zalambdalestes (®g. 4A, B), but this is likely cess of the squamosal and glenoid fossa, the result of specimen damage. On its dorsal based on the left sides of PSS-MAE 108 and roof, the frontal in PSS-MAE 108, 129, 135, 130 (®g. 26). Immediately posterior to the and AMNH 21708 shows a distinct but low superior orbital ®ssure, which lies between temporal line that forms the lateral edge of the alisphenoid and orbitosphenoid, is a the skull roof behind the postorbital process smaller, anteriorly directed foramen entirely (®gs. 17, 18, 20, 21). At a level just anterior within the alisphenoid (®gs. 27, 29). This is to the ethmoidal foramen, the temporal line the foramen rotundum (for the maxillary leaves the lateral edge of the skull roof and nerve [V2]), previously unknown for Za- runs posteromedially to the midline of the

← Fig. 26. Stereophotograph of the skull of Zalambdalestes lechei PSS-MAE 130 in left lateral view, with accompanying line drawing. Gray pattern represents matrix. Abbreviations: as, alisphenoid; C, upper canine; ecpc, ectopterygoid crest; ef, ethmoidal foramen; fr, frontal; I1a, upper ®rst incisor alveolus; I2a, upper second incisor alveolus; iof, infraorbital foramen; lac, lacrimal; M1, upper ®rst molar; M2, upper second molar; M3, upper third molar; mx, maxilla; P2, upper second premolar; P3, upper third premolar; P4, upper fourth premolar; pa, parietal; pgp, postglenoid process; pmx, premaxilla; ppr/ ptc, paroccipital process/posttympanic process; pt, pterygoid; ptc, posttympanic crest; ptf, posttemporal foramen; smf, suprameatal foramen; sq, squamosal; ssf, subsquamosal foramen. 58 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 27. Stereophotograph of the left orbit of Zalambdalestes lechei PSS-MAE 130 in oblique lateral view, with accompanying line drawing. Gray pattern represents matrix. Abbreviations: ap, anterior process of alisphenoid; ef, ethmoidal foramen; fr, frontal; fro, foramen rotundum; ju, jugal; mpf, minor palatine foramen; mx, maxilla; opf, optic foramen; os, orbitosphenoid; otc?, orbitotemporal canal?; pal, palatine; pt, pterygoid; sof, superior orbital ®ssure; sq, squamosal; V3br, foramina for branches of mandibular division of trigeminal nerve. skull. Here the right and left temporal lines fronto-parietal suture parallels, lying lateral converge to form a sagittal crest just anterior to, the temporal line, such that the frontals to the fronto-parietal suture. Based on PSS- form a V-shaped posterior process ®t be- MAE 108 and 135 and AMNH 21708, the tween inverse V-shaped anterior processes on 2004 WIBLE ET AL.: ZALAMBDALESTES 59

Fig. 28. Stereophotograph of the left orbit of Zalambdalestes lechei PSS-MAE 130 in oblique lateral view, showing the roots of the left molars projecting through the ¯oor of the orbit. the parietals (®gs. 17, 18, 20). The parietal cernible. Most of the posterior skull roof is overlaps the frontal to a considerable degree; lacking in PSS-MAE 130, although some the anterior aspect of this bone is lost on both bone is retained over the area of contact be- sides in PSS-MAE 108, on the left side in tween the cerebral hemispheres and the cer- 135, and on the right side of AMNH 21708, ebellum (®g. 19). There appears to be two revealing a V-shaped facet on the frontal that layers of bone here, which in light of the extends posteriorly beyond the level of the ontogeny of this region in some extant pla- fronto-parietal suture on the midline (®gs. centals (Zeller, 1983, 1987; Schrenk, 1989) 17, 18, 20). The parietal shows a strong con- could represent the interparietal overlain by vex expansion to form the roof of the brain- the parietals. However, in light of the exten- case (®gs. 17±20), the squamosal being re- sive damage to this portion of the skull in stricted to the lateral wall (®gs. 42, 44A, B). PSS-MAE 130, we refrain from including an A low but distinct sagittal crest runs the en- interparietal in our reconstruction (®g. 42). tire length of the parietals to the nuchal As observed by Gregory and Simpson (lambdoidal) crest. The sagittal crest is most (1926a), a narrow, complete zygoma, strong- pronounced posteriorly in AMNH 21708 ly arched laterally, is preserved on the left (®g. 17), but not in PSS-MAE 108 (®g. 18) side of the holotype of Zalambdalestes lechei and 135 (®g. 20). The nuchal crest is very AMNH 21708 (®gs. 17, 22, 32). Sutures de- pronounced in AMNH 21708 (®g. 17), but limit its contributing elements (®g. 4A; Van poorly preserved in the MAE specimens Valen, 1964: ®g. 2). A similar shaped, com- (®gs. 18, 20). There is an indication of a faint plete zygoma is also preserved bilaterally in rugosity or sculpturing on the dorsal and lat- ZPAL MgM-I/16 (®g. 4B; Kielan-Jaworow- eral surfaces of the parietal in the area of ska, 1969a, 1984a) and on the left side in attachment for the temporalis muscles. A su- PSS-MAE 130 (®gs. 19, 26, 35). The jugal ture between the parietals and an interparietal is the principal element of the anterior zy- bone in the posterior skull roof is not dis- goma (also contributing to the lower third of 60 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 2004 WIBLE ET AL.: ZALAMBDALESTES 61 the orbital rim) and the squamosal of the pos- glenoid fossa for articulation of the lower terior zygoma. In fact, in lateral view in PSS- jaw on the ventral surface of the posterior MAE 130, the jugal is the only arch element root of the zygoma is broad and shallow visible, except at the rear where it is overlain (®gs. 35, 37A, B). In lateral view in PSS- by the squamosal (®g. 26). This is also the MAE 108 and 130 and in AMNH 21708, the overall pattern in AMNH 21708 (®g. 22), al- ventral aspect of the squamosal behind the though Van Valen (1964: ®g. 2) incorrectly glenoid fossa has three well-developed, ven- reconstructed a prominent zygomatic process trally directed processes: from front to back of the maxilla (®g. 4A). On the face in PSS- the postglenoid process (which continues for- MAE 130, the jugal has a broad connection ward as the entoglenoid process), the post- via an arcuate suture with the lacrimal anter- tympanic crest (see Basicranium and Audi- odorsally and the short zygomatic process of tory Region), and the slightly longer, stouter the maxilla anteriorly and ventrally (®g. 26). posttympanic process (®gs. 22, 23, 27). The Opposite the M3, the jugal narrows dorso- posterior aspect of the posttympanic process ventrally to a considerable extent and then lies on the occiput, completing the nuchal tapers to a small prong that occupies a facet crest, and is formed chie¯y by the mastoid on the ventral surface of the squamosal at the portion of the petrosal bone in the form of lateral edge of (but not within) the glenoid the paroccipital process, based on the left fossa (®gs. 35, 36, 37A, B). Running the side of PSS-MAE 130 (®gs. 37A, B, 40). Ex- length of the lateral surface of the jugal is a tending between the postglenoid and post- low ridge for the attachment of the masseter; tympanic processes is the medially curved it begins opposite M1, at the anteroventral suprameatal bridge, arching over the external corner of the bone, and arches posterodor- acoustic meatus (®gs. 22, 26, 37C). This sally such that it ultimately achieves the dor- thick bridge in part comprises two horizontal sal border of the jugal near the glenoid (®gs. parallel ridges, separated by a depression. 26, 27). On the medial surface of the zygo- Located within this depression is a very large ma, the jugal anteriorly is strongly furcate, suprameatal foramen on the left side of PSS- with the dorsal process longer and broader MAE 108 (®g. 23) and 130 (®g. 26), and than the ventral process. Also visible on the AMNH 21708 (®g. 22), as also occurs in lep- medial surface is a deep facet occupied by tictids (®g. 53), didelphid marsupials, and the anterior end of the zygomatic process of certain xenarthrans and primates (see Nova- the squamosal, which has been displaced cek, 1986a: table 3, character 41). Two su- somewhat posteriorly. This facet is opposite prameatal foramina are present in Ukhaath- the ethmoidal foramen in the orbit. The zy- erium (personal obs.) and only one in Ken- gomatic process of the squamosal in AMNH nalestes (®g. 51E), Asioryctes (®g. 51D), and 21708 (®g. 22) is considerably longer than Daulestes (®g. 51F), which was called a in PSS-MAE 130 (®g. 26), reaching to the subsquamosal foramen by Kielan-Jaworow- level of the last upper molar. ska (1981) and McKenna et al. (2000); we The squamosal contribution to the poste- restrict the latter term for foramina dorsal to rior zygoma is notable in showing distinct, the suprameatal bridge. A well-developed, horizontal ¯aring above the region of the ovoid subsquamosal foramen lies in the tem- glenoid fossa (®g. 19). Concomitantly, the poral fossa above the suprameatal foramen

← Fig. 29. Stereophotograph of the skull of Zalambdalestes lechei PSS-MAE 130 in right lateral view, with accompanying line drawing. Gray pattern represents matrix. Abbreviations: as, alisphenoid; C, upper canine; ecpc, ectopterygoid crest; ef, ethmoidal foramen; egp, entoglenoid process; fo, foramen ovale; fr, frontal; fro, foramen rotundum; I3, upper third incisor; M1, upper ®rst molar; M2, upper second molar; M3, upper third molar; mx, maxilla; na, nasal; oc, occipital condyle; opf, optic foramen; os, orbitosphenoid; otg, orbitotemporal canal; P2, upper second premolar; P3, upper third premolar; P4, upper fourth premolar; p, para¯occulus; pmxf, premaxilla facet on maxilla; pt, pterygoid; sof, superior orbital ®ssure; sq, squamosal. 62 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 30. Stereophotograph of the skull of Zalambdalestes lechei PSS-MAE 135 in left lateral view, with accompanying line drawing. Gray pattern represents matrix; parallel lines are damaged surfaces. Abbreviations: con, (mandibular) condyle; fr, frontal; hhu, head of humerus; ju, jugal; lac, lacrimal; mx, maxilla; na, nasal; pa, parietal; pop, postor bital process; sq, squamosal; tl, temporal line; tlc, translacrimal canal. 2004 WIBLE ET AL.: ZALAMBDALESTES 63

Fig. 31. Stereophotograph of the skull of cf. Zalambdalestes sp. PSS-MAE 129 in right lateral view, with accompanying line drawing. Gray pattern represents matrix; parallel lines are damaged surfaces. Abbreviations: C, upper canine; con, (mandibular) condyle; cor, coronoid process; fr, frontal; I2, upper second incisor; ma, mandible; maf, masseteric fossa; mx, maxilla; na, nasal; P1, upper ®rst premolar; P2, upper second premolar; P3, upper third premolar; p2, lower second premolar; p3, lower third premolar; pe, petrosal; pmx, premaxilla. 64 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 32. Stereophotograph of the skull of Zalambdalestes lechei AMNH 21708 in ventral view, with accompanying line drawing. Gray pattern represents matrix; parallel lines are damaged surfaces. Ab- breviations: C, upper canine (broken); con, (mandibular) condyle; egp, entoglenoid process; I2, upper second incisor (broken); ju, jugal; M1, upper ®rst molar; M2, upper second molar; M3, upper third molar; mapf, major palatine foramen; mx, maxilla; P2a, upper second premolar alveolus; P3, upper third premolar; P4, upper fourth premolar; pgf, postglenoid foramen; pgp, postglenoid process; pmx, premaxilla; ppr/ptp, paroccipital process/posttympanic process; sq, squamosal.

and bridge in PSS-MAE 108 (®g. 18) and on ramen cannot be con®rmed in the remaining the left side of PSS-MAE 130 (®gs. 19, 26) MAE or CAE specimens as this part of the and AMNH 21708 (®gs. 17, 22) and is vis- temporal fossa is not suf®ciently preserved ible in the stereophotograph of ZPAL MgM- or exposed. More dorsally, the squamosal I/16 (Kielan-Jaworowska, 1984b: pl. 30, ®g. contacts the parietal along a roughly hori- 1a). The incidence of the subsquamosal fo- zontal suture, based on PSS-MAE 108 and 2004 WIBLE ET AL.: ZALAMBDALESTES 65

nium has been prepared, except immediately posterior to the choanae and near the jaw joints and left ectotympanic bone (®gs. 33, 34). In general, it is not as well preserved as that in PSS-MAE 130 (e.g., the sutures are not as clear), yet it provides some details not shown in the latter. For our description, we divide the basicranium into anterior and posterior parts. The anterior part or mesocra- nium includes the area between the choanae and the anterior extent of the ear region; the posterior part includes the remainder of the braincase ¯oor. The most prominent features of the me- socranium are the paired, triangular-shaped ento- and ectopterygoid crests (®gs. 33±35). For descriptive purposes, we divide the downward-trending entopterygoid crests into anterior and posterior halves, which exhibit different orientations and compositions from each other. The posterior half of the entopterygoid crest is formed entirely by the pterygoid bone and is essentially vertical, although its ventral end converges medially below the nasopharyngeal trough (®g. 35). The crest's anterior half also has a vertical component, but its ventral end is ¯ared laterally, at the same level as the back of the palate. Forming the medial surface of the vertical component are the pterygoid bone dorsally and the perpendicular plate of the Fig. 32. Continued. palatine bone ventrally. The pterygoid forms the lateral surface of the vertical component as well as the laterally ¯ared ventral end 135 and AMNH 21708 (®gs. 18, 23, 44A, (®gs. 43, 44B); the reconstruction by Kielan- B). As in the case of the dorsal exposure of Jaworowska (1984a: ®g. 1), which is based the parietal, there is some surface rugosity on on Barunlestes, shows the maxilla forming the temporal moiety of the squamosal. the latter (®g. 4D). BASICRANIUM AND AUDITORY REGION: The The major elements of the roof of the na- basicranium of Zalambdalestes lechei is es- sopharyngeal trough between the entoptery- sentially unknown in specimens from the goid crests in PSS-MAE 130 are the paired CAE or the Polish±Mongolian and Soviet± pterygoid bones (®g. 35). These elements Mongolian Expeditions; the exception is that contact each other on the midline throughout the basicranial surface of the squamosal is the bulk of their length, except anteriorly preserved, albeit poorly, in the type AMNH where they are separated by an unpaired os- 21708 (®g. 32). In the MAE collection, the si®cation (see below). The pterygoids can be basicranium, from the choanae to the occip- traced into the nasal cavity, where they con- ital condyles, has been prepared in PSS- tribute to the lateral roof; additional details MAE 130 and preserves exquisite morpho- of the composition of the roof anterior to the logical detail and most sutural relationships choanae are hidden by matrix. The posterior (®gs. 35±37). Consequently, this specimen extent of the pterygoids is well indicated by provides the bulk of the descriptions that fol- a roughly transverse suture between the back low. In PSS-MAE 108, most of the basicra- of the entopterygoid crest and the carotid fo- 66 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

TABLE 3 Cranial Measurements (mm) of Zalambdalestes

ramen (®gs. 35, 37A, B). In addition to the than the entopterygoids and, based on PSS- pterygoids, the anterior third of the nasopha- MAE 130, are formed chie¯y by the alisphe- ryngeal roof has what appears to be a nar- noid (®gs. 35, 37A, C). The pterygoid forms row, ¯at midline element, which tapers to a most of the anterior half of the medial sur- point posteriorly. This element has been dis- face of the ectopterygoid crest, with only a torted and does not lie ¯at on the skull base, thin exposure of alisphenoid along the lateral but we think it did in life. If this truly is a edge. The ectopterygoid crest was identi®ed midline element and not artifactually pro- as the pterygoid process of the basisphenoid duced, it must be the posterior end of the in Barunlestes by Kielan-Jaworowska and vomer. Unfortunately, we cannot con®rm this Tro®mov (1980) and in Zalambdalestes by by tracing this element into the nasal cavity Kielan-Jaworowska (1984a), but in extant because of poor preservation. Lateral to the mammals (e.g., Tupaia, Zeller, 1983) it possible vomer, the contribution of the pter- forms as part of the alisphenoid. The lateral ygoids to the nasopharyngeal roof is essen- surfaces of both the ento- and ectopterygoid tially ¯at. However, posterior to the possible crests in Z. lechei have well-developed fos- vomer, there is a low crest at the interptery- sae for the attachment of the medial and lat- goid suture that becomes more prominent eral pterygoid muscles, respectively (®gs. 26, posteriorly. This crest divides the posterior 29). part of the nasopharyngeal roof into two con- The skull base between the ectopterygoid cave channels. Causing some distortion in crests is formed by the pterygoids anteriorly the nasopharyngeal roof posterior to the pos- and the basisphenoid posteriorly (®gs. 35, sible vomer is a transverse crack through the 37A, C). The individual basicranial compo- braincase and skull base that amazingly nents of the sphenoidÐpresphenoid, basi- enough did not damage the underlying, del- sphenoid, and alisphenoidÐare not delimited icate entopterygoid crests. by sutures in PSS-MAE 108 or 130. These The obliquely trending ectopterygoid elements form a unity in the adult skull but crests are more posterolaterally positioned are treated here as separate entities that cor- 2004 WIBLE ET AL.: ZALAMBDALESTES 67 respond with similar structures in living among mammals is not well understood. mammals for which the individual ossi®ca- Among Recent forms, it is lacking in mono- tion centers are known. The most conspicu- tremes (Kuhn, 1971; Zeller, 1989) and has ous feature is a midline crest continuous with only been described in a handful of therians, that described above along the interpterygoid including pouch young Didelphis virginiana suture. This crest is preserved in PSS-MAE (Presley and Steel, 1978), prenatal Zaedyus 108 (®g. 33) and 130 (®g. 35), but it shows minutus (Reinbach, 1952, 1955), juvenile some differences. In the former it gradually Cynocephalus volans (ϭ Galeopithecus phi- decreases in height and in width at its dorsal lippinensis, Parker, 1885), and adult Camelus base, from front to back, with its posterior bactrianus (Starck, 1967). At least in the limit lying at a point opposite the carotid fo- opossum and colugo, the parasphenoid ap- ramina (®g. 33). In the latter, the crest appears to be only variably present, as the el- pears to have its deepest extension in front ement is not named in other comprehensive of the carotid foramina, with an abrupt edge studies of cranial ontogeny in these forms and a much lower crest continuing posteri- (e.g., Toeplitz, 1920; Henckel, 1929; Halbs- orly between the carotid foramina (®g. 35). guth, 1973). Until more is known about the Based on PSS-MAE 130, the crest lies at the occurrence of this enigmatic element among juncture of the pterygoids and basisphenoid extant therians, we cannot rule out its pres- (®gs. 35, 37A, C). Sutures clearly delimit it ence in Zalambdalestes. from the pterygoids, but because of poor Behind the troughs for the nasopharynx on preservation it is unclear whether it is con- the pterygoids, the basisphenoid has roughly tinuous with the basisphenoid posteriorly. the shape of a square in PSS-MAE 108 (®g. We think that this crest is either part of the 33) and 130 (®gs. 35, 37A, C). At the level basisphenoid or parasphenoid (see below). of the postglenoid process, the basisphenoid On either side of the midline crest, the pter- meets the basioccipital at a horizontal suture, ygoid shows a longitudinal trough for the na- which is wider in PSS-MAE 130 than in 108. sopharynx that is continuous anteriorly with Lateral to that suture, the basisphenoid con- that between the entopterygoid crests and tacts the petrosal at a suture that exhibits dif- that ends posteriorly just in front of the ca- ferences between the two specimens. In PSS- rotid foramina. The concavity of these MAE 108, the suture is oblique, but in 130 troughs accentuates the height of the midline it is straight (longitudinal) posteriorly, but crest. then bends laterally at the tip of the promon- The location and form of the midline crest torium's anterior pole (®g. 37A, C). Anterior is similar to that described by Kielan-Jawo- to the petrosal, the lateral edge of the basi- rowska and Tro®mov (1980) for Barunlestes, sphenoid runs forward (obliquely toward the except that the latter also has a distinct hook- midline in PSS-MAE 108 and straight in like process at its posterior end. These au- 130), forming the anteromedial border of the thors identi®ed the crest in Barunlestes as the elongate, narrow, elliptical piriform fenestra, median process of the presphenoid. We think the gap in the skull base between the petrosal that this term is not re¯ective of the condi- and sphenoid. At the anteriormost extent of tion in either Zalambdalestes or Barunlestes, the piriform fenestra, the basisphenoid arches as in both the crest is beneath parts of the laterally into the base of the ectopterygoid skull base that are in the position of the ba- crest of the alisphenoid, which forms the sisphenoid of extant mammals. Additionally, obliquely oriented, lateral border of the pir- the basisphenoid may not be the only bone iform fenestra. In front of the petrosal and of origin for this crest. A similar midline separated from that bone by a suture is a sliv- ridge in, for example, Morganucodon (Ker- er of bone that runs dorsomedially into the mack et al., 1981), the multituberculate piriform fenestra on both sides in PSS-MAE Lambdopsalis (Miao, 1988), and the proto- 130 (®g. 37A, B). Preliminary study of high- tribosphenidan Vincelestes (Rougier, 1993) resolution CT scans of PSS-MAE 130 re- has been identi®ed as the parasphenoid, veals that this process is continuous with the which is reported to be fused to the basi- posterior clinoid process at the posterolateral sphenoid. The history of the parasphenoid corner of the hypophyseal fossa and there- 68 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 33. Stereophotograph of the skull of Zalambdalestes lechei PSS-MAE 108 in ventral view, with accompanying line drawing. Gray pattern represents matrix. Abbreviations: an, (mandibular) angle; at, atlas; C, upper canine; cf, carotid foramen; con, (mandibular) condyle; ec, ectotympanic; ecpc, ectopterygoid crest; egp, entoglenoid process; enpc, entopterygoid crest; fr, frontal; hf, hypoglossal foramina; I1, upper ®rst incisor; I2, upper second incisor; i1, lower ®rst incisor; inf, incisive foramen; jf, jugular foramen; ju, jugal; M1, upper ®rst molar; ma, mandible; mx, maxilla; P1, upper ®rst premolar; P2, upper second premolar; P3, upper third premolar; P4, upper fourth premolar; pf/fo, piriform fenestra/ foramen ovale; pmx, premaxilla; ppr/ptp, paroccipital process/posttympanic process; pr, promontorium; tp, tympanic process of Kielan-Jaworowska (1981). fore is part of the basisphenoid. There is no Positioned in the basisphenoid on either element like this in PSS-MAE 108 (®g. 33), side of the midline, opposite the anterior ex- but that is likely a product of inferior pres- tent of the piriform fenestrae, are oval carotid ervation. Kielan-Jaworowska and Tro®mov foramina for the passage of the internal ca- (1980: ®g. 2) illustrated a very similar struc- rotid arteries into the Circle of Willis at the ture on the right basicranium of Barunlestes base of the brain (®gs. 33, 35, 37A, B). Lead- (PIN 3142±701) (see ®g. 4D). ing into the carotid foramina from behind are 2004 WIBLE ET AL.: ZALAMBDALESTES 69

above (®gs. 43, 44A, B). Sutures delimiting the alisphenoid from the more dorsolaterally situated squamosal anteromedial to the glenoid fossa are visible on both sides of PSS- MAE 108 and on the left of PSS-MAE 130 (®g. 35); the alisphenoid approaches but does not contribute to the glenoid. Extending posterolaterally from the base of the ectopterygoid crest in PSS-MAE 130 is a delicate process on the alisphenoid (®g. 37A, B). On the medial side of this process is the piriform fenestra and on the lateral side is the foramen ovale for the mandibular division of the tri-

geminal nerve (V3). In PSS-MAE 108, this process is wholly missing (presumably broken), and the piriform fenestra and foramen ovale are con¯uent (®g. 33). The foramen ovale and piriform fenestra are separated by the base of the ectopterygoid crest in Barun- lestes (Kielan-Jaworowska and Tro®mov, 1980: ®g. 2). In PSS-MAE 130, the narrow, obliquely oriented foramen ovale lies on the lateral wall of the braincase (®gs. 26, 29), and the bulk of the aperture is enclosed by the alisphenoid; the squamosal and petrosal form only the posteriormost border (®g. 37A±C). Immediately anteroventral to the foramen ovale, in the posterior base of the left ectopterygoid crest of the alisphenoid of PSS- MAE 130, there is a small aperture (®g. 37A, B), which in their data matrix Rougier et al. (1998) interpreted as the posterior entrance Fig. 33. Continued. to an alisphenoid canal, previously unreport- ed in Zalambdalestes or Barunlestes. In extant mammals, such an aperture transmits the shallow but distinct, elongate sulci in the ba- ramus infraorbitalis of the stapedial artery or sisphenoid (®g. 37A). These carotid sulci be- maxillary artery, usually a substantial vessel, gin posteriorly at the basisphenoid-petrosal forward to the orbit (Wible, 1987). Addition- suture, anteromedial to the main bulge of the al preparation has revealed that this aperture promontorium. In the interval between the does indeed lead into a short canal that opens carotid foramina, carotid sulci, and basioc- at a small, anteriorly directed foramen on the cipital, the basisphenoid is essentially ¯at in dorsolateral surface of ectopterygoid crest. PSS-MAE 108 (®g. 33). However, in PSS- From this foramen, a short groove runs an- MAE 130, it bears three rounded, longitudi- teroventrally into another small foramen dinal prominences: one on the midline, repre- rected medially into the substance of the ec- senting the posterior continuation of the me- topterygoid crest. To verify this canal, the socranial midline crest, and two on either specimen's right ectopterygoid crest was also side, forming the medial borders of the ca- cleaned of matrix. A small aperture was rotid sulci (®gs. 35, 37A). found in the posterior base of the ectopter- The alisphenoid includes the ectoptery- ygoid crest, but it was situated more dorso- goid crest and, dorsolateral to it, the contri- laterally than on the left side. Moreover, no bution to the orbitotemporal fossa described egress for this foramen on the dorsolateral 70 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 34. Stereophotographs of the basicranium of Zalambdalestes lechei PSS-MAE 108 in ventral (A) and oblique (B) views. The latter shows the left ectotympanic bone with its ®ngerlike posterior crus and its laterally expanded anterior crus. 2004 WIBLE ET AL.: ZALAMBDALESTES 71 surface of the right ectopterygoid crest was ward the jugular foramen. Halfway between found. In PSS-MAE 108, the right ectopter- the basisphenoid-basioccipital suture and the ygoid crest was prepared and showed no ap- U-shaped odontoid notch, on either side of ertures whatsoever, either in the posterodor- the midline in PSS-MAE 130, are large, oval sal base or on the dorsolateral surface (®g. fossae, slightly obliquely oriented (®gs. 35, 33); the left side was not cleaned of matrix 37A, B). These fossae, presumably for well- to provide a buttress for the delicate ectotym- developed rectus capitis muscles, are largely panic bone (see below). We now think that in the basioccipital, but their anterolateral the small, variably present canal through the part is in the posteromedial aspect of the left ectopterygoid crest in PSS-MAE 130 is promontorium of the petrosal and their pos- not an alisphenoid canal; that is, its principal terolateral part, by the jugular foramen, is in occupant was not the ramus infraorbitalis or the bone we identify as the exoccipital. In maxillary artery. Similar, small, variably pre- PSS-MAE 108 (®g. 33), these fossae are present canals or foramina through the ectopter- sent in the basioccipital but are not as well ygoid crest transmitting branches of the man- developed as in PSS-MAE 130. dibular nerve have been described in some The most conspicuous feature on the ex- extant forms, including leporids (Frick and occipital is the large, prominent condyle (®g. Heckmann, 1955) and various primates 43). Our descriptions of the condyle are (Hershkovitz, 1977). In fact, in light of its based on PSS-MAE 130 (®gs. 35, 37A, 40), position, the canal in PSS-MAE 130 likely because in 108 the condyle is partially ob- transmitted nerves and/or vessels to the me- scured by the articulated cervical vertebrae. dial pterygoid muscle, as do similar struc- The extensive articular surface on the con- tures in some cercopithecoids (Hershkovitz, dyle can be divided into two ovoid lobes: (1) 1977). Also, as discussed in the Vascular Re- a larger posterolateral one, also visible on the construction, a more plausible route for the occiput, forming the ventrolateral margin of well-developed ramus infraorbitalis or max- the foramen magnum (®g. 40); and (2) a illary artery already exists in Zalambdales- smaller anteromedial one, largely bordering tes. the odontoid notch but not continuous across Posterior to the basisphenoid is the basi- the midline (®gs. 35, 37A, B). The axes of occipital, and posterolateral to that are the these two lobes are not in the same plane or paired exoccipitals (®g. 43). The basioccipital and exoccipital bones are not delimited direction; the former is more dorsal and is by sutures in PSS-MAE 108 (®g. 33) and oriented from anterolateral to posteromedial, 130 (®gs. 35, 37A), and we describe them whereas the latter is the reverse. Preserved based on their usual positions in extant mam- on both sides of PSS-MAE 108, between the mals. The basioccipital typically stretches posterolateral lobe of the condyle and the from the basisphenoid suture to the odontoid fossa for the rectus capitis, are two subequal notch in the anterior part of the foramen hypoglossal foramina (®g. 33): the slightly magnum, whereas the exoccipitals form the larger anterior one situated immediately in bulk of the condyles, contribute to the clo- front of the posterior one. The left side of sure of the jugular foramina, and enclose the PSS-MAE 130 also preserves the hypoglos- hypoglossal nerves (Starck, 1967). In Za- sal foramina (®g. 37A, B), but its anterior lambdalestes, the anterior part of the basi- opening is actually divided into two subequal occipital is roughly square-shaped and fea- apertures. Anterolateral to the hypoglossal tureless; its sutures with the petrosals follow foramina is the subcircular jugular foramen, a gentle curve in a nearly sagittal plane (®gs. which is subequal to the round window on 33, 35, 37A, C). This part of the basioccipital the back of the promontorium of the petrosal. appears to be wider in PSS-MAE 130 (®g. The exoccipital forms the medial border of 35) than in 108 (®g. 33), but the right petro- the jugular foramen. The posterior border of sal in the latter has been displaced somewhat the jugular foramen is formed by a narrow, medially. Posteriorly, the basioccipital more triangular process, the bulk of which is on than doubles in width as the suture with the the petrosal; the exoccipital contributes the petrosal runs obliquely, posterolaterally to- medial one-third and this small prominence 72 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 35. Stereophotograph of the skull of Zalambdalestes lechei PSS-MAE 130 in ventral view, with accompanying line drawing. Gray pattern represents matrix. Abbreviations: art, artifact; bo, basioccipital; C, upper canine; ecpc, ectopterygoid crest; ef, ethmoidal foramen; enpc, entopterygoid crest; gf, glenoid fossa; I1a, upper ®rst incisor alveolus; I2a, upper second incisor alveolus; iof, infraorbital foramen; inf, incisive foramen; ju, jugal; M1, upper ®rst molar; M2, upper second molar; M3, upper third molar; mpf, minor palatine foramina; mapf, major palatime foramina; mx, maxilla; oc, occipital condyle; P2, upper second premolar; P3, upper third premolar; P4, upper fourth premolar; pf, piriform fenestra; pms, palatomaxillary suture; pmx, premaxilla; ppt, postpalatine torus; pr, promontorium; pt, pterygoid; sq, squamosal; vo, vomer. represents a paracondylar process of the ex- bones, the principal elements of the posterior occipital (sensu Evans, 1993). basicranium (®g. 43). PSS-MAE 130 pre- Lateral to the basisphenoid, basioccipital, serves exquisite detail of the petrosal (®gs. and exoccipitals are the paired petrosal 35, 37), whereas this bone is not so well pre- 2004 WIBLE ET AL.: ZALAMBDALESTES 73

drop-shaped prominence (®g. 37A, C). The promontorium represents the actual housing for the cochlear duct, which Kielan-Jawo- rowska (1984b) reported to be one whorl based on an endocast of ZPAL MgM-I/16 (but see below). Flat ¯anges extend medially, anteriorly, and anterolaterally from the promontorium, with that extending anteriorly being the broadest (®g. 37A). A small, faint depression on the anterolateral ¯ange in PSS- MAE 130 likely housed the attachment of the tensor tympani muscle. Two apertures open into the back of the promontorium: the fenestra cochleae (round window) posteriorly and the fenestra vestibuli (oval window) posterolaterally. The fenestra cochleae faces posterolaterally and is shaped like a half-circle with its dorsal margin straight. The borders of the anteroventrolaterally facing, elliptical fenestra vestibuli are well preserved on the left side of PSS-MAE 130 and yield a stapedial ratio (length/width; see Segall, 1970) of 2.3. The contours of the rim of the fenestra vestibuli are ¯at anteriorly, broadly concave dorsolaterally, with a raised crest posteriorly, and with a narrow concavity ven- tromedially. The last is in the posterior third of the ventromedial border and is continuous with a well-developed groove on the back of the promontorium that extends to just in front of the fenestra cochleae. This groove along with the concavity in the dorsolateral border of the fenestra vestibuli provided passage for Fig. 35. Continued. the stapedial artery. In light of the position of the groove, the stapedial artery must have penetrated the intracrural (obturator) foramen served in PSS-MAE 108 (®gs. 33, 34). In of the stapes, as in extant placentals preserv- extant mammals, the petrosal can be divided ing the artery (Novacek and Wyss, 1986b; into two parts: the pars cochlearis, antero- Wible, 1987; Gaudin et al., 1996). A shallow ventrally placed and housing the cochlea, and stapedial groove is also preserved on both the pars canalicularis, posterodorsally placed sides of PSS-MAE 108. Neither specimen and housing the vestibule and semicircular has a transpromontorial sulcus for the inter- canals. In Zalambdalestes, the pars cochlear- nal carotid artery (see below) or a rostral is, the main feature of which is the promon- tympanic process for contact with a bullar torium, is a large, oval element, which com- element (®gs. 33, 37A). As mentioned above, prises the bulk of the petrosal visible in ven- the posteromedial aspect of the promonto- tral view (®g. 37A, C). The pars canalicularis rium in PSS-MAE 130 bears a fossa contin- lies posterior and lateral to the pars coch- uous with that for the rectus capitis on the learis in ventral view and forms the mastoid basioccipital and exoccipital (®g. 37A, B). exposure on the occiput (®gs. 37A, 40). This fossa is not evident on the promonto- Centrally located on the posterior half of rium in PSS-MAE 108 (®g. 33). the pars cochlearis is the promontorium of Anteromedial to the fenestra vestibuli on the petrosal, a low, obliquely oriented, tear- both sides of PSS-MAE 130 is a narrow, 74 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 36. Stereophotograph of the posterior part of the skull of Zalambdalestes lechei PSS-MAE 130 in ventral view. shallow, anterolaterally directed depression tery, because it is too small compared with (®g. 37A, B); a similar, but fainter depression the caliber of the carotid foramen, and a is found on the left side of PSS-MAE 108. well-developed carotid sulcus is present on On the right side of PSS-MAE 130, this de- the basisphenoid-petrosal suture. However, pression begins just in front of the medial because the anterior terminus of this depres- extent of the groove for the stapedial artery, sion is not near another groove, canal, or fo- whereas on the left the two appear continu- ramen, it may not have housed a neurovas- ous (®g. 37A, B). Laterally, this depression cular structure. Rather than a neural groove, ends abruptly posterior to the fossa for the this depression may have been a facet for the tensor tympani muscle, at the level of the articulation of the posterior crus of the ec- lateral lip of the fenestra vestibuli. If this de- totympanic (see below). pression housed a neurovascular structure, The aspects of the pars canalicularis visi- the most likely candidate is a tympanic ble in ventral view are best preserved in PSS- nerve, which follows a similar course in MAE 130 (®g. 37A). Behind the promonto- some extant placentals (MacPhee, 1981; rium are two depressions, which are bordered Evans, 1993). This depression did not con- posteriorly by a broad, low-lying, continuous tain a transpromotorial internal carotid ar- wall with two prominences situated roughly 2004 WIBLE ET AL.: ZALAMBDALESTES 75 behind the two depressions. The medial of ly, and is formed chie¯y by squamosal, with the two depressions lies immediately behind the petrosal comprising its posterior base, the fenestra cochleae. It is the cochlear fos- taken from the left side of PSS-MAE 130. sula (®g. 37B), which housed a diverticulum The squamosal's portion of this prominence of the cavum tympani, the air-®lled sac oc- is equivalent to what usually (e.g., Novacek, cupying the middle-ear space. The square- 1986a) is referred to as the posttympanic pro- shaped cochlear fossula is fairly smooth and cess of the squamosal, and we follow this ¯at, although it slopes ventrally from front to terminology here. The petrosal's contribution back, forming a small pocket above its pos- to the base of this process is equivalent in terior wall. Bordering the cochlear fossula position to what Rougier et al. (1992) called medially is the jugular foramen. The promi- the paroccipital process in the prototribo- nence behind the cochlear fossula is the tri- sphenidan Vincelestes or to what MacPhee angular process on the petrosal and exoccip- (1981) called the lateral section of the caudal ital mentioned above as forming the posterior tympanic process of the petrosal in various wall of the jugular foramen. Well preserved extant placentals. We follow the former ter- in PSS-MAE 108, the triangular process is minology for the petrosal base to re¯ect the directed anteroventrally, ending at the same homology of the process in Zalambdalestes level as the ventralmost extent of the prom- with that in more basal taxa. We use the term ontorium (®gs. 33, 37C). The triangular pro- caudal tympanic process of the petrosal sen- cess is equivalent in position to what Kielan- su Wible (1990) for the entire wall posterior Jaworowska (1981) called the tympanic pro- to the facial sulcus, stapedius fossa, cochlear cess on the petrosal in the asioryctithere Ken- fossula, and jugular foramen, medial to the nalestes or to what MacPhee (1981) called paroccipital process. Using this terminology, the medial section of the caudal tympanic the tympanic process behind the cochlear process of the petrosal in various extant pla- fossula is a prominence on the caudal tym- centals. We follow Kielan-Jaworowska in panic process. calling this the tympanic process here, but Immediately anteromedial to the paroccip- note that the condition in Zalambdalestes dif- ital process on the left sides of PSS-MAE fers from that in Kennalestes because of the 108 and 130 (®g. 37A, B) is the stylomastoid contribution from the exoccipital. The lateral notch, by which the facial nerve (VII) exited border of the cochlear fossula is formed by the middle-ear space. As evident from the a thin, low-lying lamina of bone that repre- latter specimen, the stylomastoid notch is in sents the posterior continuation of the broad both the squamosal and petrosal, with the crista interfenestralis, which separates the fe- squamosal underlying the petrosal. Forming nestrae vestibuli and cochleae on the back of the anteromedial margin of the stylomastoid the pars cochlearis (®g. 37B). Posteriorly, notch on the left side of PSS-MAE 130 is a this thin extension of the crista interfenes- posteromedially directed process on the pe- tralis abuts the lateral aspect of the tympanic trosal. This is the tympanohyal (®g. 37B), process. after the stapes the most proximal ossi®ca- The lateral of the two depressions, lying tion in Reichert's cartilage, the cartilage of immediately behind the fenestra vestibuli, is the second branchial arch. This ®ngerlike much larger and deeper than the cochlear process is expanded at its tip, which bears a fossula, from which it is separated by the thin posteromedially and ventrally directed facet crista interfenestralis. The medial two-thirds for the articulation of the stylohyal, the next of this ovoid depression is the fossa for the distal ossi®cation in the hyoid apparatus, stapedius muscle; the lateral one-third is the which is not preserved. Extending anteriorly sulcus for the facial nerve leading to the sty- from the tympanohyal is a low-lying ridge, lomastoid notch (®g. 37B). As with the tym- the crista parotica (®g. 37B), which marks panic process, the prominence in the postero- the point of embryonic articulation of Reich- lateral wall of the stapedius fossa and facial ert's cartilage and the pars canalicularis in sulcus is triangular and formed by two ele- extant mammals (De Beer, 1937; Starck, ments. However, it is much larger than the 1967). The crista parotica in PSS-MAE 130 tympanic process, projecting farther ventral- forms a border between two structures (®g. 76 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

37B). Medially, between the crista parotica squamosal and is subequal in size to the fe- and the lateral rim of the fenestra vestibuli is nestra vestibuli. Kielan-Jaworowska and Tro- the fairly broad and deep facial sulcus, which ®mov (1980) identi®ed a similar foramen in transmitted the facial nerve from the facial Barunlestes as the apertura externa canalis foramen in front to the stylomastoid notch facialis, but we have already identi®ed a fa- behind. The facial foramen lies opposite the cial foramen in a more appropriate position anterior rim of the fenestra vestibuli (®g. in PSS-MAE 130, that is, con¯uent with the 37B). Lateral and anterior to the crista par- facial sulcus. We think this second, more an- otica is a much larger, shallower, obliquely terolateral aperture in PSS-MAE 130 is more oriented depression in the tympanic roof, likely to have transmitted the ramus superior which is formed by the part of the pars can- of the stapedial artery (®g. 37B, D; see be- alicularis called the tegmen tympani (®g. low). 37B; De Beer, 1937; MacPhee, 1981; Wible, Extending anteroventromedially from the 1992). This ovoid depression is the epitym- epitympanic recess is a narrow process that panic recess (®g. 37B), which housed the represents the rostral continuation of the teg- mallear-incudal articulation. The posterolat- men tympani (®g. 37B). Best preserved on eral part of the epitympanic recess is ¯oored the left side of PSS-MAE 130, the tegmen by the squamosal and the anteromedial part tympani tapers to a rostral tip, which contacts is open on the skull base. Just lateral to the a narrow process of the alisphenoid that ex- crista parotica is a small, distinct pocket con- tends posterolaterally from the base of the tinuous with the epitympanic recess, the fos- ectopterygoid crest, behind the foramen sa incudis (®g. 37B), which housed the crus ovale for the mandibular nerve. The ventral breve of the incus. The fossa incudis is al- surface of the tegmen tympani bears a dis- most entirely in the petrosal, with the squa- tinct groove, which leads forward from the mosal contributing only a small part of its foramen of the ramus superior. From the ori- lateral wall. Anterolateral to the fossa incu- entation of this groove, it appears that its dis, in the anterolateral corner of the part of principal occupant was directed toward the the epitympanic recess ¯oored by the squa- piriform fenestra. Similarly situated grooves mosal, is a laterally directed, oval foramen. are called the groove for the ramus inferior This aperture lies between the petrosal and of the stapedial artery (e.g., Vincelestes,

→ Fig. 37. The left ear region of Zalambdalestes lechei PSS-MAE 130 in ventral view (A) with accompanying line drawings (B, C, and D). Pattern represents matrix. In panel B, parallel lines represent the broken tympanic process, which is reconstructed with dashed lines; stippled areas are facets; and fossa incudis, crista parotica, and postglenoid foramen, which are hidden by bone, are indicated by dashed lines. In panel C, the ectotympanic bone known from PSS-MAE 108 is reconstructed. In panel D, the major arteries and veins are reconstructed. Abbreviations: ac, anterior crus of ectotympanic; adm, arteria diploeÈtica magna; as, alisphenoid; bo, basioccipital; bs, basisphenoid; cca, common carotid artery; cf, carotid foramen; ci, crista interfenestralis; cof, cochlear fossula; cp, crista parotica; eam, external acoustic meatus; ec, ectotympanic; ecf, ectotympanic facet; ecpc, ectopterygoid process; egp, entoglenoid process; eo, exoccipital; er, epitympanic recess; evpgf, emissary vein of postglenoid foramen; ®, fossa incudis; fo, foramen ovale; frc, fossa for rectus capitis muscle; frs, foramen for ramus superior; fv, fenestra vestibuli; gf, glenoid fossa; gsa, groove for stapedial artery; hf, hypoglossal foramina; ica, internal carotid artery; ips, inferior petrosal sinus; jf, jugular foramen; ju, jugal; on, odontoid notch; pc, posterior crus of ectotympanic; pcf, facet for posterior crus; pcp, posterior clinoid process; pf, piriform fenestra; pgf, postglenoid foramen; pgp, postglenoid process; ppr, paroccipital process; pr, promontorium; ps?, parasphenoid?; pt, pterygoid; ptc, posttympanic crest; ptp, posttympanic process; ri, ramus inferior; rio, ramus infraorbitalis; rm, ramus mandibularis; rme, recessus meatus; rs, ramus superior; sa, stapedial artery; sf, fossa for stapedius muscle; smn, stylomastoid notch; sq, squamosal; th, tympanohyal; tp, tympanic process of Kielan-Jaworowska (1981); tt, tegmen tympani; ttf, fossa for tensor tympani muscle; V3br, branch of mandibular division of trigeminal nerve; vv, vertebral vein. 2004 WIBLE ET AL.: ZALAMBDALESTES 77 78 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 37. Continued.

Rougier et al., 1992) or the glaserian ®ssure chorda tympani nerve, although the ramus (e.g., Leptictis, Novacek, 1986a). We use the inferior is also sometimes present (Klaauw, former term here to re¯ect the homology of 1931; MacPhee, 1981). As preserved in PSS- the sulcus in Zalambdalestes with more basal MAE 130, the tip of the tegmen tympani taxa and because we think the primary oc- contributes to the posterior border of the fo- cupant of this sulcus to be the ramus inferior ramen ovale (®g. 37B). Dorsal to the anterior (see below). The primary occupant of the tip of the tegmen tympani is an aperture in glaserian ®ssure in extant placentals is the the petrosal, the hiatus Fallopii (®g. 37B), 2004 WIBLE ET AL.: ZALAMBDALESTES 79

Fig. 38. Stereophotograph of the skull of Zalambdalestes lechei PSS-MAE 135 in ventral view. which transmitted the greater petrosal nerve, side of one specimen of Barunlestes (PIN a branch of the facial nerve. The hiatus does 3142±701), Kielan-Jaworowska and Tro®- not open endocranially but just below the mov (1980) described a small foramen (for level of the piriform fenestra. their ramus meningea of the stapedial artery) Anteromedial to the tip of the tegmen tym- in the anterior ¯ange of the pars cochlearis. pani is the obliquely oriented, elongate, nar- We think this to be an artifact, as no such row piriform fenestra (®g. 37B). The borders aperture is present in Zalambdalestes or any of the piriform fenestra are as follows: pos- other eutherian known to us. teriorly, the tegmen tympani; posteromedi- The squamosal forms the lateral aspect of ally, the anterior and anterolateral ¯ange of the basicranium (®g. 37A, C). At the antero- the pars cochlearis; anteromedially and an- lateral margin of the squamosal is the zygo- teriorly, the basisphenoid; and laterally, the matic process, the posterior edge of which is alisphenoid. Kielan-Jaworowska and Tro®- at the level of the basisphenoid-basioccipital mov (1980) identi®ed the anterior part of a suture, well anterior to the fenestra vestibuli. similar gap in the skull base in Barunlestes The zygomatic process bears almost the en- as the foramen for the stapedial artery. How- tire articular surface of the glenoid fossa, the ever, we think that this is the piriform fenes- bulk of which lies external to the molars tra, which in both Zalambdalestes and Ba- (®gs. 32, 33, 35). This was also noted by runlestes transmitted the ramus inferior of Gregory and Simpson (1926a) based on the the stapedial artery into the cranial cavity en holotype of Zalambdalestes lechei (AMNH route to the orbit (see below). On the right 21708), but Kielan-Jaworowska (1984a) re- 80 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 39. Stereophotograph of the skull of cf. Zalambdalestes sp. PSS-MAE 129 in ventral view, with accompanying line drawing. Gray pattern represents matrix; parallel lines are badly worn teeth. Abbreviations: con, (mandibular) condyle; i1can, canal (broken) for root of lower ®rst incisor; I2, upper second incisor; M1, upper ®rst molar; M2, upper second molar; M3, upper third molar; ma, mandible; P2, upper second premolar; P3, upper third premolar; P4, upper fourth premolar; pe, petrosal. stored the glenoid more medially, reaching glenoid; the posterolateral aspect has no rim nearly to the foramen ovale on the lateral and is slightly angled posterodorsally (®g. braincase wall (®g. 4D). The glenoid is a 37A). A prominent, thin crest, continuous large, shallow, horizontally arranged, oval but slightly lower than the postglenoid pro- depression, more transverse than anteropos- cess, curves anteromedially from the post- teriorly elongate (®g. 37A, B). A prominent glenoid, ending abruptly at the posterolateral but thin postglenoid process is preserved on corner of the foramen ovale (®g. 37A). As both sides of PSS-MAE 108 (®gs. 23, 33) shown on the left side of PSS-MAE 130, this and on the left side of 130 (®gs. 26, 37A, crest also comes to a point, but it does not C). The postglenoid process comes to a point project as far ventrally as that on the post- that projects ventrally to the same level as glenoid process; the apex is roughly halfway the posttympanic process of the squamosal between that on the postglenoid process and (®gs. 22, 26). As noted by Kielan-Jawo- the foramen ovale. Gregory and Simpson rowska (1984a), the postglenoid process bor- (1926a) applied the term entoglenoid process ders only the posteromedial aspect of the for the entire continuous crest stretching 2004 WIBLE ET AL.: ZALAMBDALESTES 81

bears an anteromedially directed facet, demarcated posteriorly by a low vertical crest. Based on the left side of PSS-MAE 108, the facet articulated with the anterior crus of the ectotympanic bone (see below). At the posteromedial corner of the glenoid fossa in PSS-MAE 130 (®g. 37B) and the right side of PSS-MAE 108, just in front of the entoglenoid and postglenoid processes, is an obliquely oriented, slitlike postglenoid foramen. This foramen is also preserved on the left side of the holotype of Zalambdalestes lechei (AMNH 21708), although it was not previously recognized (®g. 32). The postglenoid (retroarticular) foramen is the point of exit for the major drainage of the transverse sinus in extant therians (Wible, 1990). Typically, this aperture lies behind the postglenoid process (Novacek, 1986a), but there are exceptions (e.g., Camelus dromedarius, Smuts and Bezuidenhout, 1987) in which it lies anterior to the process as in PSS-MAE 130 and AMNH 21708. Kielan-Jaworowska and Tro®mov (1980) tentatively recognized the postglenoid foramen as posterior to the postglenoid process in Barunlestes, which is in contrast to the anterior position we found in Zalambdalestes. However, we found the foramen anterior to the postglenoid process in two specimens of Barunlestes,ZPAL MgM-I/77 and PIN 3142±701. Behind the glenoid region in PSS-MAE Fig. 39. Continued. 108 (®g. 33) and 130 (®gs. 35, 37A, C) is a broad, concave, posterodorsolaterally direct- from the posteromedial aspect of the glenoid ed trough in the squamosal for the external fossa to the foramen ovale, because of the acoustic meatus. The dorsal surface of this resemblance to the condition described by part of the squamosal forms the ¯oor for the Gregory (1910) in extant ``zalambdodont'' epitympanic recess, fossa incudis, and fora- insectivorans. In contrast, Kielan-Jaworow- men for the ramus superior described above. ska (1984a) labeled the entire complex the Forming the steep anterior wall of this U- postglenoid process. Rather than a single shaped trough are the entoglenoid and post- continuous crest, two separate entities are glenoid processes. The equally steep poste- present in some forms (e.g., Notharctus, Lep- rior wall, best seen on the left side of PSS- tictis), the posterolateral one by the glenoid MAE 130, can be divided into anteromedial fossa termed the postglenoid process and the and posterolateral segments separated by the anteromedial one the entoglenoid process stylomastoid notch. The posterolateral seg- (McDowell, 1958; MacPhee, 1981). We fol- ment is formed by the posttympanic process low this usage here, employing entoglenoid of the squamosal, the stout, ventrally direct- process for the lower crest extending anter- ed, triangular process, whose base is com- omedially from the postglenoid process. The posed of the petrosal bone (paroccipital pro- posteromedial surface of the entoglenoid cess in ®g. 37B). The anteromedial segment process in PSS-MAE 130 (®g. 37B) and on is formed by a sharp, anteromedially curving the right side of PSS-MAE 108 (®g. 33) crest on the squamosal, which approximates 82 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 the promontorium of the petrosal, antero- gies: the latter is very thin and delicate, ventral to the fenestra vestibuli (®g. 37B). whereas the former is expanded laterally to This crest underlies the base of the tympa- partially enclose the external acoustic mea- nohyal, partially obscuring that element in tus. ventral view. A similar crest was identi®ed The posterior crus of the ectotympanic is as the tympanohyal in Barunlestes by Kie- round in cross section and of uniform small lan-Jaworowska and Tro®mov (1980), but diameter throughout most of its length. It is this must be incorrect if the structure in ques- separated from the ventromedial aspect of tion is on the squamosal, as is clearly the the posttympanic crest of the squamosal by case in Zalambdalestes. We have not en- a few grains of sandstone matrix, but may countered a similar structure in the literature. have abutted this element during life. Where We propose the term posttympanic crest (®g. the posterior crus bends dorsally and then an- 37C) for this structure in Zalambdalestes teriorly to form one arm of the ``C'', it has (and presumably also Barunlestes). This term a slight kink in it that appears unnatural and re¯ects its position behind the tympanum, may represent some minor damage. The part while preserving its identity separate from of the posterior crus that extends forward the true posttympanic process. from the kink tapers slightly and has an ex- A notable feature preserved on the left tensive abutment on the promontorium me- side of PSS-MAE 108 is an ectotympanic dial to the fenestra vestibuli. It appears that (®gs. 33, 34B), which to date has not been this abutment is natural and would be within reported for any zalambdalestid. In preparing the depression on the promontorium de- the basicranium, the medial aspect of the scribed above. near vertical ectotympanic was encountered The anterior crus of the ectotympanic still ®rst. It presented the form of a simple, in- shows the ringlike form of the posterior one, complete ring. To preserve the delicate ec- although it is not quite as delicate. Moreover, totympanic, preparation of the left basicra- added to the ring on the anterior crus is a nium was halted. In the taxon-character ma- thin ¯ange of bone arching dorsolaterally. In trix in Rougier et al. (1998: character 142), the part of the anterior crus proximal to the we reported that the ectotympanic of Za- posterior crus, this ¯ange is not very pro- lambdalestes was ``ring-like'' based on what nounced. However, as the anterior crus was then known in PSS-MAE 108. After the curves dorsally, the ¯ange is expanded to publication of Rougier et al. (1998), some form the anterior face and roof of the part of additional preparation to the left basicranium the external acoustic meatus proximal to the of PSS-MAE 108 was done for illustrative tympanum. This ¯ange has an extensive con- purposes. From this, we discovered that the tact with the squamosal bone, on the facet on ectotympanic was not a simple element, but the medial aspect of the entoglenoid process that its anterior part was expanded laterally. described above and the troughlike surface Full preparation of the delicate ectotympanic behind. Because of the curve of the ¯ange, is not possible, but enough has now been unit forms a channel for the external meatus covered to allow the following description that is widest near the tympanum's attach- and reconstruction (®g. 37C). ment to the anterior crus and that narrows The ectotympanic is roughly C-shaped, al- laterally passing between the postglenoid though the posterior crus does not bend to process and posttympanic crest. This wider ®nish the ``C'' nearly to the same extent as part of the external meatus proximal to the the anterior one. This element is oriented tympanum is termed the recessus meatus vertically, essentially at a 90Њ angle to the acustici externi by Klaauw (1931), shortened skull base, below and medial to the trough to recessus meatus by McDowell (1958). The for the external acoustic meatus. This posi- tip of the anterior crus in PSS-MAE 108 re- tion likely approximates the orientation of peats the delicate form of the posterior crus; the ectotympanic in the living animal (see it approximates, but does not appear to be in below). The anterior and posterior crura, the direct contact with the sliver of alisphenoid anterior and posterior halves of the ectotym- between the piriform fenestra and foramen panic, exhibit strikingly different morpholo- ovale behind the ectopterygoid crest. 2004 WIBLE ET AL.: ZALAMBDALESTES 83

The ectotympanic preserved in PSS-MAE in both taxa is widest at its anteromedial 108 presents what appears to be an odd com- edge, with both crura rounded but with the bination of features. It is essentially vertical, posterior narrower than the anterior. This is with a simple posterior crus contacting the the shape that the ectotympanic has in Za- promontorium and an anterior crus expanded lambdalestes and Ukhaatherium. As reported laterally to partially enclose the recessus me- by Kielan-Jaworowska (1981), the two spec- atus and contacting the entoglenoid process imens of Asioryctes that preserve the ecto- of the squamosal. The vertical orientation is tympanic exhibit different degrees of incli- unusual compared to the more oblique posi- nation for that element. In ZPAL MgM-I/56, tion (45Њ angle) reported by Kielan-Jawo- it is roughly 45Њ to the horizontal, whereas rowska (1981, 1984c) for Asioryctes and in ZPAL MgM-I/98, it is almost vertical. Kennalestes (but see below), but in fact is Kielan-Jaworowska accepted the former as the condition found in most extant therians the natural position and treated the latter con- (Klaauw, 1931). The lack of expansion of the dition as the result of distortion. In light of posterior crus coupled with the lateral expan- the condition reported by us in Zalambdales- sion of the anterior is also found in the aard- tes and Ukhaatherium, we think it is likely vark and most lipotyphlans (personal obs.), that the almost vertical condition of the ec- and a walled recessus meatus occurs in many totympanic in ZPAL MgM-I/98 is the origi- forms with a bony meatus (Klaauw, 1931). nal position. Finally, contact between the anterior crus and An ectotympanic has also been identi®ed the entoglenoid process is found in some ten- for Daulestes by McKenna et al. (2000). recids and erinaceids (®g. 58; Klaauw, 1931; Found isolated in matrix at the rear of the MacPhee, 1981). In the reconstruction of the skull, this element is roughly U-shaped, with skull base in Asioryctes and Kennalestes by the transverse portion between the crura ex- Kielan-Jaworowska (1984c: ®g. 1), the an- panded, although not to the same extent re- terior crus approximates the entoglenoid pro- ported in Asioryctes by Kielan-Jaworowska cess (®g. 56), but it is unclear whether con- (1981). Whether this element is vertical or tact occurred. Such contact does occur in oblique in its orientation in Daulestes is Ukhaatherium, based on a facet on the ap- wholly unknown. It seems doubtful that the propriate face of the entoglenoid process in anterior crus contacted the entoglenoid pro- PSS-MAE 110 (personal obs.). cess, which as preserved is very small in Kielan-Jaworowska (1981) reported ecto- length and height. tympanics in two specimens of Asioryctes The vertically oriented ectotympanic with and one of Kennalestes. She (ibid.: 56) re- its laterally expanded anterior crus in PSS- constructed this element as ``large, forming MAE 108 is of interest with respect to the three-quarters of a ring, open in posterolat- possible condition of the auditory bulla. In eral-dorsal part, arranged obliquely (about no zalambdalestids are bony bullae pre- 45Њ) to the horizontal plane.'' Ukhaatherium served. There are no substantial processes of is reported to have a similar fusiform ecto- the basisphenoid, alisphenoid, petrosal, or tympanic bone (Novacek et al., 1997; Roug- squamosal that might indicate contributions ier et al., 1998). After the discovery of the to a bulla. Likewise, it is now evident that ectotympanic in Zalambdalestes, we revisit- the ectotympanic is not expanded medially ed the morphology of that bone in Ukhaa- and does not form a bullar component. therium (PSS-MAE 102) and found it to be Therefore, an ossi®ed bulla was either absent remarkably similar in shape, that is, ringlike in zalambdalestids or was formed by one or with a partial bony external acoustic meatus. more independent structures, generically re- We think that it also occupied a similar po- ferred to as entotympanics, a condition found sition on the skull base, that is, vertical and in leptictids (®g. 53), tupaiids, and a variety in contact with the entoglenoid process of the of other placental taxa (Butler, 1956; Mc- squamosal, based on PSS-MAE 110. We also Dowell, 1958; Novacek, 1977, 1986a; revisited the descriptions of the ectotympanic MacPhee, 1979). The presence of a partial in Asioryctes and Kennalestes by Kielan-Ja- bony external acoustic meatus in Zalamb- worowska (1981). She noted that this bone dalestes does not in and of itself require a 84 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 partial or complete bony auditory bulla. The to the nuchal crest. The suture between the aardvark (CM 57994) and Solenodon (CM exoccipital and supraoccipital is essentially 18069) have ectotympanics reminiscent of transverse, about halfway up the occiput, in- that in PSS-MAE 108, but with no substan- tersecting the foramen magnum near its dor- tial ossi®ed bulla. sal limit. Another small piece of bone 2 mm in The supraoccipital has a curved dorsal length was found in the vicinity of the left border on the nuchal crest and largely ectotympanic in PSS-MAE 108. This ¯at el- straight lateral and ventral borders, with one ement was found in contact with the ven- signi®cant exception. In the middle of its tralmost surface of the ectotympanic and ventral border, the supraoccipital has an up- from there projected ventrally. This element side-down, broad, U-shaped notch, which tapers to a blunt point at its ventral end and forms a cap on the otherwise ovoid foramen is widest at the opposite pole, which presents magnum. According to Kielan-Jaworowska a slightly oblique face. The surface in contact (1984a: 113), the supraoccipital in ZPAL with the ectotympanic is ¯at and the opposite MgM-I/16 ``is perforated by an unestablished surface is convex. This element is clearly not number of small foramina'', in which she re- in life position, but its identity is elusive. Of constructs a venous connection with the sig- the auditory ossicles, its morphology is most moid sinus. We are able to con®rm this ob- reminiscent of the manubrium of the malleus, servation in PSS-MAE 108, in which there which contacts the tympanum, but it appears are numerous small foramina, variable in size to be too massive for that. Perhaps it is a and number, near the nuchal crest and some- broken, more distant segment of the hyoid what ventral to it. Similar foramina occur in arch. Vincelestes (Rougier et al., 1992) and in the OCCIPUT: A partial occiput of Zalambda- dog, where they transmit a communication lestes (ZPAL MgM-I/16) has been described between the occipital emissary vein and the previously by Kielan-Jaworowska (1984a). transverse sinus (Evans, 1993). More complete occiputs are preserved in The bulk of the foramen magnum is within PSS-MAE 108 and 130. In the former (®gs. the exoccipitals (®g. 40), the exception being 23, 25), the articulated cervical vertebrae the small contributions from the supraoccip- conceal the foramen magnum and occipital ital dorsally and the basioccipital ventrally. condyles, and in the latter (®g. 40), the only As seen in PSS-MAE 130, the occipital con- substantial damage is that the bulk of the nu- dyles enclose roughly the ventral one-third chal crest and most of the bone on the right of the foramen magnum. The area of the con- mastoid exposure have been lost. dyle visible on the occiput is oval and Distinct sutures delimit the elements of the obliquely oriented, from posteroventromedial occiput in PSS-MAE 108 and 130 (®g. 40): to anterodorsolateral. Lateral to the condyle the paired mastoid portions of the petrosal is the dorsal condylar fossa, within which on laterally, the paired exoccipitals ventrome- the left side there is a minute foramen; the dially, and the supraoccipital dorsomedially. fossa on the right side has no such opening. The mastoid is distinguished from the exoc- Similar foramina in the dog transmit the con- cipital and supraoccipital by a roughly ver- dyloid vein, a tributary of the sigmoid sinus tical suture. Ventrally, this suture lies be- (Evans, 1993). tween the tympanic process of the petrosal The remaining major element on the oc- and the paracondylar process of the exoccip- ciput is the mastoid exposure of the petrosal ital (sensu Evans, 1993). From there, it runs bone (®g. 40). The ventral edge of this is dorsally between the prominence on the mas- formed by the paroccipital process laterally toid formed by the posterior semicircular ca- and extending medially from that the caudal nal and the occipital condyle. About one- tympanic process. Also visible on the occiput third of the way up the occiput, the suture ventrolateral to the paroccipital process is the runs somewhat medially to its intersection tip of the posttympanic process of the squa- with the suture between the exoccipital and mosal. The mastoid is not ¯at, but is gently supraoccipital. Dorsal to that, the mastoid su- curved, re¯ecting the contour of the enclosed ture runs vertically and then slightly laterally para¯occulus of the cerebellum. Additional- 2004 WIBLE ET AL.: ZALAMBDALESTES 85

Fig. 40. Stereophotograph of the skull of Zalambdalestes lechei PSS-MAE 130 in posterior view, with accompanying line drawing. Gray pattern represents matrix. Abbreviations: ctpp, caudal tympanic process of petrosal; eo, exoccipital; fm, foramen magnum; lmf, lower mastoid foramen; lscp, lateral semicircular canal prominence; oc, occipital condyle; pe, petrosal; pgp, postglenoid process; ppr, paroccipital process; pscp, posterior semicircular canal prominence; ptf, posttemporal foramen; so, supraoccipital; umf, upper mastoid foramen. ly, the mastoid is oriented obliquely with re- Bone loss on the right side of PSS-MAE 130 gard to the rest of the occiput and thus is also has exposed two apertures on the ventrome- partially visible in direct lateral view. Two dial and ventrolateral aspects of the mastoid, prominences over semicircular canals are respectively. The former aperture contains found on the mastoid. Lateral to the suture the unnamed common channel that bifurcates with the exoccipital and supraoccipital is the into the posterior and lateral semicircular ca- vertical prominence of the posterior semicir- nals, whereas the latter contains the lateral cular canal, which spans nearly the entire semicircular canal. height of the mastoid. Closer to the ventral Kielan-Jaworowska (1984a) reported two margin of the mastoid is the horizontal prom- foramina, one dorsolateral and the other ven- inence of the lateral semicircular canal, tromedial, in the upper part of the left mas- which spans nearly the entire breadth of the toid of ZPAL MgM-I/16. She designated mastoid. These two prominences intersect at these the upper and lower mastoid foramina. the ventromedial margin of the mastoid. Both foramina are preserved on the right side 86 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 of PSS-MAE 108, lying in the same place aperture, the posterior opening of the post- ®gured by Kielan-Jaworowska (1984a: pl. temporal canal, transmits the arteria diploeÈ- 16, ®g. 1b). Only the upper of the two mas- tica magna and accompanying vein (Wible, toid foramina appears to be preserved on the 1987; Rougier et al., 1992). In placentals, right side of PSS-MAE 130, but there is a this artery connects with the stapedial system crack through the area where the lower fo- endocranially via the ramus superior. ramen is to be expected (®g. 40). However, ENDOCRANIAL CAST: Pending our descrip- they differ from those in ZPAL MgM-I/16 in tion and analysis of high-resolution CT that the upper one is medial to the lower. As scans, the MAE sample of Zalambdalestes pointed out by Kielan-Jaworowska (1984a), provides little new information on the inter- the mastoid foramen is related to the sigmoid nal structure of the endocranium. Kielan-Ja- sinus; in the dog, it transmits a communica- worowska (1984b, 1986) has already pub- tion between the sigmoid sinus and the oc- lished on well-preserved endocasts of Za- cipital emissary vein (Evans, 1993). In extant lambdalestes, as well as Barunlestes, Asio- therians, there is usually only one mastoid ryctes, and Kennalestes, which represent the foramen per side, but Boyd (1930) reported oldest known eutherian endocasts. They have multiple mastoid foramina on one or both been described by Kielan-Jaworowska as lis- sides in 10.3% of a sample of 1500 human sencephalic, with very large olfactory bulbs, skulls. What is unusual about the mastoid fo- widely separated cerebral hemispheres in ramina in ZPAL MgM-I/16 and PSS-MAE their posterior regions, a large dorsal mid- 108 and 130 is their position entirely within brain exposure, and a comparatively short the petrosal, at a considerable distance from and wide cerebellum with well-developed the exoccipital suture (®g. 40). The typical cerebellar hemispheres. This brain condition position for the mastoid foramen is at the su- was designated by Kielan-Jaworowska ture of the mastoid and exoccipital (and (1986) as eumesencephalic, in contrast to the sometimes supraoccipital). Although the brain structure characteristic of multituber- mastoid foramen is situated entirely within culates and Triconodontidae. She (1984b) the petrosal in some forms (e.g., Lemur, Sa- concluded that Mongolian Cretaceous euthe- ban, 1963), it still approximates the exoccip- rians were probably more macrosmatic than ital suture. The position of the mastoid fo- most Tertiary and extant mammals, and she ramina reported for ZPAL MgM-I/16 and for claimed this indicated a preference for noc- PSS-MAE 108 and 130 is reminiscent of that turnal behavior in which olfaction and hear- reported for the asioryctithere Kennalestes, ing were important senses. She tentatively but not Asioryctes, by Kielan-Jaworowska estimated encephalization quotients 0.36 for (1981). Kennalestes gobiensis, 0.56 for Asioryctes In addition to the mastoid foramen, we nemegtensis, and 0.70 for Zalambdalestes found a posttemporal foramen on the occiput, lechei. previously unrecognized for Zalambdalestes. PSS-MAE 130 (®g. 19) preserves most of On the left side of PSS-MAE 130 is an elon- the dorsal and lateral surfaces of the endocast gate gap in the suture between the mastoid described for Zalambdalestes by Kielan-Ja- and squamosal, above the prominence for the worowska (1984b) based on ZPAL MgM-I/ lateral semicircular canal (®gs. 26, 40). That 14 and 16. Preserved in PSS-MAE 130 are this gap is not an artifact is con®rmed by the the lateral surfaces of the posterior part of presence of a notch in the same position on the olfactory bulbs, most of the dorsal and both sides of PSS-MAE 108 (®g. 23), where lateral surfaces of the cerebral hemispheres, the suprameatal bridge meets the nuchal the dorsal surface of the vermis and cerebel- crest. This notch is in the petrosal and would lar hemispheres, and the outer surface of the have been closed laterally by the squamosal right para¯occulus. The vessels preserved on to complete a foramen. The stereophotograph the endocast of PSS-MAE 130 are discussed of the occiput of ZPAL MgM-I/16 in Kielan- below in the Vascular Reconstruction. The Jaworowska (1984a: pl. 16, ®g. 1b) shows a endocranial dimensions (in mm) that we can gap in the same place on the specimen's left measure in PSS-MAE 130 are comparable to side. In extant mammals, the corresponding those reported by Kielan-Jaworowska 2004 WIBLE ET AL.: ZALAMBDALESTES 87

(1984b). The width of the olfactory bulb is medial opening, is elliptical and transmits 3.6 (3.5 in ZPAL MgM-I/14). The length and branches of the vestibulocochlear nerve into width of the cerebral hemispheres are 9.2 and the inner ear. Preservation does not allow us 12.8 (10.3 and 12.5 in ZPAL MgM-I/16), to identify whether the foramen acusticum and the width of the cerebellum is 9.8 (9.5 inferius has a cribriform surface for the trans- in ZPAL MgM-I/16). PSS-MAE 130 con- mission of the fascicles of the cochlear nerve ®rms Kielan-Jaworowska's (1984b) obser- (tractus spiralis foraminosus) as in other the- vations that the olfactory bulbs are not cov- rians (Meng and Fox, 1995a, 1995b) includ- ered posteriorly by the cerebrum and that the ing a petrosal referred to the Early Creta- cerebral hemispheres diverge strongly pos- ceous eutherian Prokennalestes (Wible et al., teriorly (®g. 19). There is a large gap be- 2001). The foramen acusticum superius, the tween the cerebrum and cerebellum covered smaller lateral opening, is subcircular and by the parietal in PSS-MAE 130, in the po- transmits the facial nerve to the middle ear sition where Kielan-Jaworowska (1984b) re- as well as another branch of the vestibulo- ported a broad midbrain exposure in ZPAL cochlear nerve to the inner ear. The lateral MgM-I/16. As noted by Kielan-Jaworowska edge of the foramen acusticum superius is (1984b), the central part of the cerebellum, formed by what appears to be a thin prefacial the vermis, is elevated somewhat compared commissure (®g. 41), but this has not yet to the neighboring cerebellar hemispheres, been fully prepared. Beginning at the anterior the surfaces of which are poorly preserved pole and running posteriorly along the me- in the ZPAL specimens. In PSS-MAE 130, dial edge less than half the length of the pars the well-preserved right cerebellar hemi- cochlearis is a vascular sulcus, which we in- sphere is smooth-walled and is not demar- terpret for the inferior petrosal sinus. We cated from the vermis by a furrow (®g. 19). think that this vessel left the skull via the The right para¯occulus is 4.2 mm high and anterior part of the jugular foramen, which is 2.6 mm wide, which is considerably larger represented by a notch at the posteromedial than that reconstructed by Kielan-Jaworows- broken edge of the par cochlearis (®g. 41). ka (1984b: ®g. 2). Kielan-Jaworowska In the dorsal edge of this notch is a small (1984b) was unsure of the size of the para- foramen, which we identify as the cochlear ¯occulus in ZPAL MgM-I/16, because it was canaliculus (aqueductus cochleae) for the formed from calcite rather than red sandstone perilymphatic duct. On the posterior surface as was the remainder of the brain. The fur- of the broken edge of the pars canalicularis row on the ventrolateral cerebrum tentatively is a smooth-walled depression that represents identi®ed as the rhinal ®ssure in ZPAL the anteriormost part of what was apparently MgM-I/16 by Kielan-Jaworowska (1984b) is a large subarcuate fossa. Housed within the not visible in PSS-MAE 130. subarcuate fossa was the para¯occulus of the PSS-MAE 129 preserves the endocranial cerebellum, which was well developed based surface of a partial right petrosal bone (®gs. on PSS-MAE 130 (®g. 19) and the endocast 21, 41). Much of the pars cochlearis is intact, of ZPAL MgM-I/16 (Kielan-Jaworowska, but only the most proximal pars canalicularis 1984b, 1986). Visible on the broken edge of is represented. The element is roughly tri- the pars canalicularis on either side of the angular, with the base being the broken edge preserved part of the subarcuate fossa are of the proximal pars canalicularis, including cross sections through endocasts of compo- the anterior edge of the subarcuate fossa, and nents of the membranous labyrinth of the in- the apex being the anterior pole of the pars ner ear. Ventromedial to the subarcuate fossa cochlearis. The most conspicuous feature, is the small circular endocast of the endolym- centrally located on the pars cochlearis, is a phatic duct, which runs within the aqueduc- large, subcircular depression housing the tus vestibuli. Dorsal to this is the much larger shallow internal acoustic meatus. Within the crus commune, which connected the anterior meatus are two distinct openings separated and posterior semicircular canals with the by a low transverse septum, which represent vestibule. Dorsolateral to the subarcuate fos- the foramina acusticum superius and inferius. sa is the anterior semicircular canal, and ven- The foramen acusticum inferius, the larger tral to it is the lateral semicircular canal. 88 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 41. Stereophotograph of the right petrosal of cf. Zalambdalestes sp. PSS-MAE 129 in dorsal view, with accompanying line drawing. Gray pattern represents matrix; parallel lines are damaged surfaces. Abbreviations: fai, foramen acusticum inferius; fas, foramen acusticum superius; jf, jugular foramen; pfc, prefacial commissure; sips, sulcus for inferior petrosal sinus.

Based on the endocast of ZPAL MgM-I/ basal hook region to begin its spiral course, 16, Kielan-Jaworowska (1984b: 162) report- continuing up the apex of the cochlea where ed the cochlea as ``consisting of only one the cochlear duct terminates.'' whorl'' in Zalambdalestes. However, using West's (1985) method of measuring cochlear VASCULAR RECONSTRUCTION curvature on the illustrations in Kielan-Ja- worowska (1984: ®g. 2C, pl. 31, ®g. 1b, c), The major foramina, grooves, and canals one and one-quarter turns or 450Њ appears to associated with the cranial vascular system be a better estimate for Zalambdalestes (see have already been noted in the above de- also Wible et al., 2001). West (1985: 1092) scriptions. We provide a comprehensive res- measured the number of turns in the spiral toration of the cranial vessels here to account ``starting at the in¯ection point at the round for the pathways between the major conduits window, where the cochlear duct leaves the into and out of the skull. The basis for this 2004 WIBLE ET AL.: ZALAMBDALESTES 89

Fig. 42. Reconstruction of the skull of Zalambdalestes lechei in dorsal view. Gray areas are holes. Abbreviations: ano, anterior nasal notch; as, alisphenoid; fr, frontal; ju, jugal; lac, lacrimal; mx, maxilla; na, nasal; pa, parietal; pmx, premaxilla; pop, postorbital process; sc, sagittal crest; sq, squamosal; ssf, subsquamosal foramen; tlc, translacrimal canal. restoration and the terminology employed are sue reconstruction here, we follow recent our own published and unpublished studies phylogenetic analyses (e.g., Archibald, 1996; of the cranial vessels occurring in extant Nessov et al., 1998; Rougier et al., 1998; Ji mammals (Wible, 1984, 1986, 1987, 1990; et al., 2002) that identify Zalambdalestes as Rougier et al., 1992; Wible and Hopson, an eutherian. Furthermore, our preliminary 1995; and references cited therein). Explicit hypothesis is that Zalambdalestes falls out- models for reconstructing soft tissues in fos- side of Placentalia, the crown group for the sils and for evaluating levels of con®dence living placentals (Novacek et al., 1997; No- in those inferences have been proposed by vacek, 1997; see Discussion). In light of this Bryant and Russell (1992) and Witmer hypothesis, following the terminology pro- (1995). In formulating hypotheses of soft-tis- posed by Witmer (1995), the extant phylo- 90 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 43. Reconstruction of the skull of Zalambdalestes lechei in ventral view. Gray areas are holes. Abbreviations: as, alisphenoid; bo, basioccipital; bs, basisphenoid; ecpc, ectopterygoid crest; enpc, entopterygoid crest; eo, exoccipital; gf, glenoid fossa; inf, incisive foramen; ju, jugal; mapf, major palatine foramina; mpf, minor palatine foramen; mx, maxilla; pal, palatine; pe, petrosal; pmx, premaxilla; ppt, postpalatine torus; pr, promontorium; ps?, parasphenoid; pt, pterygoid; sq, squamosal; vo, vomer. genetic bracket (minimally, the ®rst two ex- draining the dural sinuses and super®cial tant outgroups) for Zalambdalestes is placen- structures. The components of the former are tals and marsupials. Inferences that are based conservative among extant therians, but the on soft-tissue structures and osteological cor- extracranial veins vary considerably (Geld- relates occurring in both extant outgroups are eren, 1924; Wible, 1990; Wible and Hopson, considered more decisive than those occur- 1995). The major drainage of the dural sinus ring in only one. system is through the postglenoid foramen VEINS: In extant therians, the veins of the and foramen magnum in marsupials (Geld- head can be divided into the intracranial du- eren, 1924; Archer, 1976) and through these ral sinus system and the extracranial veins same apertures plus the internal jugular fo- 2004 WIBLE ET AL.: ZALAMBDALESTES 91 ramen in most placentals (Gelderen, 1924; (®g. 37D). The small jugular foramen in Za- Butler, 1967). lambdalestes transmitted the inferior petrosal The specimen of Zalambdalestes provid- sinus, based on PSS-MAE 129 (see below), ing the most information about the dural si- along with cranial nerves IX, X, and XI, nuses is the well-preserved endocast, ZPAL which did not leave much room for the sig- MgM-I/16, described by Kielan-Jaworowska moid sinus. Endocasts of the asioryctitheres (1984b). In addition to preserving the outer Kennalestes and Asioryctes have been de- contour of the brain, it shows casts for sev- scribed by Kielan-Jaworowska (1984b), but eral venous sinuses. Situated in the depres- these provide no information regarding the sion posterodorsal to the cerebral hemi- exit of the sigmoid sinus. spheres were the right and left transverse si- The endocast of PSS-MAE 130 preserves nuses. These met dorsally on the midline at the con¯uence of sinuses, the left and right the large con¯uence of sinuses. At a level transverse sinuses, and the most proximal anterodorsal to the para¯occulus of the cer- part of the left sigmoid sinus (®g. 19). In ebellum, the transverse sinus divided into addition, rostral to the con¯uence of sinuses two unequal size channels. between the cerebral hemispheres is the pos- The larger and longer distributary of the terior part of the superior sagittal sinus. This transverse sinus ran ventrally between the ce- can be traced forward only a short distance rebrum and para¯occulus. Its point of exit to where the skull roof is preserved. from the braincase cannot be traced, but was The only other component of the dural si- likely the postglenoid vein out the postglen- nus system for which there is explicit evi- oid foramen in the squamosal bone (®g. 37B, dence is the inferior petrosal sinus. This ves- D) in light of the anatomy of living therians sel occupied the groove on the endocranial (Wible, 1990). Gelderen (1924) has shown surface of the petrosal, near the basioccipital that the endocranial portion of this vein, be- suture, of PSS-MAE 129 (®g. 41) and exited tween the transverse sinus and postglenoid the braincase through the anterior part of the foramen, develops differently in marsupials jugular foramen (®g. 37D). In extant theri- on the one hand and in placentals on the oth- ans, the inferior petrosal sinus connects the er. To re¯ect this difference, he applied dif- cavernous sinus around the hypophysis (pi- ferent terms: sphenoparietal emissary vein in tuitary gland) with the internal jugular vein. marsupials and capsuloparietal emissary vein In marsupials, there is usually a canal for the in placentals. In light of the purported phy- inferior petrosal sinus between the basisphe- logenetic position of Zalambdalestes outside noid, basioccipital, and petrosal that ends at Placentalia and without developmental evi- a separate opening anterior to the jugular fo- dence for Zalambdalestes, we cannot choose ramen (Archer, 1976; Wible, 1990). In pla- which of these two patterns was present. For centals, the course of this vein is either ex- now, we employ the noncommittal term em- tracranial (i.e., ventral to the basioccipital-pe- issary vein of the postglenoid foramen for trosal suture), endocranial, or intramural (Wi- this vein in Zalambdalestes. ble, 1983). Rougier et al. (1998) coded the The smaller and shorter distributary of the course of the inferior petrosal sinus as intra- transverse sinus was the sigmoid sinus, mural for Zalambdalestes, assuming that the which ran posteriorly a short distance dorsal posterior part of the endocranial groove in to the para¯occulus. Its endocast cannot be the petrosal of PSS-MAE 129 was closed to traced to an extracranial exit. Consequently, a canal by the basioccipital. we have no direct evidence whether the sig- ARTERIES: In extant therians, three major, moid sinus left the braincase via the foramen paired arteries supply blood to the adult magnum as in marsupials or the jugular fo- head: the internal carotid and vertebral arter- ramen as in placentals. However, given the ies supply the brain, and the external carotid subequal size of the jugular foramen relative artery supplies extracranial soft tissues to the fenestra cochleae in Zalambdalestes, (Tandler, 1899, 1901). During development, as in extant marsupials (Rougier et al., 1998), an additional major paired artery, the stape- it seems likely that the principal exit was as dial artery off the internal carotid, forms in the vertebral vein out the foramen magnum all therians and sends branches that accom- 92 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 44. Reconstruction of the skull of Zalambdalestes lechei in right lateral views. Parallel lines represent cut surfaces. (A) Entire skull; (B) zygoma and rostrum removed; and (C) with major arteries (black for extracranial and gray for intracranial). Abbreviations: adm, arteria diploeÈtica magna; ap, anterior process of alisphenoid; as, alisphenoid; ea, ethmoidal artery; ecpc, ectopterygoid crest; ef, ethmoidal foramen; egp, entoglenoid process; enpc, entopterygoid crest; eo, exoccipital; fa, frontal artery; fo, foramen ovale; fr, frontal; fro, foramen rotundum; ju, jugal; ioa, infraorbital artery; iof, infraorbital foramen; la, lacrimal artery; lac, lacrimal; mapa, major palatine artery; mpa, minor palatine artery; mpf, minor palatine foramen; mx, maxilla; na, nasal; oa, ophthalmic artery; oc, occipital condyle; opf, optic foramen; otc, orbitotemporal canal; pa, parietal; pal, palatine; pe, petrosal; pop, postorbital process; pmx, premaxilla; ppr/ptp, paroccipital process/posttympanic process; pt, pterygoid; ptc, posttympanic crest; ptf, posttemporal foramen; ri, ramus inferior; rio, ramus infraorbitalis; rm, ramus mandibularis; ro, ramus orbitalis; rp, rostral process of premaxilla; rs, ramus superior; rso, ramus supraorbitalis; rt, ramus temporalis; sa, stapedial artery; smf, suprameatal foramen; so, supraoccipital; sof, superior orbital ®ssure; spa, sphenopalatine artery; spf, sphenopalatine foramen; sq, squamosal; ssf, subsquamosal foramen; tlc, translacrimal canal; V3br, branch of mandibular division of trigeminal nerve. pany the divisions of the trigeminal nerve addition, there are a few instances in extant (Tandler, 1902; Wible, 1984, 1987). How- placentals (e.g., Varecia variegata) in which ever, over the course of development in many the internal carotid artery involutes in the placentals and in all marsupials, the stapedial adult and the principal occupant of the ca- artery involutes and most or all of its end rotid groove and foramen is the internal ca- branches are annexed to the external carotid rotid nerve (Conroy and Wible, 1978). The artery (Tandler, 1899, 1901; Bugge, 1974, bones enclosing the carotid foramen also 1978, 1979; Wible, 1984, 1987). vary among extant mammals; this aperture is As discussed by Wible (1986), in extant either wholly within the basisphenoid or be- mammals, the internal carotid artery (with tween the basisphenoid and petrosal (De accompanying vein and sympathetic nerve) Beer, 1937), sometimes even in the medial follows one of three principal courses be- part of the piriform fenestra (Wible, 1986). neath the basicranium en route to its entrance In Zalambdalestes, the carotid foramen into the cranial cavity at the carotid foramen: and the groove leading to it are entirely with- (1) on the promontorium or transpromonto- in the basisphenoid (®g. 37A, B). We deem rial, (2) through the substance of the tym- it likely that the internal carotid artery, and panic wall or perbullar, or (3) medial to the not just the nerve, were present, because the tympanic wall or extrabullar. The artery's ex- former is the principal occupant of similar tracranial course may or may not be marked structures in the vast majority of taxa in the by a groove or canal on the ventral basicra- extant phylogenetic bracket (marsupials and nial surface, which complicates the recon- most placentals). Given the extreme medial struction of this vessel in extinct forms. In position of the carotid groove in Zalambda- 2004 WIBLE ET AL.: ZALAMBDALESTES 93

Fig. 44. Continued. lestes (®g. 37D), we think it most likely that Ji et al., 1999, 2002), a transpromontorial its internal carotid artery had an extrabullar groove is preserved in two proximate out- course, which among extant forms is found groups to Theria, i.e., multituberculates (Wi- in monotremes, marsupials, perissodactyls, ble and Rougier, 2000) and the prototribo- hyracoids, and some rodents and lagomorphs sphenidan Vincelestes (Rougier et al., 1992), (Wible, 1986). It has been suggested (e.g., and also in Daulestes (McKenna et al., 2000) Presley, 1979) that a medial position for the and a petrosal from the Mongolian Early artery is the primitive condition, preserved in Cretaceous referred to the basal eutherian monotremes, marsupials, and some placen- Prokennalestes (Wible et al., 1997, 2001). tals. However, in light of recent phylogenies Consequently, the extrabullar course in mar- (e.g., Rougier et al., 1996; Hu et al., 1997; supials and Zalambdalestes has most likely 94 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 been convergently acquired. In light of the penetrated an intracrural foramen in the sta- position of the carotid foramen, a medial pes. Beyond the stapes, a well-developed fo- pathway for the internal carotid is also indi- ramen and groove indicate the presence of cated in Barunlestes (®g. 4D; Kielan-Jawo- the ramus superior and ramus inferior, re- rowska and Tro®mov, 1980) and asiorycti- spectively (®g. 37D). A groove on the pro- theres (Kielan-Jaworowska, 1981; personal montorium for the stapedial artery is also obs.). A transpromontorial groove is also found, for example, in Barunlestes (Kielan- lacking from isolated petrosals referred by Jaworowska and Tro®mov, 1980), Kulbeckia Archibald et al. (2001) to the following Late (Archibald et al., 2001), Kennalestes (Kie- Cretaceous Asian taxa: Kulbeckia kulbecke, lan-Jaworowska, 1981), Ukhaatherium Eoungulatum kudukensis, Parazhelestes mi- (Rougier et al., 1998), Prokennalestes (Wible nor, and Parazhelestes robustus. With only et al., 1997, 2001), Daulestes (McKenna et isolated petrosals, it is not possible to choose al., 2000), Vincelestes (Rougier et al., 1992), whether the internal carotid was medially po- and some multituberculates (Kielan-Jawo- sitioned, as in Zalambdalestes, or on the pro- rowska et al., 1986; Wible and Rougier, montorium, with no sulcus for it, as occurs 2000). in some extant lipotyphlans (MacPhee, The ramus superior of the stapedial artery 1981). is indicated in Zalambdalestes by the later- As discussed by Wible (1987), in extant ally directed foramen between the petrosal placentals, the only structure to occupy a and squamosal (®g. 37B, D), which leads groove on the promontorium directed at the into the cranial cavity. Among extant mam- fenestra vestibuli is the stapedial artery. This mals, similarly situated foramina for the ra- branch of the internal carotid artery invari- mus superior occur in the platypus and some ably penetrates the intracrural foramen in the placentals, although in the former the fora- stapes (Novacek and Wyss, 1986b; Wible, men is between the petrosal and the lamina 1987). Grooves directed at the fenestra ves- obturans (Wible and Hopson, 1995), an in- tibuli are lacking in extant monotremes and dependent ossi®cation that fuses with the pe- marsupials, in which the stapedial artery is trosal to form the anterior lamina in the adult absent with one exception; in the platypus, (Presley, 1981; Zeller, 1989). Among extinct this vessel is present, but it runs wholly lat- taxa, the foramen for the ramus superior eral to the promontorium and fenestra vesti- (pterygoparoccipital foramen) appears to be buli (Tandler, 1899; Wible, 1987). Beyond entirely within the petrosal in multitubercu- the stapes, in its embryonic pattern in pla- lates (Kielan-Jaworowska et al., 1986; Wible centals and the platypus, the stapedial artery and Rougier, 2000), Vincelestes (Rougier et has two major branches: the ramus superior, al., 1992), and Prokennalestes (Wible et al., supplying a ramus supraorbitalis with the 2001), and between the petrosal and squa- ophthalmic nerve, and the ramus inferior, mosal in triconodontids (Rougier et al., supplying a ramus infraorbitalis and mandi- 1996), a petrosal possibly of the symmetro- bularis with the maxillary and mandibular dont Gobiodon from the Mongolian Early nerves, respectively (Tandler, 1902; Wible, Cretaceous (Wible et al., 1995), leptictids 1984, 1987; Wible and Hopson, 1995). (Rougier et al., 1998), and probably also Ba- Zalambdalestes had a well-developed sta- runlestes (see Kielan-Jaworowska and Tro- pedial artery, given the size of the groove on ®mov, 1980: ®g. 2). the promontorium directed at the fenestra Other foramina in Zalambdalestes indicate vestibuli (®g. 37B, D). In light of the extra- the presence of three sorts of branches that bullar course for the internal carotid, the sta- arose from the ramus superior within and pedial artery likely arose outside the middle then exited from the cranial cavity (®g. 44C). ear (®g. 37D), as occurs in the platypus and (1) The ramus supraorbitalis (and accompa- some rodents among extant mammals (Wi- nying vein) utilized the foramen in the back ble, 1984, 1987), and then penetrated the of the orbit identi®ed by Kielan-Jaworowska (membranous?) tympanic wall. Within the (1984b: pl. 30, ®g. 1a) on a stereophotograph middle ear, the stapedial artery ran in its of ZPAL MgM-I/16. She labeled this aper- groove to the fenestra vestibuli and likely ture as the sinus canal foramen, which is 2004 WIBLE ET AL.: ZALAMBDALESTES 95 equivalent to the term we employ, the ante- (MacPhee and Cartmill, 1986). (3) The ar- rior opening of the orbitotemporal canal. We teria diploeÈtica magna utilized the posttem- have also found the orbitotemporal canal, poral foramen on the occiput (®g. 40). Sim- presumably between the alisphenoid and pa- ilar foramina are widely distributed among rietal, on the right side of PSS-MAE 130 (®g. extant mammals (and their extinct relatives) 29). Posterior to and continuous with this, the and transmit the arteria diploeÈtica magna and exposed brain endocast has a longitudinal accompanying vein (Hyrtl, 1853, 1854; sulcus that indicates the position of the or- Tandler, 1899, 1901; Wible, 1987; Rougier et bitotemporal vessels. Within the orbit, the ra- al., 1992, 1996). This artery either serves as mus supraorbitalis likely sent arteries with an anastomosis between the occipital artery the end branches of the ophthalmic nerve, and ramus superior (e.g., Tachyglossus, Da- that is, a lacrimal artery, an ethmoidal artery sypus, Tandler, 1901; Bugge, 1979) or as a in the ethmoidal foramen, and a frontal artery branch of the ramus superior to the epaxial perhaps passing through the canal in the lac- muscles of the occiput (e.g., Petrogale,Wi- rimal onto the face. Among extant mammals, ble, 1987). the anterior opening of the orbitotemporal The ramus inferior of the stapedial artery canal transmits the ramus supraorbitalis (and is indicated in Zalambdalestes by the well- accompanying vein) in the echidna (Tandler, developed groove on the tegmen tympani ex- 1901; Rougier et al., 1992) and various pla- tending forward from the foramen for the ra- centals (Wible, 1984, 1987), and among ex- mus superior (®g. 37B, D). Among extant tinct taxa is found, for example, in most mul- mammals, a similar groove transmits the ra- tituberculates (Kielan-Jaworowska et al., mus inferior in the platypus, where it lies on 1986; Wible and Rougier, 2000), Vincelestes the contribution from the lamina obturans to (Rougier et al., 1992), asioryctitheres (Kie- the lateral trough (Wible and Hopson, 1995), lan-Jaworowska, 1981; Rougier et al., 1998), and in various placentals (e.g., Echinosorex, leptictids (Rougier et al., 1998), and probably Cartmill and MacPhee, 1980). Among ex- Daulestes (McKenna et al., 2000). (2) Tem- tinct mammals, a similar groove on the pe- poral rami to the temporalis muscle utilized trosal occurs in multituberculates, where it is the subsquamosal and suprameatal foramina enclosed in a canal (Wible and Rougier, on the side wall of the braincase above the 2000), triconodontids (Rougier et al., 1996), external acoustic meatus (®gs. 18, 23). Sub- the petrosal possibly of Gobiodon (Wible et squamosal foramina for temporal rami are al., 1995), and Vincelestes (Rougier et al., widely distributed among extant (and extinct) 1992). therians (Cope, 1880; Cartmill and MacPhee, As is the case with the ramus inferior in 1980; Novacek, 1986a; Wible, 1987), but su- the platypus and the vast majority of placen- prameatal foramina are more restricted (No- tals (Tandler, 1899; Wible, 1987), the bulk of vacek, 1986a). Among extant mammals, the the blood in this vessel in Zalambdalestes suprameatal foramen is known to transmit an probably continued forward to the orbit as artery and accompanying vein, but there are the ramus infraorbitalis with accompanying two different sources for the artery. In Di- veins to ramify with the end branches of the delphis, it arises from the ramus superior maxillary nerve. En route, near the foramen remnant in the cranial cavity and exits the ovale, the ramus inferior may also have sup- skull to supply the temporalis muscle (Wible, plied a ramus mandibularis with the mandib- 1987), whereas in Tarsius, the posterior au- ular nerve, as in most placentals (Tandler, ricular artery sends a meningeal branch into 1899; Wible, 1987). Among extant mam- the cranial cavity (MacPhee and Cartmill, mals, the ramus infraorbitalis (or maxillary 1986). We think it more likely that the su- artery of some authors, e.g., Evans, 1993) prameatal foramen in Zalambdalestes exhib- follows one of three sorts of pathways to the ited the opossum pattern. As in Zalambda- orbit from the ear region (Wible, 1987): (1) lestes, the suprameatal and subsquamosal fo- ventral to the skull base or extracranial, (2) ramina co-occur in Didelphis, with both dorsal to the skull base or endocranial, or (3) transmitting temporal rami (Wible, 1987); through an alisphenoid canal in the skull base the tarsier has only a suprameatal foramen or intramural. Given that an alisphenoid ca- 96 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 nal is lacking in Zalambdalestes, we are left sov et al. (1998), Rougier et al. (1998), Meng with either an extra- or endocranial course. and Wyss (2001), Archibald et al. (2001), Of these two, the latter is the more likely, and Ji et al. (2002). Unfortunately, these because the groove for the ramus inferior in studies, with the exception of Archibald et the tegmen tympani in PSS-MAE 130 dial. (2001), were speci®cally designed to test rected the ramus infraorbitalis toward the pir- the phylogenetic relationships of Late Cre- iform fenestra, which in turn opened into the taceous taxa other than Zalambdalestes: An- cranial cavity (®g. 37D). An endocranial agalidae in the case of Hu (1993), ``Zheles- course is unusual among extant forms, being tidae'' in the case of Archibald (1996) and found in dipodoid rodents (Bugge, 1971; Wi- Nessov et al. (1998), Deltatheridiidae in the ble, 1984) and some chiropterans (Kallen, case of Rougier et al. (1998), Tribospheno- 1977; Wible and Davis, 2000), but has also mys in the case of Meng and Wyss (2001), been reconstructed for Asioryctes (Kielan-Ja- and Eomaia in the case of Ji et al. (2002). worwoska, 1981), Vincelestes (Rougier et al., None of these studies, including Archibald et 1992), and multituberculates (Wible and al. (2001), includes enough taxonomic and Rougier, 2000). In the extant forms, the en- morphological breadth to evaluate the phy- docranial ramus infraorbitalis enters the orbit logenetic relationships of Zalambdalestes. with the maxillary nerve via the con¯uent Nevertheless, we use these studies as the superior orbital ®ssure and foramen rotun- starting point in our discussion, because our dum. In Zalambdalestes, it likely accompa- descriptions of the MAE specimens have af- nied the maxillary nerve through the fora- fected some of the character scoring by these men rotundum. Within the orbit (®g. 44C), authors. We amended and reran these matri- the ramus infraorbitalis likely sent an infra- ces employing the same parameters speci®ed orbital artery into the infraorbital canal, a in the original publications in order to eval- major palatine and sphenopalatine artery into uate the impact of the MAE specimens. Al- the sphenopalatine foramen, and a minor pal- though we do not agree with the choice of atine artery into the minor palatine foramen. all characters in these analyses, we did not A fourth branch that may have arisen from eliminate any from our reanalyses. A com- the ramus infraorbitalis was a ramus orbital- prehensive phylogenetic analysis designed to is. In extant monotremes and various placen- test the phylogenetic relationships of basal tals, this vessel connects the ramus infraor- therians, including Zalambdalestes, and bitalis and supraorbitalis (Tandler, 1899, crown-group Placentalia is a goal of our on- 1901; Bugge, 1974; Wible, 1984, 1987). It going research. may have arisen within the orbit, the usual HU (1993): Hu (1993) constructed a data condition, or within the cranial cavity and matrix of 28 dental characters across 17 ex- then exited via the superior orbital ®ssure as tinct Asian endemic eutherians and a hypo- in some megachiropterans (Wible, 1984). thetical outgroup to evaluate the relationships Among extant mammals, an ophthalmic of the Anagalidae. Six taxa with considerable artery derived from the cerebral circulation missing data were removed from the Hennig and accompanying the optic nerve is found 86 analysis, which produced a single tree in the echidna, marsupials, and many placen- with Pseudictops and Astigale as the succes- tals (Tandler, 1899, 1901; Bugge, 1974; Wi- sive outgroups to Anagalidae (®g. 45A). Of ble, 1984). In light of this distribution, an the 28 characters, we amend the coding of ophthalmic artery likely occupied the optic two for Zalambdalestes. foramen in Zalambdalestes (®g. 44C). (1) Incisor formulaÐI3/i3 (0) or I2±3/i3, I2/i2±3, or I2/i2 (1). Hu (1993: character 1) DISCUSSION scored Zalambdalestes as having three upper and lower incisors. Our report has shown the PREVIOUS PHYLOGENETIC ANALYSES upper incisor count to be variable, with some To date, Zalambdalestes has been included Zalambdalestes specimens (e.g., AMNH as a terminal taxon in seven recent phylo- 21708) having only two premaxillary inci- genetic analyses that have published data sors and others (e.g., PSS-MAE 130) having matrices: Hu (1993), Archibald (1996), Nes- an additional incisor in the maxilla. Conse- 2004 WIBLE ET AL.: ZALAMBDALESTES 97

Fig. 45. Relationships of Anagalidae and outgroups. A. The most parsimonious tree produced by Hennig 86 analysis of Hu's matrix of 28 dental characters (Hu, 1993: ®g. 7(I)). Anagalidae is the clade with Eosigale and Huaiyangale at the base. B. The strict consensus of two equally most parsimonious trees produced by PAUP analysis of Hu's matrix with our amendments to two character states for Zalambdalestes; the same result is achieved whether the multistate characters are treated unordered or ordered. quently, we scored Zalambdalestes as I2±3/ results were achieved whether the multistate i3. characters were ordered or not. (2) CaninesÐdouble-rooted (0), single- In conclusion, the original matrix of Hu rooted and moderate (1), or single-rooted and (1993) and our amended version offer lim- large (2). Hu (1993: character 2) scored Za- ited tests of Zalambdalestes af®nities, be- lambdalestes as having double-rooted ca- cause they sample only one other Cretaceous nines. The upper canine is double rooted, but eutherian and include only a narrow sample the lower has only one root and is reduced of dental characters. compared to the upper canine. Consequently, ARCHIBALD (1996) AND NESSOV ET AL. we scored Zalambdalestes as polymorphic: (1998): Archibald (1996) constructed a data double-rooted for the upper, and single-root- matrix of 18 characters of the upper postca- ed and moderate for the lower. nine dentition across 19 Late Cretaceous ter- Amending the scoring of Zalambdalestes minal taxa to evaluate the relationships of the for these two characters had an effect on the ``Zhelestidae'' from Uzbekistan. Nessov et number of equally most parsimonious trees al. (1998) added two more outgroups, Pur- and on the topology of the strict consensus gatorius and Tribosphenomys, to the matrix tree produced through analysis with PAUP of Archibald (1996). The results of both (Swofford, 2002). Using his matrix of 18 analyses with PAUP identi®ed ``Zhelestidae'' characters across 18 taxa, Hu (1993) recov- as a paraphyletic assemblage of basal mem- ered one most parsimonious tree with Hennig bers of the ungulate lineage, and Archibald 86 that placed Zalambdalestes and Kenna- (1996) coined the term Ungulatomorpha for lestes as the successive outgroups to the re- the clade including ``Zhelestidae'' and Un- maining endemic Asian taxa (Anagalidae, gulata (represented by Protungulatum in his Pseudictops, and Astigale) (®g. 45A). Our analysis). Of the 18 characters employed by amended matrix recovered two equally most these authors, we amend the coding of four parsimonious trees with PAUP, one of which for Zalambdalestes or Barunlestes. was identical to Hu's (1993) tree. The second (1) Stylar shelfÐwide (0) or narrow (1). tree reversed the positions of Zalambdalestes Archibald (1996: character e) and Nessov et and Kennalestes. The strict consensus of al. (1998: character 5) scored Zalambdalestes these two trees has a trichotomy with Za- as polymorphic for stylar shelf width, which lambdalestes, Kennalestes, and the remain- we think not re¯ective in light of the taxa ing endemic Asian taxa (®g. 45B). The same considered by these authors. Scored as nar- 98 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 row in their matrix was the stylar shelf on Amending the scoring of Zalambdalestes the very similar molars of Barunlestes.We and Barunlestes for these four characters had follow Clemens and Lillegraven (1986), who an effect on the number of equally most par- categorized the stylar shelf development in simonious trees and on the topology of the both taxa as ``narrowed'' (see ®gs. 9, 10D) strict consensus tree produced through anal- in comparisons with most of the outgroup ysis with PAUP (Swofford, 2002), following taxa considered by Archibald (1996) and the methods speci®ed in Archibald (1996) Nessov et al. (1998). and Nessov et al. (1998). Using their matrix (2) Ecto¯exusÐdeep (0), shallow (1), or of 18 characters across 19 taxa, Archibald none (2). Archibald (1996: character m) and (1996) and Nessov et al. (1998) recovered Nessov et al. (1998: character 13) scored Za- four equally most parsimonious trees, the lambdalestes as having a deep ecto¯exus and strict consensus of which placed Zalambda- Barunlestes as polymorphic: deep and shal- lestes and Barunlestes as sister taxa in a low. We are uncertain how to evaluate this clade with Asioryctes, in turn grouped in a character, because a particular tooth position polytomy with Batodon, Cimolestes, and was not speci®ed and the condition of the Gypsonictops (®g. 46A). The grouping of za- ecto¯exus varies from tooth to tooth (®g. 9). lambdalestids and Asioryctes was based on a Nevertheless, the condition in Zalambdales- single synapomorphy: postparaconular and tes resembles that in Barunlestes, Gypsonic- premetaconular cristae are weak or absent. tops, and Cimolestes, all of which were said Our amended matrix recovered 44 equally to be deep and shallow (0 and 1), and we most parsimonious trees, the strict consensus score Zalambdalestes accordingly. of which placed Zalambdalestes and Barun- (3) Metacone or metaconal swelling on P5 lestes as sister taxa at a polytomy with all the (or ultimate upper premolar)Ðabsent (0) or other nonungulatomorph taxa, with the ex- present (1). Archibald (1996: character i) and ception of Paranyctoides and Sailestes, Nessov et al. (1998: character 9) scored Za- which were allied with Ungulatomorpha (®g. lambdalestes as having a metaconal swelling 46B). Using the matrix of 18 characters on the last upper premolar (®gs. 9, 10A), the across 21 taxa (adding Purgatorius and Tri- condition noted by Kielan-Jaworowska bosphenomys), Nessov et al. (1998) recov- (1969a). In contrast, Barunlestes was scored ered 414 equally most parsimonious trees, as not having a metaconal swelling. This the strict consensus of which placed Zalamb- does not agree with Kielan-Jaworowska and dalestes and Barunlestes as sister taxa at a Tro®mov's (1980: 178) observation ``that an polytomy with Asioryctes, Batodon, Cimo- incipient metacone is here [in Barunlestes] lestes, Kennalestes, and a clade composed of somewhat larger and more strongly pro- all the remaining terminal taxa except the nounced'' than in Zalambdalestes. We follow basally positioned hypothetical ancestor and Kielan-Jaworowska and Tro®mov here. Otlestes that did not identify a monophyletic (4) Base of paracone and metaconeÐ Ungulatomorpha (®g. 46C). Our amended merged (0) or separate (1). Archibald (1996: matrix recovered 150 equally most parsi- character p) and Nessov et al. (1998: char- monious trees, with the strict consensus acter 16) scored the base of the paracone and grouping Zalambdalestes and Barunlestes as metacone as separate for Zalambdalestes (as sister taxa in a clade with Cimolestes, which did Rougier et al., 1998: character 30) and was the outgroup of all the remaining ter- as merged for Barunlestes. Kielan-Jawo- minal taxa except the basally positioned hy- rowska and Tro®mov (1980: 178) reported pothetical ancestor and Otlestes (®g. 46D). In the M1±3 to be heavily worn or damaged in fact, Zalambdalestes and Barunlestes were all specimens of Barunlestes, but noted these actual taxonomic equivalents (Wilkinson, teeth ``do not differ in any details from those 1995) in our analysis, with the same scoring of Zalambdalestes.'' In light of this and the for all characters. Supporting the grouping of stereophotographs of PIN 3142±701 in Kie- zalambdalestids and Cimolestes was a single lan-Jaworowska and Tro®mov (1980: pl. 2, synapomorphy: the linguo-labial width of ®g. 1b), we score the paracone and metacone M3 is markedly narrowed. as separate in Barunlestes. In conclusion, the original matrices of 2004 WIBLE ET AL.: ZALAMBDALESTES 99

Archibald (1996) and Nessov et al. (1998) as men as absent for Zalambdalestes based on well as our amended versions, reinforced the the MAE and CAE specimens and on the de- remarkable similarities in the postcanine den- scriptions in Kielan-Jaworowska and Tro®- titions of Zalambdalestes and Barunlestes, mov (1981). Rougier et al. were unaware of supporting the close phylogenetic relation- the later observation in Kielan-Jaworowska ships of these taxa. However, only a limited and Dashzeveg (1989) of what appears to be context for evaluating the broader relation- a labial mandibular foramen in PIN 3143± ships of zalambdalestids was offered in these 501. In light of that description, we score Za- analyses, because of the narrow taxonomic lambdalestes as polymorphic. and morphological scope. (3) Condyle shapeÐovoid (0) or cylindri- ROUGIER ET AL. (1998): Rougier et al. cal (1). Rougier et al. (1998: character 71) (1998) constructed a data matrix of 156 cran- coded the shape of the mandibular condyle iodental characters across 48 taxa to evaluate as cylindrical for Zalambdalestes. Additional the relationships of Deltatheridiidae from the preparation reveals that it is more ovoid in Late Cretaceous of Mongolia and Uzbeki- PSS-MAE 108 and 129. stan. The results of their analysis identi®ed (4) Lacrimal foramen numberÐdouble (0) Deltatheridiidae as basal metatherians, at a or single (1). The number of lacrimal foram- trichotomy with Holoclemensia and a clade ina was reported as unknown for Zalamb- of all other metatherians. In their description dalestes by Rougier et al. (1998: character of the ear region of Prokennalestes, Wible et 89). PSS-MAE 108 and 135 have two lacri- al. (2001) amended the scoring of ten basi- mal foramina, in addition to the translacrimal cranial character states in the Rougier et al. canal, the unusual canal that penetrates from (1998) matrix, eight of which were based on the orbital to the facial process of the lacri- the examination of the new specimens of Za- mal, which may have transmitted frontal ves- lambdalestes described here. These changes sels and nerves (®gs. 24, 44C). We think that did not alter the number and topology of the the single lacrimal foramen reported for Za- most parsimonious trees recovered by Roug- lambdalestes by Gregory and Simpson ier et al. (1998). In addition to the changes (1926a) is really the orbital aperture of this made by Wible et al. (2001), we amend 13 unusual canal. Consequently, we score Za- more characters states in Zalambdalestes. All lambdalestes as having two lacrimal foram- 21 of the changes to the scoring of Zalamb- ina. dalestes in the Rougier et al. (1998) matrix (5) Postpalatine torusÐabsent (0) or pre- are treated below; nine are resolutions of un- sent (1). Kielan-Jaworowska (1984a: 111) re- certainties and the remainder are changes in ported the postpalatine torus in Zalambda- coding. lestes to be ``very faint, developed only lat- (1) CentrocristaÐstraight (0) or V-shaped erally, while in the middle it widens anteri- (1). Rougier et al. (1998: character 31) orly and becomes con¯uent with the scored the upper molar centrocrista (the crest remaining portion of the palatine bone.'' between the paracone and metacone, i.e., Rougier et al. (1998: character 95) treated the postparacrista and premetacrista) as V- postpalatine torus as a binary character and, shaped for Zalambdalestes. In reviewing this following Kielan-Jaworowska (1984a), cod- character, we note that the centrocrista in Za- ed it as absent for Zalambdalestes. This ap- lambdalestes (®gs. 9, 10D) is not as straight pears to be the condition in AMNH 21708 as in other Cretaceous eutherians (e.g., Ken- (®g. 32) and in stereophotographs of ZPAL nalestes, Asioryctes), but it is also not as ex- MgM-I/14 and 16 (Kielan-Jaworowska, tremely V-shaped as occurs in some meta- 1969a: pl. 27, ®gs. 1a, 2). However, at least therians (e.g., Pucadelphys, Didelphis). We in AMNH 21708, the poor preservation may now think that it more correctly should be have affected this structure. In contrast, PSS- coded as straight, the condition found in oth- MAE 130 has a sizable postpalatine torus er Cretaceous eutherians. (®g. 35) that is as well developed as those in (2) Labial mandibular foramenÐpresent other taxa (e.g., leptictids) coded as strong (0) or absent (1). Rougier et al. (1998: char- by Rougier et al. (1998). In light of these acter 70) scored the labial mandibular fora- apparent differences, the most reasonable so- 100 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 46. Relationships of ``zhelestids'' and outgroups. A. The strict consensus of four equally most parsimonoius trees produced by PAUP analysis of Nessov et al.'s matrix of 18 characters of the upper postcanine dentition among Late Cretaceous taxa plus Protungulatum donnae (Nessov et al., 1998: ®g. 24B). Ungulatomorpha is the clade including the archaic ungulate P. donnae plus ``zhelestids'', with Aspanlestes aptap as the basalmost member. B. The strict consensus of 44 equally most parsimonious trees produced by PAUP analysis of the matrix employed in panel A with our amendments to three 2004 WIBLE ET AL.: ZALAMBDALESTES 101 lution is to treat this as polymorphic for Za- infraorbitalis as present for Zalambdalestes, lambdalestes. based on the small canal through the base of (6) Palatine reaches infraorbital canalÐ the left ectopterygoid crest in PSS-MAE 130 present (0) or absent (1). Rougier et al. (®g. 37B). Subsequent preparation has re- (1998: character 98) utilized as a character vealed that the canal is not present on the whether the palatine reaches the maxillary right side of the same specimen or on either foramen, the posterior opening of the infra- side of PSS-MAE 108. Additionally, it now orbital canal. They scored the condition in seems likely in light of the groove on the Zalambdalestes as unknown. It is clear on tegmen tympani directing the ramus inferior the left side of PSS-MAE 108 (®g. 24) that toward the piriform fenestra that the ramus a third element, in addition to the maxilla and infraorbitalis (the occupant of the alisphenoid lacrimal, contributes to the rim of the infra- canal in extant mammals) followed an en- orbital canal. Kielan-Jaworowska (1984a) in- docranial course to the orbit (®gs. 37D, 44C). terpreted this to be palatine based on ZPAL Consequently, we score the alisphenoid canal MgM-I/14, but we think it more likely is as absent. frontal based on PSS-MAE 108. Consequent- (10) Foramen ovale compositionÐin pe- ly, we score the palatine as not reaching the trosal (anterior lamina) (0), between petrosal infraorbital foramen. and alisphenoid (1), or in alisphenoid or be- (7) Pterygoids contact on midlineÐpre- tween alisphenoid and squamosal (2). Roug- sent (0) or absent (1). Rougier et al. (1998: ier et al. (1998: character 111) included a character 99) scored Zalambdalestes as hav- character about the composition of the fora- ing pterygoids that do not meet on the mid- men ovale in their analysis. Wible et al. line based on PSS-MAE 130. Additional (2001) have already noted that the second preparation of the nasopharyngeal trough in character state (1) was incorrectly written as this specimen has revealed an interpterygoid ``between petrosal and squamosal'' and suture (®g. 35). Consequently, we amend our amended it to the state shown above. The earlier score. foramen ovale was scored as positioned be- (8) Orbitotemporal canalÐpresent (0) or tween the petrosal and alisphenoid for Za- absent (1). The incidence of the orbitotem- lambdalestes by Rougier et al. (1998), based poral canal, which transmits the ramus su- on PSS-MAE 108, which we now know to perior to the orbit, was reported as unknown be damaged in light of PSS-MAE 130. The in Zalambdalestes by Rougier et al. (1998: latter specimen clearly shows the foramen character 103). However, Kielan-Jaworow- ovale to be between the alisphenoid and ska (1984b: pl. 30, ®g. 1a) labeled an anterior squamosal, with a small contribution from opening of the orbitotemporal canal (her si- the tegmen tympani of the petrosal (®g. nus canal foramen) on a stereophotograph of 37B). ZPAL MgM-I/16. Moreover, the canal itself (11) Glenoid fossa shapeÐconcave, open is preserved on the right side of PSS-MAE anteriorly (0) or trough-like (1). Of these two 130 (®g. 29). Consequently, we follow Wible states, the former is representative of the con- et al. (2001) in scoring the orbitotemporal dition in Zalambdalestes (®g. 37A, B). canal as present. Rougier et al. (1998: character 115) mistak- (9) Alisphenoid canalÐabsent (0) or pre- enly scored the shape of the glenoid fossa as sent (1). Rougier et al. (1998: character 107) polymorphic. scored the alisphenoid canal for the ramus (12) Glenoid process of jugalÐpresent,

← character states for Zalambdalestes and one for Barunlestes. C. The strict consensus of 414 equally most parsimonious trees produced by PAUP analysis of Nessov et al.'s matrix of Late Cretaceous taxa plus P. donnae, Purgatorius unio, and Tribosphenomys minutus (Nessov et al., 1998: ®g. 25A). D. The strict consensus of 150 equally most parsimonious trees produced by PAUP analysis of the matrix employed in panel C with our amendments to three character states for Zalambdalestes and one for Barunlestes. 102 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 with articular facet (0), present, without facet (1998: character 131) scored the paroccipital (1), or absent (2). In the reconstruction of the process as vertical for Zalambdalestes. How- skull of Zalambdalestes by Kielan-Jawo- ever, sutures preserved in PSS-MAE 130 re- rowska (1984a: ®g. 1), the jugal extends near veal that the bulk of the element in question to but does not attain the glenoid fossa and is on the squamosal bone (as the posttym- thus does not have a glenoid process (®g. panic process) and that the paroccipital pro- 4D). Kielan-Jaworowska noted that the su- cess is reduced (®g. 37A, B). Consequently, ture between the jugal and squamosal is well Wible et al. (2001) scored the paroccipital preserved on the right side of ZPAL MgM- process as indistinct for Zalambdalestes. I/16 and shown on a stereophotograph of that (16) Stapedius fossaÐtwice the size of fe- specimen (her pl. 27, ®g. 2). Although we nestra vestibuli (0) or small and shallow (1). were unable to see the suture in that ®gure, Rougier et al. (1998: character 139) scored we (Rougier et al., 1998: character 116) the condition of the stapedius fossa as un- scored Zalambdalestes according to the de- known in Zalambdalestes. Additional prep- scription by Kielan-Jaworowska, that is, the aration on PSS-MAE 130 has uncovered a glenoid process is absent. In contrast, the left stapedius fossa that is considerably larger side of PSS-MAE 130 shows that the jugal than the fenestra vestibuli (®g. 37B; see also clearly has a glenoid process reaching to the Wible et al., 2001). fossa (®g. 37A, C), but that it does not have (17) Medial process of squamosal in tym- an articular facet. In light of our uncertainty panic cavityÐabsent (0) or present (1). Mui- about the condition in ZPAL MgM-I/16, we zon (1994) has shown that borhyaenid mar- choose to score Zalambdalestes as polymor- supials have a medial process of the squa- phic for this character, either with the glenoid mosal that borders the epitympanic recess process absent or with one that does not have anterolaterally. Rougier et al. (1998: charac- a facet. ter 141) included this character in their anal- (13) Tympanic aperture of hiatus Fallo- ysis and scored the condition in Zalambda- piiÐin roof through petrosal (0), at anterior lestes as unknown. Subsequent preparation edge of petrosal (1), or absent (2). Rougier on PSS-MAE 108 and 130 reveals that the et al. (1998: character 123) reported the con- medial process of the squamosal is absent dition in Zalambdalestes as unknown. Sub- (®g. 37A, C). sequent preparation on the left ear region of (18) EctotympanicÐringlike (0), fusiform PSS-MAE 130 has revealed a hiatus Fallopii (1), or expanded (2). When the ectotympanic for the greater petrosal nerve at the anterior was ®rst discovered in PSS-MAE 108, only edge of the tegmen tympani (®g. 37B; see its medial aspect was prepared to protect this also Wible et al., 2001). fragile element. What was exposed was a (14) Complete wall separating cavum su- ringlike structure, the state scored for Za- pracochleare from cavum epiptericumÐab- lambdalestes by Rougier et al. (1998: char- sent (0) or present (1). Rougier et al. (1998: acter 142). Additional preparation has re- character 128) scored the condition of the vealed an element with a ringlike posterior wall separating the cavum supracochleare crus and an anterior crus expanded laterally (for the facial ganglion) from the cavum (®gs. 34B, 37C), and we amend our intitial epiptericum (for the trigeminal ganglion) as scoring to fusiform. unknown for Zalambdalestes. However, (19) Foramina for temporal ramiÐon pe- based on the endocranial surface of the petrosal (0), on parietal and/or squama of squa- trosal preserved in cf. Zalambdalestes sp. mosal (1), or absent (2). Rougier et al. (1998: PSS-MAE 129, it is apparent that a complete character 143) scored the absent state for Za- wall is present (®g. 41; see also Wible et al., lambdalestes, but subsquamosal foramina 2001). transmitting temporal rami have been sub- (15) Paroccipital process (sensu Wible and sequently identi®ed in the squamosal of PSS- Hopson, 1993) orientation and shapeÐver- MAE 108 (®gs. 18, 23) and AMNH 21708 tical (0), slanted, projecting anteroventrally (®gs. 17, 22; see also Wible et al., 2001). as ¯ange toward back of promontorium (1), (20) Foramen for ramus superior of sta- or indistinct or absent (2). Rougier et al. pedial arteryÐon petrosal (0), on petrosal- 2004 WIBLE ET AL.: ZALAMBDALESTES 103

Fig. 47. Relationships among selected Cretaceous and early Tertiary eutherians. A. The eutherian portion of the strict consensus of 144 equally most parsimonious trees produced by PAUP analysis of Rougier et al.'s matrix of 156 craniodental characters (Rougier et al., 1998: supplementary information; see also Wible et al., 2001). B. The eutherian portion of the strict consensus of 288 equally most parsimonious trees produced by PAUP analysis of the Rougier et al. matrix with our amendments to 21 character states for Zalambdalestes. squamosal suture (1), or absent (2). The con- dibular condyle is very high relative to the dition of the foramen for the ramus superior toothrow. Our amended analysis doubles the was reported as unknown in Zalambdalestes number of equally most parsimonious trees by Rougier et al. (1998: character 145). Sub- to 288, the strict consensus of which has a sequent preparation on the left side of PSS- single difference compared with that in MAE 130 shows that the foramen for the ra- Rougier et al. (1998) and Wible et al. (2001): mus superior lies on the suture between the the clade of Asioryctes and Kennalestes is no petrosal and squamosal (®g. 37B; see also longer supported and these taxa fall at a mul- Wible et al., 2001). tichotomy with the clade composed of Za- (21) Ascending canalÐintramural (0), in- lambdalestes and leptictids plus zhelestids tracranial (1), or absent (2). Rougier et al. (®g. 47B). (1998: character 152) scored the condition of In conclusion, this matrix, either the orig- the ascending canal, which transmits the ra- inal or amended, offers a limited test of Za- mus superior, as unknown in Zalambdalestes. lambdalestes af®nities, because it samples Given that the foramen for the ramus supe- only seven eutherian taxa and includes only rior is now known for PSS-MAE 130 (®g. limited characters to test eutherian interrela- 37B), an ascending canal must have been tionships, as evidenced by the collapse of the present as well. However, it is uncertain tenuous phyletic structure inside Eutheria re- whether the ascending canal was intramural covered in previous studies after our modi- or intracranial (see also Wible et al., 2001). ®cations of the scoring here. Amending the scoring of Zalambdalestes MENG AND WYSS (2001): Meng and Wyss for these 21 characters has an effect on the (2001) constructed a matrix of 82 osteolog- number of equally most parsimonious trees ical characters across 36 taxa in order to test and on the topology of the strict consensus the af®nities of the rodentiaform Tribosphen- tree produced through analysis with PAUP, omys from the late Paleocene of Inner Mon- following the methods speci®ed in Rougier golia, China. Their results con®rmed the bas- et al. (1998) and the amendments in Wible al position of Tribosphenomys relative to et al. (2001). In these two analyses, which crown-group Rodentia and also supported only included seven eutherian taxa altogeth- the superorder Glires (Rodentia ϩ Lagomor- er, Zalambdalestes was identi®ed as the sister pha). Of the 82 osteological characters, we taxon of leptictids in a clade with zhelestids amend the scoring of 15 here for Zalamb- in the strict consensus of 144 equally most dalestes and Barunlestes. parsimonious trees (®g. 47A). This clade, in (1) Incisor enamelÐcompletely surrounds turn, was allied with a clade composed of the tooth (0) or is restricted primarily to the Asioryctes and Kennalestes. Three synapo- labial surface (1). Meng and Wyss (2001: morphies allied Zalambdalestes and leptic- character 1) scored Zalambdalestes as having tids: stylar cusp A is very small to indistinct, enamel that completely surrounds the tooth. last lower premolar is molariform, and man- However, we score the derived state, because 104 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 the specimens that preserve this character, cf. ciduous upper incisor as small and rooted for Zalambdalestes sp. PSS-MAE 131 and 145, Zalambdalestes and Barunlestes. As stated have enamel restricted to the labial surface above, the upper incisors are not known for on the i1. McKenna (1994) reported restrict- Barunlestes, and it is uncertain whether the ed enamel for Barunlestes, but did not iden- second deciduous upper incisor is present in tify a specimen number. It is uncertain, but Zalambdalestes. the specimen in question may be a new ge- (7) Anterior surface of dI2Ðsmooth (0) or nus related to eurymylids (Fostowicz-Frelik grooved (1). Meng and Wyss (2001: char- and Kielan-Jaworowska, 2002). Consequent- acter 11) scored the anterior surface of the ly, we agree with Meng and Wyss that the second deciduous upper incisor as smooth condition in Barunlestes is unknown. for Zalambdalestes and Barunlestes, but this (2) Upper incisorsÐmore than three pairs should be ``?'' following our logic for the (0) or three or fewer pairs (1). Meng and previous character. Wyss (2001: character 4) scored Barunlestes (8) Third upper incisorÐpresent (0) or ab- as having the derived state, but we are un- sent (1). Meng and Wyss (2001: character aware of any specimen in which the incisor 15) scored the third upper incisor as present count can be observed or deduced (Kielan- in Zalambdalestes and as unknown in Ba- Jaworowska, 1975a; Kielan-Jaworowska and runlestes. Following the same rationale for Tro®mov, 1980). Therefore, we amend the the character regarding the presence/absence scoring to unknown for Barunlestes. of the ®rst upper incisor, Zalambdalestes (3) First upper incisorÐpresent (0) or ab- should be scored ``?''. sent (1). Meng and Wyss (2001: character 7) (9) Third upper incisorÐlateral to I2 (0), scored the ®rst upper incisor as present in posterior to dI2 (1), or reduced and imme- Zalambdalestes and Barunlestes. This should diately posterior to dI2 (2). Following the be scored as ``?'' for both taxa. It is uncertain logic with the previous character, this should from which position Zalambdalestes with be scored be scored ``?'' for Zalambdalestes two or three upper incisors has lost incisors and not ``1'' as was done by Meng and Wyss from the primitive eutherian condition of ®ve (2001: character 16). (Rougier et al., 1998; Ji et al., 2002) and, as (10) Upper canineÐpresent (0), reduced stated above, the upper incisor count is not (1), or absent (2). In their discussion of this known for Barunlestes. character, Meng and Wyss (2001: character (4) First upper incisorÐsmall (0) or large 17) stated that both upper and lower canines (1). For the reasons given with the previous were reduced in Barunlestes, but they scored character, this should be ``?'' for Zalambda- this taxon with ``0''. We agree with their dis- lestes and Barunlestes, and not small as cussion and amend their scoring of Barun- scored by Meng and Wyss (2001: character lestes to ``1''. 8). (11) First upper premolarÐpresent (0) or (5) Second deciduous lower incisorÐ absent (1). Meng and Wyss (2001: character small and rooted (0), evergrowing and ex- 22) scored the ®rst upper premolar as present tended beneath p3 or m1 (1), or beneath m3 for Zalambdalestes. We have shown above and beyond (2). Meng and Wyss (2001: char- that this character is polymorphic for this acter 9) scored Zalambdalestes and Barun- taxon and amend the scoring accordingly. lestes as having a small and rooted second (12) Second lower premolarÐpresent (0) deciduous lower incisor. Following the inter- or absent (1). Meng and Wyss (2001: char- pretation of Archibald and Averianov (2003), acter 23) scored the second lower premolar the second lower incisor is missing in Za- as present for Zalambdalestes. However, this lambdalestes (and by inference Barunlestes). has also been shown by us to be polymorphic It is uncertain whether there is a deciduous for this taxon, and we amend the scoring ac- tooth at this position and, therefore, this char- cordingly. acter should be scored as ``?'' for both taxa. (13) Incisive foraminaÐsmall and anteri- (6) Deciduous I2Ðsmall and rooted (0) or orly positioned (0), posteriorly positioned large and evergrowing (1). Meng and Wyss and moderately elongate (1), or posteriorly (2001: character 10) scored the second de- positioned and greatly elongate (2). Meng 2004 WIBLE ET AL.: ZALAMBDALESTES 105 and Wyss (2001: character 57) scored the in- in Meng and Wyss (2001). In the ®rst, sec- cisive foramina in Zalambdalestes and Ba- ond, and fourth analyses (all characters un- runlestes as small and positioned near the up- ordered; all characters ordered; and some bi- per incisors. The basis for their scoring is nary characters ordered as irreversible-up), unclear, given that the position of the incisive the consensus trees reported by Meng and foramina has not been previously reported Wyss (2001: ®gs. 13, 14) identi®ed the za- for these taxa (®g. 4B, D; see Gregory and lambdalestids Zalambdalestes and Barunles- Simpson, 1926a; Kielan-Jaworowska and tes as the outgroup to the clade including Tro®mov, 1980; Kielan-Jaworowska, 1984a). Leptictis, primates, elephant shrews, anagal- In light of the position and size of the inci- ids, Pseudictops, and Glires (®g. 48A). The sive foramina preserved on the right side in consensus tree of the third analysis of Meng PSS-MAE 108 (®g. 33) and on the left in and Wyss (2001: ®g. 14) shifted the position PSS-MAE 130 (®g. 7), we score these open- of Tupaia from outside the zalambdalestids ings as small and anteriorly positioned in Za- to the outgroup of the clade including pri- lambdalestes, but amend the scoring for Ba- mates, elephant shrews, anagalids, Pseudic- runlestes to ``?''. tops, and Glires (®g. 48B). The consensus (14) Postglenoid processÐpresent (0), ru- trees produced by the four analyses run with dimentary (1), or absent (2). Meng and Wyss our amended matrix collapsed the nodes (2001: character 62) scored the postglenoid around the zalambdalestids. In the ®rst three process as present in Zalambdalestes and un- analyses, the zalambdalestids were at a mul- known for Barunlestes. However, a postgle- tichotomy with Tupaia, Leptictis, and the noid process resembling that in Zalambda- clade including primates, elephant shrews, lestes is present in two specimens of Barun- anagalids, Pseudictops, and Glires (®g. 48C), lestes, ZPAL MgM-I/77 and PIN 3142±701. and in the fourth analysis, Leptictis fell with We therefore amend the scoring of Barunles- the clade including primates, elephant tes. shrews, anagalids, Pseudictops, and Glires (15) Postorbital processÐabsent (0), pre- (®g. 48D). The consensus trees of Meng and sent (1), or complete (2). Meng and Wyss Wyss's (2001) four analyses were based on (2001: character 75) scored the postorbital 44, 20, 20, and 44 equally parsimonious process as absent in both Zalambdalestes and trees, respectively, whereas ours were based Barunlestes. Our descriptions of the postor- on 132, 56, 40, and 132. In the Meng and bital process here are the ®rst for Zalamb- Wyss (2001) analyses, the monophyly of the dalestes; PSS-MAE 135 has a well-preserved zalambdalestids was supported by three syn- postorbital process (®g. 20), while the broken apomorphies: enlarged i1, signi®cant upper base of this process is identi®able on the diastema, and posterior edge of anterior zy- right side of PSS-MAE 108 (®g. 18) and on gomatic root aligning with M2 or M1. Only the left side of AMNH 21708 (®g. 17). The the latter two were so identi®ed in our re- postorbital process in PSS-MAE 135 resem- analyses. bles that scored as present by Meng and In conclusion, the matrix of Meng and Wyss in Rhombomylus (Li and Ting, 1985) Wyss (2001), either the original or with our and Anagale (McKenna, 1963). We therefore amendments, offers a limited test of zalamb- amend the scoring of Zalambdalestes to pres- dalestid af®nities, because it does not sample ent. We also amend the scoring of Barunles- additional relevant placentals and placental tes to ``?'', as the bones of the skull roof ``are stem taxa or include more relevant characters either missing or damaged in all available from the dentition, cranium, and postcra- specimens'' (Kielan-Jaworowska and Tro®- nium. However, it does serve to demonstrate mov, 1980: 170). the exclusion of Zalambdalestes and Barun- Amending the scoring of Zalambdalestes lestes from a very close position to Glires. and/or Barunlestes for these 15 characters ARCHIBALD ET AL. (2001): Archibald et al. has an effect on the number of equally most (2001) constructed a matrix of 70 osteolog- parsimonious trees and on the topology of ical characters across 25 taxa to test the af- the strict consensus trees produced through ®nities of the zalambdalestids Kulbeckia kul- the four initial analyses with PAUP speci®ed becke, Zalambdalestes lechei, and Barunles- 106 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 48. Relationships of the rodentiaform Tribosphenomys and outgroups. A. The strict consensus of 44 equally most parsimonious trees produced by PAUP analysis of the Meng and Wyss matrix of 82 characters of the dentition, cranium, and postcranium (Meng and Wyss, 2001: ®g. 13) with all characters ordered or with some binary characters ordered as irreversible-up. B. The strict consensus of 20 equally most parsimonious trees produced by PAUP analysis of the matrix employed in panel A with some multistate characters ordered (Meng and Wyss, 2001: ®g. 14). C. The strict consensus of 132 equally most parsimonious trees produced by PAUP analysis of the matrix employed in panel A with our amendments to eleven character states for Zalambdalestes and ten for Barunlestes, and all characters ordered. D. The strict consensus of 132 equally most parsimonious trees produced by PAUP (2000) analysis of the matrix employed in panel C with some binary characters as ordered irreversible-up. tes butleri to other well-described Late Cre- outgroups to Glires (®g. 49C). Of the 70 os- taceous eutherians and to two archaic teological characters, we amend the scoring members from both Ungulata and Glires. of 14 here for the zalambdalestids. Their ®rst analysis, which excluded the rep- (1) Number of upper and lower premo- resentatives from Ungulata and Glires, sup- larsÐ5/5 (0), 4±5/4±5 (1), 4/4 (2), 3±4/4 (3), ported a monophyletic Zalambdalestidae and 3/4 (4), or 2±3/1±3 (5). Zalambdalestes was a monophyletic Zhelestidae (®g. 49A). Their the only taxon scored as ``3'' by Archibald second analysis, including the members of et al. (2001: character 1), but we have shown Ungulata and Glires, identi®ed Glires (Mim- here that its premolar count is either 3/3, 4/ otona ϩ Tribosphenomys), and Barunlestes, 3, or 4/4. We rede®ne their state 3 to 4/3 and Zalambdalestes, and Kulbeckia as successive score Zalambdalestes as ``2'', ``3'', and ``5''. 2004 WIBLE ET AL.: ZALAMBDALESTES 107

Fig. 48. Continued.

(2) Relative sizes of upper incisorsÐnone imens reported by Kielan-Jaworowska are markedly larger than surrounding incisors (1969a). We do not dispute their measure- (0) or one or two are markedly larger than ments, but we obtain different results from surrounding incisors (1). Archibald et al. PSS-MAE 130, in which the measurements (2001: character 3) scored the derived state for both M1 and M2 are more than 60%. for Barunlestes. However, this should be Consequently, we score Zalambdalestes as ``?'', because the upper incisors are not pre- polymorphic for this character, ``0&1''. served in this taxon with the exception of the (4) Relative position of paraconule and root of the premaxillary tooth nearest the metaconule on M1±2Ðboth positioned in maxillary suture in ZPAL MgM-I/107 (Kie- nearly the same labiolingual plane nearer lan-Jaworowska and Tro®mov, 1980). protocone (0), paraconule positioned distinct- (3) Distance between paracone or meta- ly closer to protocone and metaconule nearer cone and protocone relative to total anterior the midpoint or even nearer metacone (1), or posterior width, respectivelyÐbetween 45 both positioned in nearly same labiolingual and 55% of crown width (0), more than 55% plane at midpoint or closer to paracone and of crown width (1), or less than 45% of metacone (2), or positioned in near midpoint crown width (2). Archibald et al. (2001: but metaconule very small or absent (3). character 19) scored Zalambdalestes as ``0'' Archibald et al. (2001: character 20) scored for this character, presumably based on spec- Zalambdalestes and Barunlestes as unknown 108 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 for the position of the upper molar conules, (8) Paraconid on penultimate lower pre- noting that all published specimens are worn, molarÐanterior basal cusp absent (0) or mi- leaving the conular positions as subject to in- nute, low anterior basal cusp (1). Archibald terpretation. We disagree with regard to Za- et al. (2001: character 40) scored the anterior lambdalestes. Crompton and Kielan-Jawo- basal cusp as present in Barunlestes, but Kie- rowska (1978: ®g. 9B) illustrated the conules lan-Jaworowska and Tro®mov (1980) specif- as in the same labiolingual plane and closer ically note that this cusp is lacking in this to the paracone and metacone (®g. 5). The form. Consequently, we amend the scoring AMNH cast (10154) of one of the least worn of Barunlestes to ``0''. upper molar series, ZPAL MgM-I/14, shows (9) Heel on ultimate lower premolarÐnot- clear evidence of the paraconule and meta- basined, trenchant with a single prominent conule on M1 in the position ®gured by cusp (0), small basin or ¯attened area, some- Crompton and Kielan-Jaworowska (1978). times occupying lingual one-half, with a sin- We follow these authors in scoring Zalamb- gle cusp (1), or well-developed, basined tal- dalestes as ``2'' for this character. onid (2). Archibald et al. (2001: character 45) (5) Each internal crista, notably the post- scored a well-developed, basined talonid on paraconular cristaÐnot distinct but forms the ultimate lower premolar in three taxa: continuous convex surface with convex or Gypsonictops, Zalambdalestes, and Barun- ¯at conular basin (0), forms distinct wall lestes. However, this is not congruent with (winglike) delineating a ¯at or convex con- the descriptions of the last two taxa in which ular basin (1), forms distinct ridge delineat- the talonid is described as ``unbasined'' (Kie- ing a distinctly concave conular basin (2), or lan-Jaworowska, 1984a). Based on casts very reduced or absent (3). As in the previ- available to us of Zalambdalestes (ZPAL ous character, Archibald et al. (2001: char- MgM-I/14) and Barunlestes (ZPAL MgM-I/ acter 21) scored Zalambdalestes and Barun- 77 and 135), we don't accept ``unbasined'' lestes as unknown for the crests associated as the appropriate descriptor and amend the with the upper molar conules. We disagree scoring to ``1''. with regard to Zalambdalestes. Crompton (10) Anteroposterior constriction or pinch- and Kielan-Jaworowska (1978: ®g. 9B) illus- ing of trigonid at midpoint of para- and pro- trated wings for both the paraconule and tocristidÐno (0) or yes (1). According to metaconule (®g. 5). We agree with these au- Archibald et al. (2001: character 49), a thors in light of the AMNH cast (10154) of unique feature of zalambdalestids among the ZPAL MgM-I/14, which in our opinion in- taxa they considered is a constriction or dicates that cristae were present with the par- pinching of the trigonid at the midpoint of aconule and metaconule on M1. However, the para- and protocristid. We agree that this because we are uncertain of the shape of the is present in Kulbeckia and Zalambdalestes, basin between the cristae, we score Zalamb- but score Barunlestes as unknown. The lower dalestes as ``1&2''. molar series of Barunlestes are too worn to (6) First lower premolarÐsmaller than or deny or con®rm the existence of this trait. subequal to second premolar (0), larger (1), (11) Labial mandibular foramenÐpresent or one or both p1 or p2 are absent. Archibald (0), variably present (1), or absent (2). Arch- et al. (2001: character 36) scored Zalamb- ibald et al. (2001: character 55) scored Za- dalestes as ``1'', which is the case when the lambdalestes as lacking the labial mandibular p2 is present. However, because the p2 is ab- foramen. However, as in our discussion sent in some specimens, Zalambdalestes above of Rougier et al. (1998), Zalambda- should be scored polymorphic ``1&2''. lestes should be scored as variably present in (7) Second lower premolar rootsÐtwo (0), light of the absence of this foramen in the one (1), or p2 absent (2). Archibald et al. MAE and CAE specimens and its reported (2001: character 38) scored Zalambdalestes presence in PIN 3143±501 (Kielan-Jawo- with two roots on the p2, which is the case rowska and Dashzeveg, 1989). when the p2 is present. However, because the (12) Stapedial ratioÐrounded, less than p2 is absent in some specimens, Zalambda- 1.8 (0) or elliptical, more than 1.8 (1). Arch- lestes should be scored polymorphic ``0&2''. ibald et al. (2001: character 62) reported on 2004 WIBLE ET AL.: ZALAMBDALESTES 109

®ve petrosals that they con®dently referred Zhelestidae was not supported; the former to Kulbeckia kulbecke with stapedial ratios was nested as stem taxa to Tribosphenomys ranging from 1.52 to 2.54, with an average and Mimotona, and the latter was inside an of 1.88. They used the average to score this ungulatomorph clade with Protungulatum taxon as having an elliptical oval window. and Oxyprimus. Analysis of the Cretaceous Given that both states were present in their taxa only with our amended matrix recovered sample, we amend their scoring to polymor- two trees, the consenus of which (®g. 49B) phic. Additionally, a stapedial ratio has not showed much more resolution than that of been reported for Barunlestes nor do pub- Archibald et al. (2001). The Zalambdalesti- lished ®gures enable one to be determined dae were united with Gypsonictops based on (see Kielan-Jaworowska and Tro®mov, two unequivocal synapomorphies (metacin- 1980). Therefore, we score this taxon as un- gulum [postprotocrista] formed of postmeta- known. The remarkable disparity in stapedial conule crista continuing on to the metastylar ratios in the sample of ®ve petrosals pur- lobe and the m2 trigonid considerably short- ported to be K. kulbecke is disconcerting. Lit- ened with the bases of the paraconid and tle is known about the variation of this fea- metaconid showing some fusion) and in turn ture in extant mammals (see Novacek and with the ungulatomorph clade. The out- Wyss, 1986b; Gaudin et al., 1996). However, groups to this resembled that recovered in such extreme variation is suggestive of either Archibald et al.'s (2001) second analysis (®g. damage to some specimens or the presence 49C). Analysis of the Cretaceous plus Tertia- of more than one taxonomic unit in the sam- ry taxa with our amended matrix recovered ple. four most parsimonious trees, the consensus (13) Lateral ¯angeÐrestricted to postero- of which (®g. 49D) differed from that of lateral corner of promontorium (0) or greatly Archibald et al. (2001) in that Zalambdales- reduced or absent (1). Archibald et al. (2001: tes and Barunlestes formed a clade supported character 68) scored Barunlestes as un- by two unequivocal synapomorphies (re- known, but enough of the petrosal is pre- duced M3/m3, and pre- and postcingula ab- served in PIN 3142±701 to report the lateral sent) and in that the relationships of Cimo- ¯ange as greatly reduced or absent. lestes and Kennalestes were unresolved. (14) ``Tympanic process'' of Kielan-Ja- In conclusion, although the matrix of worowska (1981)Ðabsent (0) or present (1). Archibald et al. (2001), either the original or Archibald et al. (2001: character 70) scored with our amendments, includes more rele- Barunlestes as unknown, but the ``tympanic vant basal eutherians than those discussed process'' is preserved on the left side of PIN previously, it still offers a very limited test 3142±701. of zalambdalestid af®nities with crown- Amending the scoring of Zalambdalestes, group Placentalia. Archibald et al. (2001) Barunlestes, and/or Kulbeckia for these 14 consider only two options, Glires and Un- characters has an effect on the topology of gulatomorpha. This is too restrictive a test, the strict consensus trees produced through which is made even more restrictive by the the two analyses with PAUP speci®ed in dearth of well-sampled basal members of Archibald et al. (2001). In their analysis of these two groups. Cretaceous taxa only, Archibald et al. (2001) JIETAL. (2002): Ji et al. (2002) construct- found 32 most parsimonious trees, of which ed a matrix of 269 craniodental and postcra- the consensus identi®ed a polytomy of all the nial characters across 42 taxa to test the af- ingroup taxa except that Zalambdalestidae ®nities of the Early Cretaceous eutherian and Zhelestidae were monophyletic (®g. Eomaia scansoria. Among the taxa included 49A). Archibald et al.'s (2001) analysis of were 13 Cretaceous eutherians, Protungula- Cretaceous taxa plus Tribosphenomys spp., tum, and the extant hedgehog Erinaceus. The Mimotona spp., Protungulatum spp., and Ox- results of their preferred analysis placed yprimus spp. resulted in two most parsimo- Eomaia at the base of Eutheria in a polytomy nious trees, of which the consensus had with Prokennalestes, Murtoilestes, and a much more resolution (®g. 49C). However, clade of the other eutherians included. Of the the monophyly of Zalambdalestidae and 269 characters, we amend only two. 110 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 49. Relationships of Zalambdalestidae and outgroups. A. The strict consensus of 32 equally most parsimonious trees produced by PAUP analysis of the Archibald et al. matrix of 70 characters from the dentition, anterior skull, mandible, and petrosal among Cretaceous taxa (Archibald et al., 2001: ®g. 3a). Zalambdalestidae (Kulbeckia, Zalambdalestes, and Barunlestes) and Zhelestidae (Paranyctoides, 2004 WIBLE ET AL.: ZALAMBDALESTES 111

(1) Coronoid (or its attachment scar)Ðpre- that occurring in the other Cretaceous euthe- sent (0) or absent (1). Kielan-Jaworowska rians, is lacking in AMNH 21708 (®g. 14) and Tro®mov (1981) speculated that the cor- and PSS-MAE 108 (based on high-resolution onoid bone was fused to the dentary in Za- CT scans). lambdalestes based on an oval swelling on (2) Labial mandibular foramen inside the the coronoid crest in PIN 3143±501. Ji et al. masseteric fossaÐabsent (0) or present (1). (2002: character 10) followed these authors Following Cifelli (1999), Ji et al. (2002: in scoring the coronoid as present in Za- character 20) scored the labial mandibular lambdalestes. Various Cretaceous eutherians foramen as absent for Montanalestes from have a raised, roughened area on the medial the Early Cretaceous of Montana. We re- side of the mandible near the juncture of the cently studied the only known specimen of ascending and horizontal rami. Included are Montanalestes (OMNH 60793) and report Prokennalestes (Kielan-Jaworowska and that a well-developed labial mandibular fo- Dashzeveg, 1989), Otlestes (Nessov et al., ramen is present. We modify the scoring of 1994, pl. 3, ®g. 1c), Asioryctes, and Kenna- Montanalestes accordingly. lestes (Kielan-Jaworowska, 1981). These ru- Altering the scoring of Zalambdalestes gosities are comparable positionally to a de- and Montanalestes for these two characters pression that more obviously served as a fac- has an effect on the number of equally most et for the coronoid bone in more basal taxa, parsimonious trees and the topology of the such as Vincelestes (Rougier, 1993), Henke- strict consensus tree using the methods spec- lotherium (Krebs, 1991), and Kuehneother- i®ed in Ji et al. (2002). These authors pre- ium (Kermack et al., 1968). Among Creta- sented two analyses, one with all multistate ceous eutherians, Montanalestes (Cifelli, characters unordered and the other with 38 1999) differs in that rather than a raised, multistate characters ordered. The former re- roughened area, it has a roughened depres- covered 50 most parsimonious trees, of sion more reminiscent of a coronoid facet. It which the consensus placed Zalambdalestes has been suggested (e.g., Kielan-Jaworow- at a polytomy with the asioryctitheres Ken- ska, 1981; Kielan-Jaworowska and Dashze- nalestes, Asioryctes, and Ukhaatherium (®g. veg, 1989) that the raised, roughened area in 50A). This clade was supported by ten un- Prokennalestes, Asioryctes, and Kennalestes equivocal synapomorphies, including two results from the fusion of the coronoid bone upper canine roots and a crista interfenes- to the mandible. We are uncertain of this in- tralis connected to the caudal tympanic pro- terpretation, but currently have no other ap- cess by a curved ridge. The asioryctithere- propriate alternative to account for this mor- Zalambdalestes clade in turn was at a poly- phology. Consequently, we do not alter Ji et tomy with Montanalestes and a clade of Late al.'s (2002) scoring of taxa other than Za- Cretaceous eutherians plus Protungulatum lambdalestes. For Zalambdalestes, we score and Erinaceus. Our amended matrix recov- the coronoid as polymorphic, because the ered 116 most parsimonious trees with the raised area described in PIN 3143±501, consensus collapsing the asioryctithere-Za- which is higher up the coronoid crest than lambdalestes clade into a polytomy with

← Gallolestes, Aspanlestes, Zhelestes, Parazhelestes, Eoungulatum, Avitotherium, and Alostera) are monophyletic. B. The strict consensus of two equally most parsimonious trees produced by PAUP analysis of the matrix employed in panel A with our amendments to eight character states for Zalambdalestes, seven for Barunlestes, and one for Kulbeckia. C. The strict consensus of two equally most parsimonious trees produced by PAUP analysis of the matrix employed in panel A with the addition of four Tertiary taxa, Mimotona, Tribosphenomys, Protungulatum, and Oxyprimus (Archibald et al., 2001: ®g. 3b). Za- lambdalestidae and Zhelestidae are paraphyletic and are allied with Glires and Ungulata, respectively. D. The strict consensus of four equally most parsimonious trees produced by PAUP analysis of the matrix employed in panel B with the addition of Mimotona, Tribosphenomys, Protungulatum, and Oxy- primus. 112 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 50. Relationships of Early Cretaceous Eomaia and outgroups. A. The strict consensus of 50 equally most parsimonious trees produced by PAUP analysis of the Ji et al. matrix of 268 dental and skeletal characters with all characters unordered (Ji et al., 2002: ®g. 6a). B. The strict consensus of 116 equally most parsimonious trees produced by PAUP analysis of the matrix employed in panel A with our amendments to one character state for Zalambdalestes and one for Montanalestes. C. The strict consensus of three most equally parsimonious trees produced by PAUP analysis of the matrix employed in panel A with some multistate characters ordered (Ji et al., 2002: supplementary information).

Montanalestes, Daulestes, Cimolestes ϩ eutherians, as well as of nonbasicranial cra- Gypsonictops, and Ungulatomorpha ϩ Eri- nial characters (which is re¯ective of what is naceus (®g. 50B). The second analysis in Ji preserved for Eomaia). et al. (2002) with some ordered characters resulted in three most parsimonious trees; the COMPARISONS consensus placed Zalambdalestes as the sister taxon of Kennalestes, with Asioryctes and In the following, the MAE specimens are Ukhaatherium as successive outgroups (®g. compared, in turn, with other Zalambdales- 50C). Three unequivocal synapomorphies tes, with Barunlestes butleri, with Kulbeckia united Zalambdalestes and Kennalestes: the kulbecke, with leptictids and insectivorans, primary cusp a and posterior cusp c on the with lagomorphs, rodents, and elephant ultimate lower premolar subequal; the para- shrews, with asioryctitheres, and with zhe- conid lingually positioned and appressed to lestids in order to address previous hypoth- the metaconid; and a nearly transverse par- eses of the lower and higher level relation- acristid. The asioryctithere-Zalambdalestes ships of Zalambdalestes. We do not intend clade was nested between Montanalestes at these comparisons to be de®nitive, but mere- the base and a clade of Murtoilestes, Proken- ly a preliminary step in assessing the phy- nalestes, and Eomaia, which in turn was the logenetic relationships of Late Cretaceous outgroup to a clade composed of the remain- Mongolian eutherians. Such a broadscale ing Late Cretaceous taxa plus Protungulatum analysis is a goal of our ongoing research, and Erinaceus. Our amended matrix recov- but is beyond the scope of the current paper. ered the same three trees and consensus. WITHIN ZALAMBDALESTES: As a result of our Although the Ji et al. (2002) matrix had descriptions of the MAE specimens, nearly by far the most characters and sampled more all aspects of the cranial anatomy of Za- anatomical regions than any analysis dis- lambdalestes lechei are now known in some cussed previously, it still offers a limited test detail, and most of the gaps in the descrip- of Zalambdalestes relationships. It contains a tions by previous authors have been com- limited sampling of other extinct and extant pleted. However, our descriptions have also 2004 WIBLE ET AL.: ZALAMBDALESTES 113 highlighted differences from those by previ- MgM-I/43. The incidence of this variability ous authors. In most instances, we think that appears valid and not the result of damage. the exquisite preservation of the MAE spec- (3) Angle of coronoid processÐAs re- imens has provided us with a sharper image ported by Gregory and Simpson (1926a), of the anatomy in question. Examples in- Kielan-Jaworowska and Tro®mov (1981), clude our identi®cation of the various orbi- and here, the angle of the coronoid process totemporal foramina, the incisive foramen, to the alveolar margin varies from 45Њ to 60Њ the postorbital process, and the posttemporal (cf. ®gs. 4B, 13, 15). Ontogenetic differences canal. Yet, we cannot rule out the possibility may account for some of this variation, as that the currently available sample of Z. lech- suggested by Kielan-Jaworowska and Tro®- ei presents individual variability, as for ex- mov (1981), with the coronoid at a lower an- ample in the degree of development of the gle in juveniles than adults. facial process of the premaxilla, the postpal- (4) In¯ection of mandibular angleÐBased atine torus, the midline crest in the nasopha- on the nearly complete angular process in ryngeal trough, the glenoid process of the ju- PIN 3143±501, Kielan-Jaworowska and Tro- gal, and the fossa for the rectus capitis mus- ®mov (1981) described this process as me- cle discussed above, or that more than one dially in¯ected for Zalambdalestes. The ste- taxon exists. The major discrepancies be- reophotographs of this specimen in occlusal tween our and previous descriptions (e.g., view (Kielan-Jaworowska and Tro®mov, Gregory and Simpson, 1926a; Kielan-Jawo- 1981: pl. 1, ®g. 1b) appear to show a slight rowska, 1969a, 1984a) are summarized be- medial deviation to the angle, but nothing low, with the caveat that we have not fully near the extent of the medial in¯ection that studied the ZPAL and PIN collections. Al- occurs in most metatherians (SaÂnchez-Villa- though we had the opportunity to peruse both gra and Smith, 1997; SaÂnchez-Villagra and collections, this unfortunately occurred at a Wible, 2002). In contrast, the complete angles in PSS-MAE 108 are not medially in- preliminary stage in the preparation of the ¯ected, but posteriorly directed (®g. 33; MAE specimens. Rougier et al., 1998: character 73). We are (1) Number of upper incisorsÐThe most unsure whether a difference in the angle ex- recent pronouncements on the dental formula ists between the PIN, MAE, and AMNH of Zalambdalestes (e.g., Kielan-Jaworowska, specimens, but we are certain that the angle 1984a; Thenius, 1989) designate three upper in Zalambdalestes is not medially in¯ected. incisors (®g. 4D), even though evidence for (5) Labial mandibular foramenÐKielan- only two exists in the CAE and ZPAL sam- Jaworowska and Dashzeveg (1989) reported ple. PSS-MAE 108, 130, and 131 show with- the presence of a labial mandibular foramen out doubt the presence of only two incisors in PIN 3143±501, and the stereophotographs within the premaxilla (®gs. 7, 23). However, in Kielan-Jaworowska and Tro®mov (1981: a discrepancy regarding a maxillary incisor pl. 2, ®g. 2a) appear to show such an opening exists: it is present in PSS-MAE 130, the behind the coronoid crest within the masse- right side of PSS-MAE 108, and perhaps teric fossa, which is damaged in this speci- AMNH 21709, and absent in AMNH 21708 men. In contrast, the MAE and AMNH spec- and perhaps ZPAL MgM-I/13. In light of the imens show no sign of this aperture (®gs. 13, unexpected nature of this tooth, the ZPAL 23, 31). sample should be reexamined. (6) Coronoid bone remnantÐKielan-Ja- (2) Number of premolarsÐThe current worowska and Tro®mov (1981) described an sample of Zalambdalestes exhibits a discrep- oval rugosity on the lower part of the as- ancy in the number of upper and lower pre- cending ramus of the mandible in PIN 3143± molars, although most specimens have four 501 and suggested that it might be a remnant in both jaws. As stated above, P1 is lacking of the coronoid bone, fused to the mandible. in PSS-MAE 130 (®g. 9) and AMNH 21704, No swelling occurs in AMNH 21708 (®g. 21708, and 21709, whereas p2 is lacking in 14) and PSS-MAE 108 (based on CT scans). PSS-MAE 129 (®g. 31), AMNH 21704 and (7) Development of facial process of pre- 21708 (®g. 12), and the right side of ZPAL maxillaÐThe CAE and MAE sample of Za- 114 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 lambdalestes exhibits two extremes in the AMNH 21708 exhibits a slight posterior in- development of the facial process of the pre- clination (®g. 22). maxilla. Its farthest extent is dorsal to the WITH BARUNLESTES BUTLERI: Comparisons posterior canine root in AMNH 21708 (®g. between Zalambdalestes and the slightly 22) and PSS-MAE 129 (®g. 31) or anterior younger Barunlestes have already been re- to the canine in PSS-MAE 108 (®gs. 23, 25) ported by Kielan-Jaworowska (1975a, and 130 (®g. 26). Based on the ZPAL sam- 1984a) and Kielan-Jaworowska and Tro®- ple, Kielan-Jaworowska (1984a) reported it mov (1980). The MAE specimens of Za- dorsal to the canine (®g. 4B). lambdalestes allow us to expand upon the (8) Position of major palatine foramenÐ observations of these authors, but we caution Based on ZPAL MgM-I/14 and 16, Kielan- that we have not yet had the opportunity to Jaworowska (1984a) reported the major study in detail the ZPAL and PIN specimens (greater) palatine foramen to be opposite the of Barunlestes in light of the MAE collec- protocone of P3 (®g. 4D). In contrast, the tion. major palatine foramen in PSS-MAE 130 is As a starting point for our comparisons, slightly more posterior, opposite the posterior we repeat here the cranial features in the re- part of the P3, and, rather than a single ap- vised diagnosis in Kielan-Jaworowska erture, it has two unequal openings (®g. 35). (1984a: 108) for Zalambdalestidae, which in- In AMNH 21708, the major palatine foramen cluded only Zalambdalestes and Barunlestes: is even more posterior, opposite the proto- ``Skull constricted in front of P1, with very cone of P4 (®gs. 4C, 32). long, narrow snout. Brain case more in¯ated (9) Development of postpalatine torusÐ than in other contemporaneous proteutheri- As mentioned above, Kielan-Jaworowska ans, zygomata slender, strongly expanded lat- (1984a) reported the postpalatine torus to be erally, post-orbital constriction present, oc- very faint based in ZPAL MgM-I/14 and 16, cipital plate inclined forwards from the condyles. Sagittal and nuchal crests present. Pal- the condition also occurring in AMNH ate without fenestrae, posterior [minor] 21708 (®g. 32). In contrast, PSS-MAE 130 palatine foramina very large, oval. Maxilla has a substantial postpalatine torus (®g. 35). extending backwards along the choanae, the (10) Components of minor palatine fora- presphenoid [?parasphenoid] with a promi- menÐIn her reconstruction of the skull of nent median process, foramen rotundum, Zalambdalestes lechei, Kielan-Jaworowska very large pterygoid [ectopterygoid] process (1984a: ®g. 2) placed the minor palatine of basisphenoid [alisphenoid], ®ssura for (posterior palatine) foramen within the suture chorda tympani, postglenoid process extend- between the maxilla laterally and palatine ing only opposite the medial part of the glen- medially and stated (ibid.: 111) that ``the oid fossa, foramen arteriae stapediae [piri- maxilla has a backward extension along the form fenestra], sulcus arteriae stapediae, no side of the palatine'' forming the walls of the sulcus arteriae promontorii.'' Of these fea- nasopharyngeal duct (®g. 4D). In contrast, tures, three are no longer applicable to Za- the left side of PSS-MAE 130 clearly shows lambdalestidae: occipital plate inclined for- that the pterygoid forms the posterolateral wards, maxilla extending backward along the border of the minor palatine foramen and choanae, and the ®ssura for the chorda tym- along with the palatine contributes to the pani. The occiput in Zalambdalestes (®g. 4B) walls of the nasopharyngeal duct (®g. 35). and Barunlestes (®g. 48B) is reported (Kie- (11) Inclination of occiputÐKielan-Jawo- lan-Jaworowska and Tro®mov, 1980; Kielan- rowska (1984a: 111) reported for Zalamb- Jaworowska, 1984a) to be inclined forwards dalestes that ``the occipital plate is inclined (about 85Њ to the plane of the teeth in the forwards from the condyles as in Kennales- latter), but as discussed above it is essentially tes and Asioryctes.'' Unfortunately, she does vertical in PSS-MAE 108 and 130 and is in- not provide any ®gures of specimens that il- clined slightly backwards in AMNH 21708. lustrate this forward inclination. In contrast, In Barunlestes and Zalambdalestes, Kielan- PSS-MAE 108 and 130 have a roughly ver- Jaworowska and Tro®mov (1980) and Kie- tical occipital plate (®gs. 23, 25, 26, 29), and lan-Jaworowska (1984a) identi®ed a narrow 2004 WIBLE ET AL.: ZALAMBDALESTES 115 process of the maxilla ventrolateral to the which is in contrast to the anterior position choanae, posterior to the minor palatine fo- we found in Zalambdalestes (®g. 37B). How- ramen (®g. 4D), but as discussed above in ever, we found the foramen anterior to the PSS-MAE 130, the corresponding area is postglenoid process in two specimens of Ba- clearly formed by the pterygoid bone. In Ba- runlestes, ZPAL MgM-I/77 and PIN 3142± runlestes, Kielan-Jaworowska and Tro®mov 701. Moreover, the former specimen has both (1980) interpreted a deep groove on the ali- suprameatal and subsquamosal foramina, sphenoid (their basisphenoid) between the previously not recognized for Barunlestes.In ectopterygoid crest and entoglenoid process light of these similarities along with the strik- as for the chorda tympani nerve, a branch of ing dental resemblances (see, for example, the facial nerve. In Zalambdalestes, this in- the data matrix in Archibald, 1996: table 1), terval includes the foramen ovale, and in there is little doubt that Zalambdalestes and PSS-MAE 130, the specimen best preserving Barunlestes are more closely related to each this region, a deep groove on the alisphenoid other than to any other known taxon. is lacking. There is a deep groove on the teg- We also note the following differences be- men tympani, but its major occupant was the tween Zalambdalestes and Barunlestes, again ramus inferior of the stapedial artery (®g. with observations on the latter based on Kie- 37A, B, D). lan-Jaworowska and Tro®mov (1980). An To the above features, we note the follow- accessory (lesser) palatine foramen in the ing additional similarities between Zalamb- maxillo-palatine suture opposite P4 occurs in dalestes and Barunlestes, with observations Barunlestes but is lacking in PSS-MAE 130 on the latter taken from the descriptions and/ (®g. 35). The minor (posterior) palatine fo- or illustrations in Kielan-Jaworowska and ramen is between the palatine, maxilla, and Tro®mov (1980): deep groove connecting pterygoid in PSS-MAE 130 (®g. 32), but it sphenopalatine and maxillary foramina; is within the maxilla or between the maxilla well-developed entopterygoid crest; squa- and palatine in Barunlestes (see Kielan-Ja- mosal contributing to foramen ovale; round- worowska and Tro®mov, 1980: ®g. 2). Two ed, midline ridge on basisphenoid; narrow lacrimal foramina occur in PSS-MAE 108 basisphenoid process within piriform fenes- (®g. 24) and 135, but only one is reported in tra; course for internal carotid artery medial Barunlestes. A postorbital process is present to promontorium; short sulcus for stapedial in PSS-MAE 108 and 135 (®g. 20) but is artery by fenestra vestibuli; promontorium lacking (damaged?) in Barunlestes (®g. with ¯at anteromedial ¯ange; foramen for ra- 51B). The orbital process of the palatine con- mus superior between petrosal and squamo- tacts the lacrimal in Barunlestes, but not in sal; tegmen tympani narrow; crista interfe- Zalambdalestes. The carotid foramina are nestralis contacting tympanic process; tym- within the basisphenoid in PSS-MAE 108 panic process on petrosal-exoccipital suture; (®g. 33) and 130 (®g. 37B, C), but they are glenoid fossa on braincase; entoglenoid pro- between the basisphenoid and petrosal in Ba- cess continuous with postglenoid process; runlestes (®g. 4D). On the occiput, the oc- well-developed trough for external acoustic cipital condyles extend about halfway up the meatus; posttympanic crest present; cerebral sides of the foramen magnum in Barunlestes, hemispheres that strongly diverge posterior- but only about one-third in PSS-MAE 130 ly; and, based on Fostowicz-Frelik and Kie- (®g. 40). In the lower jaw, Barunlestes has lan-Jaworowska (2002), root for i1 open and only one mental foramen, below the posterior extending at least below the anterior part of root of p3 (®g. 51B), whereas Zalambdales- the m1. Based on our preliminary observa- tes has two, below the anterior root of p1 and tions of Barunlestes, we add the following the middle of p3 (®g. 51A), according to similarities to this list: position of the post- Kielan-Jaworowska and Tro®mov (1981). glenoid foramen and presence of suprameatal Dental differences noted by Kielan-Jawo- and subsquamosal foramina. Kielan-Jawo- rowska (1975a) and Kielan-Jaworowska and rowska and Tro®mov (1980) tentatively rec- Tro®mov (1980) include the number of roots ognized the postglenoid foramen as posterior on the upper canine (two in Zalambdalestes to the postglenoid process in Barunlestes, versus one in Barunlestes) and the anterior 116 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 51. Reconstructions of the skulls of Asian Late Cretaceous eutherians in right lateral views to the same scale: (A) Zalambdalestes lechei, based on our report; (B) Barunlestes butleri, redrawn from Kielan-Jaworowska (1975a: ®g. 2B); (C) Kulbeckia kulbecke, redrawn from Archibald and Averianov (2003: ®g. 7C); (D) Asioryctes nemegetensis, redrawn from Kielan-Jaworowska (1975a: ®g. 1B); (E) Kennalestes gobiensis, redrawn from Kielan-Jaworowska (1975a: ®g. 1A); and (F) Daulestes nessovi, redrawn from McKenna et al. (2000: ®g. 7). basal cusps on P2 and p3 (present in Za- cian of Uzbekistan have been supplemented lambdalestes versus absent in Barunlestes). by two recent reviews that include descrip- WITH KULBECKIA KULBECKE: Nessov's tions of new material (Archibald et al., 2001; (1993) original descriptions of Kulbeckia Archibald and Averianov, 2003). In addition kulbecke from the late Turonian and Conia- to the dentition, this taxon is now known 2004 WIBLE ET AL.: ZALAMBDALESTES 117

Fig. 51. Continued.

from an anterior skull fragment that preserves most of the left snout to the midorbit (®gs. 51C, 52), as well as ®ve isolated petrosals. Based on this new material, in particular, Archibald et al. (2001) and Archibald and Averianov (2003) have assigned Kulbeckia to Zalambdalestidae, with which we concur. The phylogenetic analysis of Cretaceous eutherians published in Archibald et al. (2001) identi®ed Kulbeckia as the sister taxon of Za- lambdalestes plus Barunlestes; it was in the analysis that also included four Tertiary taxa in which zalambdalestids were paraphyletic (®g. 49C). Archibald and Averianov (2003) offer the following summary similarities between Kulbeckia, Zalambdalestes, and Ba- runlestes: ``a narrow, somewhat elongated snout, procumbent, enlarged, and open-rooted medial lower incisor with enamel restricted to the more ventrolabial surface [and a root extending at least below p2], and anteroposteriorly compressed and centrally pinched molar trigonids.'' The last is the an- Fig. 52. The palate of Kulbeckia kulbecke, re- teroposterior constriction or pinching of the drawn from Archibald and Averianov (2003, ®g. trigonid at the midpoint of the para- and pro- 7E). Dental formula preserved is I3, C, P4, M3. tocristid on m1±3 of Archibald et al. (2001). 118 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Other similarities taken from Archibald et al. that zalambdalestids were stem ``zalambda- (2001) include the bases of paracone and donts''. After studying the better preserved metacone separate, a crista interfenestralis dentition of AMNH 21709 (Simpson, connected to the caudal tympanic process of 1928a), Simpson (1928b) revisited the wider the petrosal by a curved ridge, a ``tympanic relationships of zalambdalestids and altered process'' of Kielan-Jaworowska (1981) pres- his earlier conclusion. He disassociated Za- ent (the lateral half of which is on the petro- lambdalestes from ``zalambdadonts'' and al- sal), and the absence of a transpromontorial lied them with leptictids, noting the remark- sulcus. According to Archibald and Averi- able similarity in molar structure. Close re- anov (2003), Kulbeckia resembles Zalamb- lationships between zalambdalestids and ear- dalestes in having a translacrimal canal (ally Tertiary leptictids have been supported though it is placed more ventrally in Kul- subsequently by McDowell (1958), Van Val- beckia), a lacrimal tubercle, a weak postor- en (1967), Kielan-Jaworowska (1969a), and bital process on the frontal, the infraorbital Clemens (1973). More recent comparisons foramen at the level of the penultimate pre- have uncovered few derived resemblances in molar, the second upper incisor more later- the dentition or skull of zalambdalestids and ally compressed than the ®rst, a probable leptictids (Novacek, 1986a; Clemens and Lil- two-rooted upper canine, and the mental fo- legraven, 1986). ramina below p1 and p3 (®g. 51A, C). The Among the few cranial resemblances of condition of the ®rst three features is un- zalambdalestids and leptictids that are unusu- known in Barunlestes, whereas the last two al in their incidence among eutherians are a differ in that taxon (see above). Finally, Kul- large, common recess for the foramina trans- beckia resembles some specimens of Za- mitting the major palatine and caudal nasal lambdalestes in having a small third upper nerves and vessels (known in Zalambdales- incisor within the maxilla. tes) and a suprameatal foramen (known in According to Archibald and Averianov Zalambdalestes and Barunlestes) (®g. 53). (2003), Kulbeckia differs from Zalambdales- According to Novacek (1986a), the spheno- tes and Barunlestes in the ``probable reten- palatine recess also occurs in lipotyphlans, tion of four lower incisors, bifurcated or two- carnivorans, and aardvarks, and the supra- rooted lower canine, relatively smaller or ab- meatal foramen is also in didelphids as well sent diastemata between anterior teeth, more as some xenarthans and euprimates. The lingually placed cristid obliqua, less reduced spenopalatine recess also occurs in asioryc- M3 and m3'', lack of a metaconal swelling titheres (Kielan-Jaworowska, 1981), and the on P4, lingually placed conules on M1 and suprameatal foramen may be primitive, be- M2 (with distinct, low internal cristae), upper cause it is also present in basal metatherians molar protocones usually with small vertical (Rougier et al., 1998) and in asioryctitheres crenulation or small cuspule on the antero- (see below). Other cranial similarities (®g. and posterolingual margins of well-devel- 53) include a long anterior process of the ali- oped cingula, and trigonids not as anteropos- sphenoid that contacts the palatine (known in teriorly shortened. Additionally, Kulbeckia Zalambdalestes), well-develped ecto- and en- differs from Zalambdalestes in having what topterygoid crests (known in Zalambdalestes appears to be a foramen for the frontal di- and Barunlestes), and a small palatine con- ploic vein (Thewissen, 1989) in the frontal tribution to the orbital wall (known in Za- bone ventral to the postorbital process, ver- lambdalestes and Barunlestes). A long ante- tically implanted upper incisors, I1 and I2 rior process of the alisphenoid in contact subequal, I2 in the premaxillary-maxillary with the palatine also occurs in some extant suture (®g. 51A, C), and a lower stapedial placentals (®g. 54; Muller, 1934; McDowell, ratio, 1.52±2.54 with an average of 1.88 for 1958) and marsupials (Wible, 2003), but it is Kulbeckia (but see comments above) versus lacking in Vincelestes (Rougier, 1993; Hop- 2.3 for Zalambdalestes. son and Rougier, 1993), the basal metathe- WITH LEPTICTIDS AND INSECTIVORANS:As rian Pucadelphys (Marshall and Muizon, noted earlier, Gregory and Simpson (1926a) 1995), asioryctitheres (Kielan-Jaworowska, speculated based largely on dental evidence 1981), Daulestes (McKenna et al., 2000), 2004 WIBLE ET AL.: ZALAMBDALESTES 119

Fig. 53. The skull and lower jaw of the leptictid Leptictis dakotensis in right lateral view, redrawn from Novacek (1986a: ®gs. 1, 10). Parallel lines indicate the cut surfaces of the zygoma. Abbreviations: an, (mandibular) angle; ap, anterior process of alisphenoid; as, alisphenoid; asc, alisphenoid canal; con, (mandibular) condyle; ecpc, ectopterygoid crest; en, entotympanic; enpc, entopterygoid crest; fdv, foramina for frontal diploic vein; fr, frontal; lact, lacrimal tubercle; ma, mandible; mx, maxilla; os, orbitosphenoid; pa, parietal; pal, palatine; pmx, premaxilla; smf, suprameatal foramen; sq, squamosal; ssf, subsquamosal foramen. and the Eocene palaeoryctid Eoryctes and Gingerich, 1989). Leptictids resemble (Thewissen and Gingerich, 1989). Well-de- Barunlestes, and not Zalambdalestes, in that veloped ecto- and entopterygoid crests also the palatine contacts the lacrimal (®g. 53). occur in asioryctitheres (®g. 56B; Kielan-Ja- Leptictids differ from zalambdalestids in nu- worowska, 1981) and some extant placentals merous features including the presence of a (Novacek, 1986a), but they are lacking in well-developed entotympanic bulla, absence Vincelestes (Rougier, 1993), Daulestes (Mc- of a foramen rotundum, broad dorsal contact Kenna et al., 2000), and Eoryctes (Thewissen between the maxilla and frontal, and small and Gingerich, 1989). Regarding the palatine facial exposure of the lacrimal (®g. 53). in the orbit, a small contribution also occurs Two recent phylogenetic analyses have in some extant placentals (®g. 57; Muller, linked leptictids and Zalambdalestes.In 1934; Novacek, 1980, 1985), but it is more Rougier et al.'s (1998) analysis of the rela- extensive in Vincelestes (Rougier, 1993), tionships of Deltatheridiidae, which included metatherians (Wible, 2003), asioryctitheres seven eutherian taxa altogether, Zalambda- (Kielan-Jaworowska, 1981), Daulestes (Mc- lestes was identi®ed as the sister taxon of Kenna et al., 2000), and Eoryctes (Thewissen Leptictis in a clade with ``zhelestids'' (®g. 120 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

47A). Three synapomorphies allied Zalamb- ical de®nition of the family Zalambdalestidae dalestes and Leptictis: stylar cusp A is very or genus Zalambdalestes. However, previous small to indistinct, last lower premolar is mo- usage of the root of this nomen by Gill sug- lariform, and mandibular condyle is very gests that Gregory and Simpson (1926) high relative to the toothrow (®g. 53). In [1926a] chose their generic and familial no- Archibald et al.'s (2001) analysis of Creta- mina based on the perceived shape of the an- ceous eutherians plus four Tertiary taxa as imal's cheek teeth. The type specimen of Za- well as in our amended matrix, Gypsonic- lambdalestes lechei (AMNH 21708) has tops, a Cretaceous leptictidan according to heavily worn teeth [®gs. 12, 32], showing McKenna and Bell (1997), grouped with the transversely elongate upper molars and low- ``zalambdalestids'' plus Mimotona and Tri- ers with a tall trigonid. Material recovered bosphenomys (®g. 49C, D). Supporting this since Gregory and Simpson's description were two unequivocal synapomorphies: the (e.g., Kielan-Jaworowska, 1968 [1969a]) metacingulum (postprotocrista) formed of demonstrates that in contrast to the golden the postmetaconule crista continuing on to moles, solenodons, and tenrecs to which Gill the metastylar lobe, and the m2 trigonid con- was referring, zalambdalestids possess prom- siderably shortened with the bases of the inent metacones on their upper molars, broad paraconid and metaconid showing some fu- talonids on their lowers, and a primary oc- sion. We have stated above that both the clusal relationship between protocone and Rougier et al. (1998) and Archibald et al. talonid basin (Kielan-Jaworowska, 1968 (2001) analyses were very limited tests of the [1969a]: 187).'' Asher et al.'s (2002: 15) phylogenetic relationships of Zalambdales- conclusion is that zalambdalestids are not an- tes, because of the low number of relevant atomically zalambdadont, which they recog- taxa and characters. Interestingly, in the Ji et nize ``when the primary occlusal relationship al. (2002) analysis, which might be consid- between upper and lower cheek teeth occurs ered more inclusive in that it has postcranial between the paracone and hypo¯exid, pri- as well as cranial characters, Gypsonictops mary shearing occurs between the prepara- did not fall with Zalambdalestes, but was al- crista and protocristid, and the metacone and lied with Cimolestes and `ùngulatomorphs'' talonid basin are reduced or absent.'' and Erinaceus (®g. 50A, C). Also, in Meng Beyond a super®cial resemblance in molar and Wyss (2001), Leptictis did not fall with outline, there is little dental evidence linking Zalambdalestes ϩ Barunlestes (®g. 48A, C). zalambdalestids and ``zalambdadonts''. Gregory and Simpson's (1926a: 14) orig- However, as discussed below under asioryc- inal claim that Zalambdalestes was a stem titheres, there are some features of the basi- ``zalambdadont'' has not been repeated by cranium that are shared between zalambda- any subsequent authors. Gregory and Simp- lestids, asioryctitheres, and some ``zalamb- son (1926a) did not clarify what they meant dadonts''. by ``zalambdadont'', although it seems likely WITH LAGOMORPHS,RODENTS, AND ELE- they were using it in the sense of Gill (1883), PHANT SHREWS: Van Valen (1964) allied za- who coined the term for mammals with lambdalestids with the early Tertiary Asian broad molars surmounted by W-shaped ridg- anagalids, pseudictopids, and eurymylids, es that he placed in the infraorder Zalamb- which he considered to be basal lagomorphs. dadonta containing Chrrsochloridae, Solen- His tentative phylogeny (ibid.: ®g. 3) depict- odontidae, and Tenrecidae. (Recent DNA se- ed pseudictopids (and anagalids) as the sister quence analyses do not support a monophy- group of lagomorphs, but in the text (ibid.: letic Lipotyphla with golden moles and 489) he suggested that Zalambdalestes may tenrecids separated from other lipotyphlans be closer to the rabbit clade, based on the in Afrotheria along with elephant shrews, si- shared `ènlargement of the lower medial in- renians, hyracoids, and proboscideans cisor . . . with the concomitant development [Springer et al., 1997; Stanhope et al., 1998; of diastemata in front of P2 and p3.'' Mc- Madsen et al., 2001].) As noted by Asher et Kenna (1975: 34) wrote that ``Zalambdales- al. (2002: 16), ``Gregory and Simpson tes is cladistically a Cretaceous lagomorph'', (1926) [1926a] did not provide an etymolog- and he included Zalambdalestidae and Du- 2004 WIBLE ET AL.: ZALAMBDALESTES 121 plicidentata as sister taxa along with Pseu- formula, but it is uncertain from which po- dictopidae in Lagomorpha. In support of the sition. Consequently, the enlarged incisor in zalambdalestid-duplicidentate relationship, Zalambdalestes (and Barunlestes) could be McKenna offered the enlargement of the ®rst either the ®rst or second from the ancestral lower incisor and the second upper incisor eutherian formula of four. However, Kul- (the I1 of this report). McKenna (1994: 57) beckia with four lower incisors, with the en- enumerated additional resemblances between larged one the ®rst, supports that the en- Barunlestes and the modern groups of lago- larged tooth in Zalambdalestes (and Barun- morphs (®g. 54): `àn enlarged pair of ante- lestes) as the i1. rior incisors accompanied by other, smaller To search for additional craniodental fea- rear incisors, a developing gap between the tures allying zalambdalestids with lago- incisors and the cheek-teeth, and inner enam- morphs, we compared our observations on el of the upper cheek-teeth that sometimes Zalambdalestes with the character lists and enters the tooth sockets.'' He also noted that distributions for gliriform mammals pub- the lower incisor of Barunlestes extends far lished in Novacek (1985, 1986a), Li and back in the jaw and has enamel that `ìs re- Ting (1985), Luckett (1985), Li et al. (1989), stricted to an outer U-shaped band of single- Dashzeveg et al. (1998), and Meng and Wyss layered enamel, like that of later lago- (2001). A number of derived features are morphs.'' As noted above, it is uncertain shared between zalambdalestids and lago- what specimen of Barunlestes provided Mc- morphs, but none are unique to the two Kenna with the observation on restricted groups. (1) Palatine size on the palate (No- enamel, and it may in fact be a new genus vacek, 1985) is subequal to or smaller than of eurymylid (see Fostowicz-Frelik and Kie- the premaxilla (also in rodents, dermopter- lan-Jaworowska, 2002). One of the features ans, and perhaps plesiadapiforms). (2) Orbit- McKenna reported for Barunlestes does not al exposure of the palatine (Novacek, 1985) occur in the MAE and CAE Zalambdalestes, is narrowed at the base of the orbital wall that is, there is no evidence of hypsodonty (also in rodents, leptictids, and plesiadapi- on the upper cheekteeth, which are well pre- forms) (see above; ®gs. 53±55). (3) Sphe- served in PSS-MAE 130. nopalatine foramen (Novacek, 1985) is at the Several authors have questioned the ho- maxillo-palatine suture (also in rodents, li- mologies of the enlarged lower incisor potyphlans, and perhaps anagalids) (®gs. 54, shared by Zalambdalestes and lagomorphs 55). (4) Ectopterygoid crest on the alisphe- (and rodents). Both Luckett (1985) and noid (Novacek, 1986a) is distinct (also in ro- Meng and Wyss (2001) have noted that the dents, macroscelidids, leptictids, archontans, tooth in question in lagomorphs (and ro- erinaceids, and asioryctitheres) (®gs. 53, 54, dents) is the retained deciduous second in- 56). (5) Dorsal exposure of the alisphenoid cisor (Moss-Salentijn, 1978; OoeÁ, 1980; in the orbital wall (Novacek, 1986a) is broad Luckett, 1985), whereas these authors scored (also in asioryctitheres, leptictids, and ro- the tooth in Zalambdalestes as the ®rst inci- dents) (®gs. 53, 54). (6) Internal carotid ar- sor. The recent report of four lower incisors tery (Novacek, 1985, 1986a) is medially po- in Kulbeckia (®g. 51C; Archibald et al., sitioned (also in asioryctitheres, metatheri- 2001; Archibald and Averianov, 2003) sup- ans, monotremes, and some rodents, xenar- ports the latter interpretation. The primitive thrans, chiropterans, ungulates, and eutherian formula included four lower inci- carnivorans, Wible, 1986). (7) Hypoglossal sors (Rougier et al., 1998; Ji et al., 2002), the foramina (Novacek, 1986a) are double (or condition found in Early Cretaceous Proken- triple) and closely spaced (also in rodents, nalestes (Sigogneau-Russell et al., 1992; per- metatherians, and Vincelestes, Rougier et al., sonal obs.) and Eomaia (Ji et al., 2002) and 1996). (8) Mandibular condyle (Novacek, in Late Cretaceous Asioryctes (Kielan-Ja- 1985, 1986a) is relatively high compared to worowska, 1975a) and Ukhaatherium (No- the toothrow (also in rodents, macroscelidids, vacek et al., 1997). Zalambdalestes (and Ba- lipotyphlans, archontans, and some xenar- runlestes) with a lower incisor count of three thrans and ungulates), although the condition (®g. 51A, B) has lost one from the ancestral in lagomorphs differs from Zalambdalestes 122 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 54. The skull and lower jaw of the lagomorph Prolagus sardus, a Quaternary ochotonid, in right lateral view, redrawn from Dawson (1969: ®gs. 2, 3, 6). Parallel lines indicate the cut surfaces of zygoma. Abbreviations: an, (mandibular) angle; as, alisphenoid; con, (mandibular) condyle; cor, coronoid process; e?, ethmoid?; eam, external acoustic meatus; ec, ectotympanic; ecpc, ectopterygoid crest; enpc, entopterygoid crest; fr, frontal; iof, infraorbital foramen; ma, mandible; mal, masseteric line; mf, mental foramina; mx, maxilla; mxfe, maxillary fenestra; na, nasal; opf, optic foramen; os, orbitosphenoid; pa, parietal; pal, palatine; pe, petrosal; pmx, premaxilla; spf, sphenopalatine foramen; sq, squamosal. in that the condylar process is the highest Meng et al., 1994; Shoshani and McKenna, process on the mandible (®gs. 53±55). In 1998; Dashzeveg et al., 1998; Meng and light of their known distributions, features 4, Wyss, 2001) not present in zalambdalestids. 5, and 7 above may in fact be primitive for Included on the list of cranial features uniting eutherians rather than being derived. Finally, lagomorphs and rodents in the superorder in lagomorphs as in Zalambdalestes and lep- Glires to the exclusion of zalambdalestids are tictids, the alisphenoid contacts the palatine (®gs. 54, 55): incisive foramina large; pre- (also in some rodents) (®gs. 53±55). How- maxilla-frontal contact; palatal exposure of ever, the lagomorph (and rodent) condition is the premaxilla and maxilla subequal; alisphe- not via a distinct anterior process that ex- noid canal present; accessory foramen ovale tends rostral to the optic foramen. present; sphenoidal foramina for the masse- Perusal of the above list reveals that all of teric and buccinator nerves present; glenoid the craniodental features that zalambdalestids fossa elongate with no postglenoid process; share with lagomorphs also occur in rodents, and auditory bulla formed by expanded ec- although no features are unique to rodents, totympanic. In light of the strong morpho- lagomorphs, and zalambdalestids. Lago- logical support for Glires, we consider lagomorphs and rodents share a remarkable num- morph af®nities for zalambdalestids as sup- ber of additional derived features (see No- ported by McKenna (1975, 1994) to be high- vacek, 1985, 1986a; Novacek, et al., 1988; ly unlikely. 2004 WIBLE ET AL.: ZALAMBDALESTES 123

Fig. 55. The skull and lower jaws of the rodent Cocomys lingchaensis, an early Eocene ctenodactyloid, in right lateral view. The skull is redrawn from Li et al. (1989: ®g. 2), and the lower jaw is from CM-VP 31369. Dashed lines represent broken surfaces. Abbreviations: as, alisphenoid; asc, alisphenoid canal; con, (mandibular) condyle; foa, foramen ovale accessories, fr, frontal; iof, infraorbital foramen; ip, interparietal; lac, lacrimal; M3, upper third molar; ma, mandible; maf, masseteric fossa; mx, maxilla; na, nasal; opf, optic foramen; os, orbitosphenoid; pa, parietal; pal, palatine; pe, petrosal; pgf, postglenoid foramen; pmx, premaxilla; sq, squamosal.

An alternative hypothesis is the placement many more relevant taxa in their phyloge- of zalambdalestids as an outgroup to the ex- netic analysis than did Archibald et al. tant orders Lagomorpha and Rodentia, as (2001), found no support for a zalambdales- supported recently by Archibald et al. (2001) tid-Glires clade (®g. 48A, C). Consequently, (®g. 49C). In a volume on the evolutionary we consider Glires af®nities for zalambda- relationships of rodents, Li and Ting (1985) lestids unlikely. and Luckett (1985) addressed the af®nities of A third hypothesis is inclusion of zalamb- Glires to zalambdalestids amongst other taxa. dalestids in a higher level clade including the These authors noted numerous shared de- extant orders Lagomorpha, Rodentia, and rived features from the dentition and skull Macroscelidea, suggested as a possibility by allying lagomorphs, rodents, eurymylids, and Novacek et al. (1988) and adopted by Mc- mimotonids, but virtually no support for al- Kenna and Bell (1997) as their emended An- lying these forms with either zalambdales- agalida (see also Shoshani and McKenna, tids, anagalids, or pseudictopids. A more re- 1998). Morphological support for the group- cent study of basal Glires by Dashzeveg et ing of these three extant orders is weak, with al. (1998) included Barunlestes, but that only three synapomorphies identi®ed to date form did not share a single derived state from (Novacek et al., 1988). One of these is a soft- the dentition and lower jaw with any other tissue feature concerning the orientation of taxon considered. Similarly, Meng and Wyss the embryonic disc toward the mesometrial (2001), who as discussed above considered pole of the uterus at implantation (Novacek 124 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 and Wyss, 1986a), which is not identi®able Nessov et al. (1998) have allied Zalambda- in fossils. The two hard-tissue features con- lestes with Asioryctes (®g. 46A, C), which is cern separate canals in the alisphenoid for known from the Barun Goyot Formation branches of the mandibular nerve, present in (Kielan-Jaworowska, 1975a) and perhaps lagomorphs, many rodents, and most ma- Ukhaa Tolgod (Dashzeveg et al., 1995). In croscelidids (Novacek and Wyss, 1986a), Archibald (1996) and Nessov et al. (1998), and perhaps anagalids (Shoshani and Mc- Zalambdalestes and Barunlestes are sister Kenna, 1998), and the course of the ramus taxa in a clade with Asioryctes, which is well inferior of the stapedial artery (and lesser pe- removed from Kennalestes, the other Late trosal nerve) dorsal to the tympanic roof, Cretaceous Mongolian eutherian considered present in lagomorphs, rodents, macrosceli- by these authors, which occurs in Bayn Dzak dids, some chiropterans, and possibly leptic- (Kielan-Jaworowska, 1969a) and Ukhaa Tol- tids (Novacek, 1986a; Wible, 1987; Novacek god (Dashzeveg et al., 1995). In Novacek et al., 1988; Wible and Davis, 2000). Za- (1997), Zalambdalestes, Asioryctes, and pla- lambdalestids do not have separate, well-de- centals form a trichotomy; the position of veloped canals for branches of the mandib- Kennalestes is not considered. Novacek et al. ular nerve, although there is a small, pre- (1997) named a new taxon Asioryctitheria to sumed nervous canal through the left ecto- include the asioryctids Asioryctes and pterygoid crest of PSS-MAE 130 (®g. 37B). Ukhaatherium plus Kennalestes. Based on Moreover, the zalambdalestid ramus inferior the presence of epipubics in Ukhaatherium runs in a groove on the tegmen tympani, ven- and Zalambdalestes along with several other tral to the tympanic roof (®g. 37D). Never- primitive features, Novacek et al. (1997) theless, zalambdalestids do exhibit a variant considered both asioryctitheres and zalamb- regarding the course of the rostral continua- dalestids to be basal eutherian lineages. Mc- tion of the ramus inferior, the ramus infraor- Kenna et al. (2000) tentatively referred Dau- bitalis. In the extant forms named above, ac- lestes nessovi from the Coniacian of Uzbek- cording to Wible (1987), the stapedial artery istan to Asioryctitheria. These authors noted passes through a foramen in the tympanic a general resemblance in the skull and den- roof and bifurcates into the ramus superior tition between Daulestes and asiorycitheres, and ramus inferior. The ramus inferior con- in particular Asioryctes and Ukhaatherium, tinues forward within the cranial cavity and but identi®ed few derived similarities beyond exits via one of three apertures: the piriform the position for the postglenoid foramen an- fenestra in lagomorphs, chiropterans, and terior to the postglenoid process, which in most rodents (Wible, 1987); an aperture in or fact is damaged in Daulestes. Finally, in Ji near the foramen ovale in macroscelidids et al. (2002) Zalambdalestes was united with (Bugge, 1972; MacPhee, 1981); or the con- the asioryctitheres Asiorcytes, Ukhaather- ¯uent superior orbital ®ssure/foramen rotun- ium, and Kennalestes (®g. 50A, C); Daules- dum in some bats (Kallen, 1977) and dipo- tes was not allied with these taxa, but with doid rodents (Bugge, 1971). The artery in za- ``ungulatomorphs'', Erinaceus, Cimolestes, lambdalestids in front of the ear region likely and Gypsonictops. followed a course like that in some bats and In light of the above phylogenetic hypoth- dipodoid rodents, dorsal to the sphenoid and eses, comparison of Zalambdalestes and into the orbit via the foramen rotundum (®gs. asioryctitheres seems warranted. The skull 37D, 44C). Rather than allying zalambdales- and dentition of Asioryctes and Kennalestes tids with any particular extant anagalidans, have been described in detail by Kielan-Ja- however, a course for the ramus inferior dor- worowska (1969a, 1975a, 1981), but a full sal to the sphenoid may support a zalamb- description of Ukhaatherium is still in prep- dalestid-asioryctithere clade or be primitive aration (Novacek et al., in prep.). In their re- for eutherians in that it is also probably the cent evaluation of deltatheridiid relation- condition in Vincelestes (Rougier et al., ships, Rougier et al. (1998) published some 1992). comparisons between zalambdalestids and WITH ASIORYCTITHERES: Recently pub- asioryctitheres, both in the text and data ma- lished cladograms in Archibald (1996) and trix. We expand on these comparisons here. 2004 WIBLE ET AL.: ZALAMBDALESTES 125

Fig. 56. The skull of Asioryctes nemegtensis (A) and Kennalestes gobiensis (B) in ventral view, redrawn from Kielan-Jaworwoska (1984c: ®g. 1). Abbreviations: ec, ectotympanic; ecpc, ectopterygoid process; egp, entoglenoid process; enpc, entopterygoid process; gf, glenoid fossa; I4, upper fourth incisor; I5, upper ®fth incisor; pf, piriform fenestra; pr, promontorium; ptc, posttympanic crest; tp, tympanic process of Kielan-Jaworowska (1981).

Zalambdalestes and asioryctitheres exhibit these, Kielan-Jaworowska (1984a: 115) not- the following primitive features not found ed the following primitive characters shared typically in more advanced eutherians: the by zalambdalestids, Kennalestes, and Asio- last upper incisor in the maxilla or in the pre- ryctes: ``the inclination of the occipital plate maxillary-maxillary suture (also known in upwards and forwards from the condyles; Kulbeckia) (®gs. 7, 51C±E, 56); the nasals posterior position of f. ovale; large promon- expanded broadly posteriorly contacting the torium; relatively posterior position of the lacrimals (also known in Kulbeckia and Ba- glenoid fossa, opposite the anterior half of runlestes) (®gs. 42, 51B±E); lacrimal tuber- the promontorium; long jugal, reaching back cle present (also known in Kulbeckia); pter- [sic] the glenoid fossa; medial position of the ygoids meet on the midline; glenoid fossa al- internal carotid artery; medial in¯ection of most entirely on the zygoma and not the the angular process of the dentary.'' Of these braincase proper (also known in Barunlestes) characters, we have noted above that the oc- (®gs. 4D, 43, 56); and epipubic bones present ciput is not inclined forwards and the angular (also known in Barunlestes). In addition to process is not medially in¯ected in Zalamb- 126 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 dalestes.SaÂnchez-Villagra and Smith (1997) pect of the glenoid fossa, whereas it buttress- have claimed that the angle is also not me- es the entire posterior aspect in asiorycti- dially in¯ected in Kennalestes and Asioryctes theres. The crista interfenestralis in Zalamb- (contra Kielan-Jaworowska, 1975a; Kielan- dalestes is a low-lying, delicate ridge, deeply Jaworowska et al., 1979), and Rougier et al. recessed from the caudal tympanic process of (1998: character 73) scored the angle as pos- the petrosal; in asioryctitheres it is much teriorly directed for these taxa. Additionally, stouter and higher, at roughly the same level we are uncertain of the polarity of one char- as the caudal tympanic process. Zalambda- acter on Kielan-Jaworowska's (1984a) list: lestes and Barunlestes also share with asio- the medial position of the internal carotid ar- ryctitheres a deep groove connecting the tery. In addition to Zalambdalestes and asio- sphenopalatine and maxillary foramina, dis- ryctitheres, a medial position of the internal tinct ectopterygoid and entopterygoid crests carotid is found in metatherians and mono- (®gs. 4D, 43, 56B), foramen ovale between tremes (Wible, 1986), but a lateral the alisphenoid and the squamosal; a supra- (transpromontorial) position occurs in the meatal foramen, a ¯at anteromedial ¯ange on prototribosphenidan Vincelestes (Rougier et the promontorium, and a posttympanic crest al., 1992), a petrosal from the Mongolian of the squamosal (®gs. 4D, 37A, C, 56). Za- Early Cretaceous tentatively referred to the lambdalestes and asioryctitheres share a basal eutherian Prokennalestes (Wible et al., common recess for the foramina transmitting 1997, 2001), and Daulestes (McKenna et al., the major palatine and caudal nasal nerves 2000). Rather than a primitive feature, a me- and vessels, mastoid foramina within the pedial position may be a derived trait poten- trosal bone, and a fusiform ectotympanic. tially allying zalambdalestids and asiorycti- Two mastoid foramina have been described theres. for Asioryctes by Kielan-Jaworowska (1981: Zalambdalestes and asioryctitheres also ®g. 2), with the position of the upper one share some features that are of somewhat reminiscent of those in Zalambdalestes (®g. limited distribution among eutherians. In 40). A single, more laterally placed mastoid fact, Zalambdalestes exhibits several features foramen was reported for Kennalestes (Kie- that Novacek et al. (1997) employed in their lan-Jaworowska, 1981: ®g. 5). Mastoid fo- diagnosis of Asioryctitheria: the position of ramina within the petrosal are unusual the postglenoid foramen in front of rather among mammals, although they have also than behind the postglenoid buttress (also been reported for the basal metatherians Pu- known in Barunlestes); the postglenoid pro- cadelphys (Marshall and Muizon, 1995: ®g. cess continuous with the entoglenoid process 18) and Mayulestes (Muizon, 1998: ®g. 9) in (also known in Barunlestes) (®gs. 4D, 37A, positions like those in Zalambdalestes and C, 56A); a ®ngerlike tympanic process be- Asioryctes. The fusiform ectotympanic of hind the fenestra cochleae connected to the Zalambdalestes and asioryctitheres is unusu- promontorium via a distinct crista interfenes- al in that the expansion is lateral, supporting tralis (also known in Kulbeckia and Barun- the external acoustic meatus, rather than me- lestes) (®gs. 37C, 56B); and a large piriform dial in the bullar ¯oor (®gs. 37C, 56). In ad- fenestra in the anterior roof of the middle ear dition, in Zalambdalestes and Ukhaatherium, (also known in Barunlestes) (®gs. 4D, 37A, the anterior crus of the ectotympanic contacts B, 56A). In fact, the resemblance in the last the entoglenoid process. This also appears to of these features is perhaps even more un- be the case in Kennalestes (see Kielan-Ja- usual in that the piriform fenestra apparently worowska, 1981: ®g. 6). transmitted the ramus inferior of the stapedial Novacek et al. (1997) have already com- artery in both Zalambdalestes and Asioryctes mented that some of the features supporting (Kielan-Jaworowska, 1981). However, we Asioryctitheria (and allying it with Zalamb- add that there are differences in the degree dalestes) are similar to those occurring in of development of two of these features, the some lipotyphlan insectivorans. Rare among postglenoid process and the crista interfenes- placentals, entoglenoid processes are widely tralis. In Zalambdalestes, the postglenoid distributed among lipotyphlans (McDowell, process borders only the posteromedial as- 1958; MacPhee, 1981; MacPhee et al., 2004 WIBLE ET AL.: ZALAMBDALESTES 127

Fig. 57. The skull and lower jaw of the tenrecid Potamogale velox CM 40781 in right lateral view (reversed from the original). Dashed line is suture between frontal and parietal, which is drawn based on CM 16034. Abbreviations: an, (mandibular) angle; as, alisphenoid; asc, alisphenoid canal; bs, basisphenoid; con, (mandibular) condyle; cor, coronoid process; ec, ectotympanic; enpc, entopterygoid crest; fr, frontal; iof, infraorbital foramen; m3, lower third molar; ma, mandible; mx, maxilla; na, nasal; os, orbitosphenoid; pa, parietal; pal, palatine; pe, petrosal; pmx, premaxilla; sq, squamosal; ssf, subsquamosal foramen.

1988), although they are lacking in Eocene 1988: ®g. 4A) in which the foramen is an- forms such as Diacodon, the dormaalid Mac- terior to the process. Many lipotyphlans also rocranion, and the amphilemurid Pholido- have a fusiform ectotympanic reminiscent of cercus (MacPhee et al., 1988). According to the element in Zalambdalestes and asioryc- MacPhee (1981) and MacPhee et al. (1988), titheres with the expansion ¯ooring the ex- the entoglenoid process is enlarged in ten- ternal acoustic meatus and not the middle ear recs, Solenodon, and some erinaceids (e.g., (®g. 58; for examples, see illustrations in Echinosorex), but is barely evident in sori- MacPhee et al., 1988; Frost et al., 1991). In- cids and other erinaceids (e.g., some Erina- terestingly, the anterior crus of the ectotym- ceus). However, the lipotyplan entoglenoid panic in some extant lipotyphlans contacts process is a rather con®ned, stubby process the entoglenoid process (e.g., Parechinus, (®g. 58) and not a thin, elongate ridge con- CM 45275, ®g. 58; Potamogale, CM 40781; tinuous with a better developed postglenoid Solenodon, CM 18069). Another resem- process as in Zalambdalestes, Barunlestes, blance is a ®ngerlike tympanic process con- and asioryctitheres. Moreover, the postgle- nected with the promontorium via a crista in- noid foramen lies posterior to the entogle- terfenestralis, which occurs in some extant noid process in most lipotyphlans and not an- erinaceids and tenrecids (MacPhee, 1981). A terior as in the Mongolian Late Cretaceous low tympanic process is illustrated for the taxa. The exception to this is in some eri- Eocene erinaceomorphs Diacodon, Macro- naceids (e.g., Hemiechinus, MacPhee et al., cranion, and Pholidocercus by MacPhee et 128 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

Fig. 58. The skull and lower jaw of the erinaceid Parechinus aethiopicus CM 45275 in lateral view. Abbreviations: an, (mandibular) angle; as, alisphenoid; asc, alisphenoid canal; bs, basisphenoid; con, (mandibular) condyle; cor, coronoid process; ec, ectotympanic; ecpc, ectopterygoic process; egp, entoglenoid process; enpc, entopterygoid crest; fr, frontal; ip, interparietal; ju, jugal, ma, mandible; mx, maxilla; na, nasal; os, orbitosphenoid; pa, parietal; pal, palatine; pe, petrosal; pgf, postglenoid process; pgp, postglenoid process; pmx, premaxilla; sq, squamosal. al. (1988: ®gs. 6, 10A, 11). However, there (e.g., rodents, Wahlert, 1974; ungulates, is a major distinction in the crests forming Thewissen, 1990). Lastly, an ectopterygoid the posterior wall of the middle ear: in Za- crest of the alisphenoid is present in erina- lambdalestes and asioryctitheres, the caudal ceids (®g. 58), but also in various other pla- tympanic process forms a continuous wall centals (e.g., tree shrews, elephant shrews, behind the stapedius fossa (from the tympan- Novacek, 1986a). ic process to the stylomastoid notch), but In addition to the resemblances noted such a wall is entirely lacking in the lipo- above, there is a long list of differences be- typhlans (MacPhee, 1981; MacPhee et al., tween Zalambdalestes and asioryctitheres. 1988). A large piriform fenestra is found in Kielan-Jaworowska (1984a: 115) noted the tenrecids and soricids (McDowell, 1958; following for zalambdalestids: ``in addition MacPhee, 1981) and perhaps Diacodon to the differences in the dentition: greater (MacPhee et al., 1988: ®g. 11), but it does size, a more elongated and tubular snout, a not tramsmit the ramus inferior. Moreover, relatively shorter mesocranial region, a rela- large piriform fenestrae occur in Early Ter- tively more expanded brain case, the pres- tiary members of various placental lineages ence of a large posterior [minor] palatine fo- 2004 WIBLE ET AL.: ZALAMBDALESTES 129 ramen, the presence of a median process of therians is in order. Arguing against closer the presphenoid [?parasphenoid] . . . the ab- af®nities between zalambdalestids and zhe- sence of a basisphenoid wing, the presence lestids than between zalambdalestids and of f. rotundum (which in Asioryctes in [sic] asioryctitheres is the structure of isolated pe- con¯uent with sphenorbital ®ssure).'' To trosals that Archibald et al. (2001) have re- these, we add the following. The maxilla ferred to various zhelestids, including Para- contributes to the medial orbital wall in zhelestes and Eoungulatum. These petrosals asioryctitheres, but not in zalambdalestids. do not show the unique features shared by Zalambdalestes has a posterior opening to zalambdalestids and asioryctitheres, includ- the posttemporal canal, lacking in asioryc- ing the crista interfenestralis connected to the titheres. There is only one subsquamosal fo- caudal tympanic process of the petrosal and ramen in Zalambdalestes, but multiple ones the ®ngerlike tympanic process. Moreover, in asioryctitheres. Finally, there is a single these petrosals have a short, vertical prootic hypoglossal foramen in asioryctitheres, but canal like that described by Wible et al. two or three in zalambdalestids. In addition (2001) in Prokennalestes. to these cranial differences are numerous postcranial differences between Zalambda- lestes and asioryctitheres, with some of the CONCLUSIONS specializations in the former more reminis- In conjunction with the studies of Gregory cent of those in placentals (Kielan-Jawo- and Simpson (1926a), Simpson (1928a, rowska, 1977, 1978; Horovitz et al., 1998; 1928b), Kielan-Jaworowska (1969a, 1981, Horovitz, 2000). 1984a, 1984b, 1984c, 1986), and Crompton WITH ZHELESTIDS: Novacek et al. (2000) and Kielan-Jaworowska (1978), our descrip- described a new Late Cretaceous Mongolian tions of the MAE specimens recently col- eutherian from the Red Rum (Kholbot) lo- lected from the Djadokhta Formation and cality, near Ukhaa Tolgod, based on a left equivalents have made Zalambdalestes the maxillary fragment containing the ?deciduous P4, M1, and erupting M2. The bunodont most completely known Late Cretaceous the- teeth are reminiscent of those of zhelestids, rian from the standpoint of cranial morphol- in particular Parazhelestes and Eoungulatum, ogy, including the disposition of the major from the Coniacian of Uzbekistan and con- cranial nerves, arteries, and veins. The only trast with the sectorial teeth of asioryctitheres parts of the skull not yet described are the and zalambdalestids. The only other mammal nasal cavity and endocranial ¯oor, and we from Red Rum is a zalambdalestid, repre- hope to remedy this in the future through the sented by two damaged skulls and several study of high-resolution CT scans. fragmentary jaws and postcrania. The broad Recent phylogenetic analyses (e.g., Archi- dimensions of the heavily worn cheekteeth bald, 1996; Nessov et al., 1998; Rougier et on the skulls closely resemble those of the al., 1998; Ji et al., 2002), including our new maxillary fragment, suggesting that it amendments to the published matrices based also is a new taxon of zalambdalestid. If this on the new specimens described herein, have is the case, then the possibility exists that za- con®rmed the eutherian identity of Zalamb- lambdalestids and zhelestids are closely re- dalestes accepted by previous authors. Also lated. This also implies that zalambdalestids con®rmed are the close phylogenetic rela- are closely related to ungulates, if Archi- tionships of Zalambdalestes and Barunlestes bald's (1996) and others hypothesis of zhe- from the slightly younger Mongolian Barun lestid-ungulate af®nities is correct. Goyot Formation (see Archibald, 1996; Nes- Novacek et al.'s (2000) hypothesis of za- sov et al., 1998; Archibald et al., 2001; and lambdalestid-zhelestid af®nities has not been our amendments) and of these taxa with Kul- supported in any of the recent phylogenetic beckia from the late Turonian and Coniacian analyses (®gs. 46, 47, 49, 50). Nevertheless, of Uzbekistan (Archibald et al., 2001; and once these new specimens from Red Rum our amendments). However, no phylogenetic have been described, then testing the af®ni- analyses published to date include suf®cient ties of all the Mongolian Late Cretaceous eu- taxonomic and morphological breadth to as- 130 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 sess the broader relationships of these three tween the alisphenoid and squamosal; a su- zalambdalestid taxa. prameatal foramen; a medially positioned in- Our studies have revealed a number of ternal carotid artery; and mastoid foramina primitive features of the skull of Zalambda- entirely within the petrosal bone. In light of lestes, which viewed in the context of the these unusual similarities, we think that a za- recently reported epipubic bones in this tax- lambdalestid-asioryctithere clade is the most on (Novacek et al., 1997), support a position reasonable working hypothesis for these for zalambdalestids within Eutheria outside forms (see Ji et al., 2002). Endemic Asian of extant placentals (Novacek, 1997). Includ- clades from the Late Cretaceous have also ed among the primitive cranial features of been reported for multituberculates (Rougier Zalambdalestes are: the last upper incisor in et al., 1997; Kielan-Jaworowska and Hurum, the maxilla; nasals expanded posteriorly to 1997), squamates (Gao and Norell, 2000), contact the lacrimals; double lacrimal foram- and dinosaurs (Currie, 2000; Sereno, 2000). ina; pterygoids meeting on the midline; jugal Testing of the zalambdalestid-asioryctithere extending posteriorly to the glenoid process; hypothesis awaits broadscale phylogenetic and a relatively posterior position of the analysis, a goal of our future research. Inter- glenoid fossa, opposite the anterior half of estingly, some of the unusual characters of the promontorium of the petrosal, almost en- the ear region shared by zalambdalestids and tirely on the zygoma and not the braincase asioryctitheres are reminiscent of features proper. This evidence contraverts the few occurring in various lipotyphlans (e.g., ten- craniodental apomorphies that have been cit- recids, solenodontids, and erinaceids), the ed as allying Zalambdalestes with certain most notable exception being the medially placentals, such as lagomorphs (McKenna, positioned internal carotid artery. Extensive 1994) and Glires (Archibald et al., 2001). testing is needed in order to assess the pos- Along with these primitive features, Za- sibility of a close phylogenetic relationship lambdalestes exhibits numerous cranial spe- between the Mongolian Cretaceous eutheri- cializations. As noted by Kielan-Jaworowska ans and lipotyphlans. If such a relationship (1975a, 1984a), Kielan-Jaworowska and Tro- existed, epipubic bones might have been lost ®mov (1980), Archibald (1996), and Archi- independently and other postcranial special- bald et al. (2001), the taxon with which Za- izations (Kielan-Jaworowska, 1977, 1978; lambdalestes shares the most craniodental Horovitz, 2000) convergently acquired in apomorphies is the other well-known Mon- (some?) lipotyphlans and other placentals. golian zalambdalestid Barunlestes. These As reported by us previously (Wible et al., taxa share fewer specializations with the old- 1998), the current sample of partial and com- er zalambdalestid Kulbeckia (Archibald et plete crania referred to Zalambdalestes lechei al., 2001; Archibald and Averianov, 2003). exhibits a striking degree of individual vari- Beyond Zalambdalestidae, the clade with ation. Included among the variable features which Zalambdalestes shares the most cra- are: the presence/absence of a third incisor in nial specializations is the Mongolian Late the maxilla, P1, and p2; the degree of devel- Cretaceous Asioryctitheria. Included among opment of the postpalatine torus; and the po- these features are: the postglenoid foramen sition and number of the major palatine fo- in front of rather than behind the postglenoid ramina. Despite this variability, we have cho- process; the postglenoid and entoglenoid sen for now to retain all individuals in one processes continuous; a fusiform ectotym- species. However, we add that the entire panic expanded dorsolaterally beneath the sample of Z. lechei (CAE, ZPAL, PIN, and external acoustic meatus and contacting the MAE) should be restudied to assess the pos- entoglenoid process; a ®ngerlike tympanic sibility that more than one taxon is repre- process posterior to the fenestra cochleae sented. connected via a distinct crista interfenestralis to the promontorium; a large piriform fenes- ACKNOWLEDGMENTS tra in the anterior roof of the middle ear, which transmitted the ramus inferior of the We are grateful to Zo®a Kielan-Jaworow- stapedial artery; foramen ovale situated be- ska for access to Cretaceous therian mam- 2004 WIBLE ET AL.: ZALAMBDALESTES 131 mals collected by the Polish±Mongolian of carnivorous marsupials, and af®nities of the Expeditions housed with the Institute of insectivorous peramelids. Zoological Journal of Paleobiology in Warsaw, and for her enthu- the Linnean Society 59: 217±322. Archibald, J.D. 1982. A study of Mammalia and siastic support and interest as well as many geology across the Cretaceous-Tertiary bound- lively discussions on Mesozoic mammals. ary in Gar®eld County, Montana. University of We also thank Thomas Martin for discus- California Publication in Geological Sciences sions on incisor enamel in the MAE spec- 122: 1±286. imens of Zalambdalestes, and Dave Archi- Archibald, J.D. 1996. Fossil evidence for a Late bald and Robert Asher for access to unpub- Cretaceous origin of ``hoofed'' mammals. Sci- lished manuscripts. We also are grateful to ence 272: 1150±1153. Yaoming Hu, the American Museum of Archibald, J.D., and A.O. Averianov. 2003. The Late Cretaceous placental mammal Kulbeckia. Natural History, for unpublished observa- Journal of Vertebrate Paleontology 23: 404± tions, Rich Cifelli, Oklahoma Museum of 419. Natural History, for access to Montanales- Archibald, J.D., A.O. Averianov, and E.G. Ek- tes, and Mary Dawson, Section of Verte- dale. 2001. Late Cretaceous relatives of rabbits, brate Paleontology, Carnegie Museum of rodents, and other extant eutherian mammals. Natural History, for access to the mandible Nature 414: 62±65. of Cocomys illustrated in ®gure 55 and for Asher, R.J., M.C. McKenna, R.J. Emry, A.R. Ta- brum, and D.G. Kron. 2002. Morphology and discussions on Glires. We thank Timothy relationships of Apternodus and other extinct Rowe, Richard Ketcham, and Matthew zalambdadont, placental mammals. Bulletin of Colbert of the High Resolution X-ray Com- the American Museum of Natural History 273: puted Tomography Facility at the Depart- 1±117. ment of Geological Sciences of the Uni- Averianov, A.O. 1997. New Late Cretaceous versity of Texas at Austin. The skillful mammals of southern Kazakhstan. Acta Pa- preparation by Amy Davidson, AMNH, has laeontologica Polonica 42: 243±256. made our descriptions of these remarkable Averianov, A.O. 2000. Mammals from the Me- sozoic of Kirgizstan, Uzbekistan, Kazakhstan specimens possible. Three illustrators have and Tadzhikistan. In M.J. Benton, M.A. Shish- participated in the completion of the ®g- kin, D.M. Unwin, and E.N. Kurochkin (edi- ures. Ed Heck, AMNH (all photographs ex- tors), The age of dinosaurs in Russia and Mon- cept ®gure 40 and accompanying line golia: 627±652. Cambridge: Cambridge Uni- drawings except that with ®gure 23; and versity Press. ®gure 44); Gina Scanlon, CMNH (®gures Averianov, A., and L. Nessov. 1995. A new Cre- 4±6, 16, 23, 42, 43, and 45±58, plus ®nal taceous mammal from the Campanian of Ka- zakhstan. Neues Jahrbuch fuÈr Geologie und Pa- labeling and layout); and Mark Klingler, laÈontologie, Monatshefte 1995: 65±74. CMNH (®gures 7, 9, 10, and 37). We also Bazhanov, V.S. 1972. First Mesozoic Mammalia thank T.J. Gaudin and I. Horovitz for re- (Beleutinus orlovi Bazhanov) from the USSR. view of the manuscript and discussion of Teriologiya 1: 74±80. 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ADDENDUM At the ®nal submission of our manuscript, we are only distantly related to Glires. In the pre- became aware of a major monographic treatment ferred tree of Meng et al. (2003), with all char- of the basal gliroid mammal Rhombomylus by acters unordered, the sister group of Glires is a Meng et al. (2003; see References). These authors clade consisting of Anagale, Anagalopsis, and include a broadscale phylogenetic analysis with a Pseudictops. The Mongolian Late Cretaceous eu- matrix composed of 227 dental, cranial, and post- therians are at the base of the tree, with Kenna- lestes and Asioryctes as successive outgroups to a cranial characters across 50 terminal taxa, includ- monophyletic Zalambdalestidae composed of Za- ing the Mongolian Late Cretaceous eutherians Za- lambdalestes and Barunlestes. With the editor's lambdalestes, Barunlestes, Asioryctes, and Ken- permission, we have not attempted to address nalestes. Contra Archibald et al. (2001), in all an- Meng et al.'s (2003) analysis here, but will do so alyzes by Meng et al. (2003), the zalambdalestids in subsequent publications. 2004 WIBLE ET AL.: ZALAMBDALESTES 141

APPENDIX 1 LIST OF ANATOMICAL TERMS On the left are the terms used here; on the right are references and/or Nomina Anatomica Veterinaria (NAV) equivalents. 142 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

APPENDIX 1 (Continued) 2004 WIBLE ET AL.: ZALAMBDALESTES 143

APPENDIX 1 (Continued) 144 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281

APPENDIX 1 (Continued)