AMERICAN MUSEUM Novitates PUBLISHED by the AMERICAN MUSEUM of NATURAL HISTORY CENTRAL PARK WEST at 79TH STREET, NEW YORK, N.Y

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AMERICAN MUSEUM Novitates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 2780, pp. 1-17, figs. 1-8, table 1 February 8, 1984

Prosarcodon lonanensis, a New Paleocene Micropternodontid Palaeoryctoid Insectivore from Asia

MALCOLM C. MCKENNA,1 XUE XIANGXU,2 AND ZHOU MINGZHEN3

ABSTRACT

A new genus and species of primitive microp- currence of the micropternodontids prior to their temodontid soricomorph insectivores, Prosarco- apparent restriction to North America. The pe- don lonanensis, is described from the Paleocene trosal bone of Prosarcodon is similar to that of Fangou Formation, Shaanxi Province, People's Palaeoryctes puercensis from the North American Republic of China. Prosarcodon lonanensis sheds Paleocene. Prosarcodon and Sarcodon were both new light on the origin of the mammalian family specialized in the loss ofa molar, unlike the youn- Micropternodontidae, linking them to the Palaeo- ger genus Sinosinopa from Inner Mongolia (Nei ryctoidea and demonstrating an early Asian oc- Mongol), PRC.

INTRODUCTION Among collections of Chinese Paleogene ious anagalids from the Chinese Paleogene, mammalian fossils there are 17 species of the earliest previous records ofChinese fossil insectivores (sensu lato) from various strati- insectivores are Sarcodon from the upper Pa- graphic levels at more than a dozen major leocene or lower Eocene of North China and localities. Most of them are erinaceids from the MPR and Hyracolestes from the upper the Oligocene. Thus far, Cretaceous insecti- Paleocene or lower Eocene of the MPR and vores and insectivore-like animals such as the upper Paleocene ofAnhui Province, PRC. Prokennalestes, Kennalestes, Asioryctes, Za- The affinities of most of the early non-eri- lambdalestes, Barunlestes, Deltatheridium, naceoid insectivores of Asia have been dis- Deltatheroides, and Hyotheridium have not puted in one way or another. Sarcodon is no been found in China although they occur exception. With the description of Prosar- nearby to the north in the Mongolian Peo- codon, presented here, we hope to throw some ple's Republic (MPR). Except Endotherium much-needed light on the relationships of from the Chinese Lower Cretaceous and var- Sarcodon, Sinosinopa, Palaeoryctes, and the ' Frick Curator, Department of Vertebrate Paleontology, American Museum of Natural History. 2 Instructor, Department of Geology, Northwest University, Xian, Shaanxi, PRC. 3Research Professor, Institute of Vertebrate Paleontology and Paleoanthropology, Academia Sinica, Beijing, PRC.

FIG. 1. Map of Shaanxi Province, PRC, showing location of Xian, Lonan, and Shimen.

peculiar "American" insectivore family Mi- ulated jaws of a Sarcodon-like insectivoran cropternodontidae. was discovered by Xue and technician Zhao In 1977 fossil mammals were found (Xue, Jufa in deposits of early or middle Paleocene 1978) and in 1978 a small skull with artic- age in the lower part of the Fangou Forma- 1 984 MCKENNA, XUE, AND ZHOU: PROSARCODON LONANENSIS 3 tion, Fangou Valley, near Shimen Commune, Pleistocene Lonan County, Shaanxi Province, PRC (fig. 1). The Shimen Basin is small, fault-bound- 2 _0 0 0 0 ed, and was formed in Sinian (Precambrian) E o .o. 220- quartzites and marbles during the early Ter- tiary. The basin is only about 52 km.2 in area and is about 110 km. east of Xian (170 km. 0 00 z 0000 t0| o 0 20 by road), about 15 km. north from Lonan, -00 00_ 200 capital city ofLonan County, in the northern CD0 W part of the Qinling Range at its boundary 0 with the North China Platform. Many other o 0L2 0 o small fault-controlled basins exist in the o -0-0-. i Qinling Range. The Shimen Basin contains three Cenozoic 1 z o co 0 rock units above its Sinian basement (Xue 0.0 and Jufa, 1982): w

Pleistocene Alluvium and 0. talus ____ . 40 Fm. Upper Miocene Gedamiao Red clay, con- o 000LFB. 120- or Pliocene (68 m.) glomerate, with Hippari- z on, etc. 0. Lower or middle Fangou Fm. Brown-red, sandy Paleocene (165 m.) mudstone

Precambrian Gaushanhe Fm. Quartzite and marble 0- o o -- The Fangou Formation is about 165 m. thick (fig. 2) and is unconformable both with ______the underlying Precambrian basement and 00

with the overlying Neogene Gedamiao For- o o o O 60 mation. The Fangou Formation is distrib- uted widely in the Shimen Basin and consists ofbrown-red, dense, sandy mudstones. These mudstones contain green deoxidation spheres oo oH C and are cut by a network ofinclined fractures filled with gypsiferous material. The Fangou Formation can be divided informally into upper and lower parts: the mudstones of the upper part (41 m.) of the Fangou Formation are interlayered with several gray-green conglomeratic sandy mudstones and silty sand- stones containing many calcareous concre- tions about 2 cm. in diameter. The lower part (124 m.) of the Fangou Formation contains FIG. 2. Generalized geological section of Ter- tiary deposits of the Shimen Basin, Shaanxi, PRC. several thin conglomeratic layers in the mid- LFB-lower fossiliferous beds where Prosarcodon dle and a thick one at the base. lonanensis and other Paleocene mammals were There are two fossil-bearing beds in the found (lower circle with cross). UFB-upper fos- Fangou Formation. One specimen of a bem- siliferous beds where one specimen of a bema- alambdid pantodont has been collected from lambdid pantodont has been recovered (upper cir- the upper fossil-bearing beds about 6 m. above cle with cross). Scale in meters. 4 AMERICAN MUSEUM NOVITATES NO. 2780 the base ofthe upper part ofthe Fangou For- chen" becomes "Zhou Mingzhen," etc. Also, mation, but the remaining fossils collected unless quoted from previous usage, Chinese thus far were found about 6 m. below the top family names ofauthors are listed before giv- of the lower part of the Fangou Formation, en names and are not separated by a comma where specimens of the anagalid genus Lin- from given names. nania, bemalambdid pantodonts, and the mesonychid Hukoutherium occur in addition ACKNOWLEDGMENTS to the palaeoryctoid Prosarcodon lonanensis. We thank Drs. Zhai Renjie of the IVPP, In both lithostratigraphy and fauna, as well and M. R. Dawson, M. J. Novacek, P. V. as geological structure, the Shimen Basin is Rich, and L. Van Valen for advice and other very similar to the Nanxiong Basin ofGuang- aid, Mr. Zhao Jufa for aid in the field, and dong Province in South China. The Fangou the IVPP staff for a cast ofthe type specimen Formation can be compared favorably with of Sinosinopa sinensis. Dr. R. J. Emry per- the Shanghu Formation of the Nanxiong Ba- mitted us to study the type specimen ofKen- sin. The two fossiliferous beds in the Fangou trogomphios strophensis and Dr. Dawson gave Formation are older than the dated parts of us access to various specimens in her care. the Taizichun Formation ofXinjian or ofthe Preparation of the type specimen of Prosar- Loumugeng Formation of Nei Mongol, PRC codon lonanensis was skillfully executed by (Inner Mongolia). Zhao Jufa and Otto Simonis. The illustra- The specimen from the Fangou Formation, tions were prepared by Messrs. Chester Tarka here made the type of Prosarcodon lonanen- and Raymond Gooris. This project was sup- sis, is poorly preserved and dorsally incom- ported in large part by a grant to Xue from plete, but the jaws and dentition remain gen- the Geological Academia Sinica for fieldwork erally in excellent condition and part of the and travel, partly by the American Museum basicranium is still present. The animal is, as of Natural History, partly by the Carnegie would be expected, somewhat more primi- Museum ofNatural History, and, with regard tive than Sarcodon. to travel expenses, partly by a U.S. National Science Foundation grant to Dr. R. M. Hunt at the University of Nebraska. INSTITUTIONAL ABBREVIATIONS AND ORTHOGRAPHY ORDER SORICOMORPHA GREGORY, 1910; MCKENNA, 1975 AMNH, American Museum of Natural History, New York, New York. SUPERFAMILY PALAEORYCTOIDEA WINGE, CMNH, Carnegie Museum of Natural History, 1917; VAN VALEN, 1963 Pittsburgh, Pennsylvania. FAMILY MICROPTERNODONTIDAE STIRTON IVPP, Institute of Vertebrate Paleontology and AND RENSBERGER, 1964 Paleoanthropology, Academia Sinica, Beijing, PRC. (=MICROPTERNODIDAE STIRTON MPR, Mongolian People's Republic. AND RENSBERGER, 1964; PRC, People's Republic of China. MICROPTERNODONTIDAE VAN VALEN, 1965; UM, University of Michigan Museum of Paleon- MICROPTERNODONTINAE VAN VALEN, 1966) tology, Ann Arbor, Michigan. USA, United States of America. PROSARCODON MCKENNA, XUE, USNM, National Museum of Natural History, AND ZHOU, NEW GENUS Smithsonian Institution, Washington, D.C. 20560. TYPE: Prosarcodon lonanensis McKenna, WNUG, Department ofGeology, Northwest Uni- versity, Xian, Shaanxi, PRC. Xue, and Zhou, new species. LOCALITY, ASSOCIATED FAUNA, AGE, AND Except where quoted from previous usage, DISTRIBUTION: As for the type species. all names from the Chinese language (Man- ETYMOLOGY: Pro, first, early, in allusion to darin, Beijing Dialect) are rendered here in the supposed ancestral position of this genus English in the current version ofPinyin. Thus, with regard to Sarcodon. Sarcodon, name of "Fan-gou" becomes "Fangou," "Chow Min- a latest Paleocene or earliest Eocene genus of 1984 MCKENNA, XUE, AND ZHOU: PROSARCODON LONANENSIS 5

Mongolian and Chinese fossil soricomorph tooth, but it lacks any sort of a cutting crest insectivores. on its posterior side and is therefore oval DIAGNOSIS: As for the type species. rather than triangular in cross-section. P' (or dP') is a small, single-rooted, pierc- Prosarcodon lonanensis McKenna, ing tooth that tilts forward slightly. Its rear Xue, and Zhou, new species slope is crested, as in Sinosinopa sinensis. Figures 3-7 Following a short diastema behind PI, the upper dentition (figs. 3, 4) is continuous TYPE: WNUG specimen no. 78ShOO 1, through M2. p2 is a double-rooted, piercing fragmentary skull and jaws. tooth about twice the size of P'. It too has a LOCALITY: Fangou Formation, Fangou posterior crest, which curves to join the para- Valley, Qinling Mountains, Shimen Com- style of P3. There is a faint heel at the rear mune, Lonan County, Shaanxi Province, andjust a trace ofa lingual cingulum running PRC. forward from it. ASSOCIATED FAUNA: Bemalambdidae, new .P3 is three-rooted and serves as a cutting genus and species; Hukoutherium, new blade as in Sinosinopa sinensis and the three species; and Linnania, new species. valid species of Micropternodus. The roots AGE: Early or middle Paleocene, Bema- lie dorsal to the parastyle, protocone, and lambda Zone. posterior cutting edge, respectively. The DISTRIBUTION: Type locality only. parastyle is low, but it projects far anteriorly. ETYMOLOGY: lonanensis-from Lonan City From the parastyle to the paracone apex the and County, Shaanxi Province, PRC. anterior crest is dull, but from the paracone DIAGNOSIS: Smaller than Sarcodon pyg- apex to the metastyle a concave and "hollow maeus from the Gashato and Naran Bulak ground" crest is present. No trace of a meta- localities ofthe MPR and from the Nomogen cone is seen. The protocone, although worn, locality ofNei Mongol, PRC. As in Sarcodon projects abruptly linguad at the lingual base pygmaeus (Szalay and McKenna, 1971, fig. of the tooth. A tiny apex was present before 11), P4 of Prosarcodon lonanensis does not wear. have its hypoconal shelf so well-developed P4 is broken across the lingual base of the as in Sinosinopa sinensis from the Arshanto paracone, but can be seen in its entirety and Formation of Nei Mongol and on the shelf reconstructed in spite of a gap separating the lacks the small hypoconal emminence of P4 protocone from the rest ofthe tooth. P4 lacks of Sinosinopa sinensis. Only MI possesses a a metacone and is three-rooted and trans- hypoconal shelf with a distinct hypocone. verse. In contrast to P3, P4 is a large tooth, Hypocone of MI less posterolingually ex- with the paracone towering above the cusps panded and paracone and metacone less of all other teeth. An external cingulum runs closely associated than in Sarcodon pyg- along the labial base ofthe paracone from the maeus. MI of Prosarcodon lonanensis differs anterior-projecting parastyle posteriad tojust from MI of Sarcodon pygmaeus by possess- behind the middle ofthe paracone base, where ing a faint anterior cingulum at the base of a suggestion of a stylar cusp deflects the cin- the protocone. Prosarcodon lonanensis (as gulum ventrad. The cingulum then continues well as Sarcodon pygmaeus) differs from Si- more or less straight back to the metastyle nosinopa sinensis by loss ofboth M3 and M3. but supports faint swellings that again suggest DESCRIPTION: There are three upper inci- stylar cusps. In the metastylar area the cin- sors per premaxilla (however, one incisor is gulum swings linguad to join the posterior not preserved in the present specimen). The cutting crest ofthe paracone. This last is steep, anteriormost upper incisor is the largest. All sharp, and "hollow-ground" as in P3. No trace upper incisors are rounded in cross-section of a metacone appears. The protocone is a and possess bluntly conical apexes. We ar- high cusp, although it is not so high as on bitrarily regard the upper incisors as per- M'. It is larger than that ofM2, however. The manent ones. protocone bears no anterior cingulum, but a The upper canine (presumably a perma- faint posterior cingulum begins at the pos- nent tooth) is a conical, curved, projecting terolingual base of the protocone and then 6 AMERICAN MUSEUM NOVITATES NO. 2780

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FIG. 3. Prosarcodon lonanensis McKenna, Xue, and Zhou, new genus and species. Northwest Uni- versity, Xian, PRC, specimen no. 78ShOO1, lower or middle Paleocene, Fangou Formation, Shimen Basin, Shaanxi Province, PRC. Buccal view of right maxilla and lowerjaw. Stereoscopic pair. See 5 mm. bar for scale.

merges with the posterior shelf between the metacone, but the paracone is broken and its protocone apex and the paracone base. In apex may not be properly attached. The pro- contrast to the derived condition exhibited tocone has a faint anterior basal cingulum by Micropternodus, there is no hypocone or and a weak posterior basal cingulum that fails posterolingual swelling ofthe protocone root. to reach as far as the metaconule. No hypo- M' is clearly Sarcodon-like, but has a less cone is present and the protoconal root is not well-developed hypocone, more widely sep- posterolingually swollen. arated paracone and metacone, and a slightly M3 has been suppressed. smaller metastylar wing. The metastylar wing At the posterior end of the lower jaw a has a steeply inclined, posterolingually-facing hooklike angular process occurs (fig. 3). The wear facet as in the type specimen of Sar- jaw is not inflected, however. The anterior codon pygmaeus, AMNH 20427. end of the lower jaw possesses an unfused M2 is a transverse, three-rooted tooth and symphysis, but the symphysis is not pro- has a reduced metacone. From the parastyle longed past Pl. Mental foramina occur be- the buccal border of the tooth is aligned pos- neath PI and P3, about halfway between the terolinguad. The paracone overtops the ventral and alveolar borders as in Sarcodon 1 984 MCKENNA, XUE, AND ZHOU: PROSARCODON LONANENSIS 7

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it l. - I&; ',il "I Z E r- E .t ,-. .h LO) >~~~~~~~~~~~~~.b i s'af -v :

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FIG. 4. Prosarcodon lonanensis McKenna, Xue, and Zhou, new genus and species. Northwest Uni- versity, Xian, PRC, specimen no. 78ShOO1, lower or middle Paleocene, Fangou Formation, Shimen Basin, Shaanxi Province, PRC. Occlusal views of upper right maxillary dentition (at left) and lower right and left dentitions (at right). Stereoscopic pair. See 5 mm. bar for scale.

pygmaeus (see Szalay and McKenna, 197 1). There are a total of five lower incisors pre- In general, the jaw is quite shallow, each ra- served, of which three are in the left jaw and mus being very little deeper than necessary two are in the right one (figs. 4, 6). Like the to accommodate the tips of the cheek-tooth upper incisors, we arbitrarily regard the lower roots (figs. 3, 5, 7). The coronoid process rises ones as permanent teeth. The second lower gradually behind the last molar, with a flat- incisor is the largest. I, is not spatulate, but tened anterior surface that borders a deeply 12 and I3 appear to be so (or to have been so excavated masseteric fossa. Lingually, the in early wear). coronoid process is also very slightly exca- The incisors are followed by a high, curved vated. In lateral aspect, the top of the coro- canine (presumably permanent), which lacks noid process is squared, the length ofthe pro- a posterior cutting crest but does possess a cess being maintained to the gently curved flattened lingual surface that meets the an- top, which abruptly terminates the dorsal end terior surface at an angle. The canine is single- of the process. This part of the coronoid is rooted. preserved on the piece of the specimen that Following a short diastema, a small, single- bears the upper dentition. rooted P1 (or dP,) juts forward. The tooth 8 AMERICAN MUSEUM NOVITATES NO. 2780

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s "I ` :1 U'o Ir W .. 4h ,. I I I%A -I .'t''-AL 4, -,-. I k p -ew II SI .- .0 O ., . .! C.. 't .. I w,,.- 1., 't. P. 4.. i i, f .1 - lu , o- FIG. 5. Prosarcodon lonanensis McKenna, Xue, and Zhou, new genus and species. Northwest Uni- versity, Xian, PRC, specimen no. 78ShOOl, lower or middle Paleocene, Fangou Formation, Shimen Basin, Shaanxi Province, PRC. Buccal view of left lower jaw and lingual view of right lower jaw. Stereoscopic pair. See 5 mm. bar for scale. bears a single cusp. It is followed by another basal cusp (paraconid) and a small heel cusp. short diastema. P4 is abruptly larger than P3 and is in fact P2 is double-rooted and leans forward. The a larger tooth than the lower molars, as in apex of its protoconid lies over its anterior Sarcodon pygmaeus. The trigonid ofP4 bears root. A tiny anterior basal cusp is present on a high protoconid, a low, centrally located the anterior base ofthe protoconid. From the and forward-projecting paraconid, and a low apex ofthe protoconid a concave crest curves metaconid that is closely appressed to the downward and then to the rear, where it ends lingual side of the protoconid and not so in a heel cuspule above the posterior root. widely separated from it as in M1. Both P4s Following another, very brief, diastema that are damaged, so that details of the heel are was presumably once the site ofan additional obscured by breakage, but the heel appears premolar in the remote ancestry of Prosar- to have consisted of a single, rather lingually codon (contra McKenna, 1975), P3 rises shifted crest, against which the paracone of erectly on its two roots, in contrast to the P4 would have lain in occlusion. The poste- "heeled-over" aspect of P1 and P2. The pro- rior cusp ofthe heel is shifted to the postero- toconid is located a bit anterior to the mid- lingual corner of the tooth. point of the tooth and bears an anterolingual M, is an elongate tooth with a well-devel- 1 984 MCKENNA, XUE, AND ZHOU: PROSARCODON LONANENSIS 9 oped heel. The trigonid bears the usual three cusps, of which the protoconid is easily the highest and most important. The paraconid is bladelike and projects linguad from the anterior base of the protoconid. The anterior base of the paraconid is very slightly indent- ed, presumably for the reception of the heel of dP4 during the eruption of M1. The inden- tation lies well above the heel of P4. The metaconid is widely separated from the-protoconid and is lower than the latter. The posterior surfaces of both cusps are flat and 5mm joined. A hypoconid, entoconid, and hypoconulid complete the tooth, enclosing an elongate talonid basin that is broadly open FIG. 6. Prosarcodon lonanensis McKenna, Xue, anterolingually. A low cristid obliqua crosses and Zhou, new genus and species. Northwest Uni- the heel to join the base ofthe trigonid about versity, Xian, PRC, specimen no. 78ShOO 1, lower midway across the tooth. Otherwise, the or middle Paleocene, Fangou Formation, Shimen morphology of the tooth is closely similar to Basin, Shaanxi Province, PRC. Anterior view of that of Sarcodon. lower incisors and canines. See 5 mm. bar for scale. M2 is an elongate tooth, principally because of the extreme length of its talonid. The trigonid is wide and larger, as well as more are maintained as in Ml, with the protoconid transverse, than its counterpart in M1. The being the largest and the paraconid the small- angle between the apices of the paraconid, est trigonid cusps. The elongate heel bears protoconid, and metaconid is more acute than the usual cusps, but the structure is narrow in M,. The size relationships of these cusps and the hypoconulid projects as a sharp cusp

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FIG. 7. Prosarcodon lonanensis McKenna, Xue, and Zhou, new genus and species. Northwest Uni- versity, Xian, PRC, specimen no. 78ShO01, lower or middle Paleocene, Fangou Formation, Shimen Basin, Shaanxi Province, PRC. Oblique view of lower jaws and traces of dorsal part of basicranium. See 5 mm. bar for scale. 10 AMERICAN MUSEUM NOVITATES NO. 2780

FIG. 8. Prosarcodon lonanensis McKenna, Xue, and Zhou, new genus and species. Northwest Uni- versity, Xian, PRC, specimen no. 78ShO01, lower or middle Paleocene, Fangou Formation, Shimen Basin, Shaanxi Province, PRC. Ventral view of basicranium. Stereoscopic view (at left) and interpretive drawing (at right). See 5 mm. bar for scale. Abbreviations: bo, basioccipital bone; dmw, descending medial wing (crista promentorii medio-ventralis) of petrosal bone; fc, fenestra cochleae; fo, foramen ovale; pgf, site of postglenoid foramen; pi, piriform fenestra; s, sphenoid bone.

far to the rear. The entoconid and hypoconid this is terminated by breakage at the anterior have a rearward tilt. At the anterior base of end ofthe top ofthe coronoid process, which the entoconid, a small secondary cuspule helps is still attached to the part of the specimen to delimit the lingual wall of the talonid ba- that bears the upper dentition. Between the sin. The cristid obliqua meets the rear of the two rami of the mandible and extending to trigonid wall about halfway across, as in M,. the rear is part ofthe basicranium ofthe skull. A faint anterior basal cingulum can be seen Breakage has left the ventral parts of the pe- on the front of M2, keyed to the talonid of trosal bones and a considerable extent of the M1. alisphenoid and basisphenoid bones (figs. 7, M3 has been suppressed. 8). Traces of the pterygoids are also present. When originally discovered, the maxillary BASICRANIUM: Breakage through the basi- teeth and the lower dentition ofthe type spec- cranium and ear region has resulted in the imen of Prosarcodon lonanensis were in oc- loss of most of the cranium in the type spec- clusion. The anterior end of a thin zygomatic imen of Prosarcodon lonanensis, but a few arch is preserved above the last molar, but features of the basicranium are preserved. In 1 984 MCKENNA, XUE, AND ZHOU: PROSARCODON LONANENSIS I11

separating the basisphenoid bone from the petrosal bone as in shrews, Nesophontes, Solenodon, Apternodus (contra Mc- Dowell, 1958), and various other lipotyphlans. The piriform fenestra is pro- portionally larger than that ofPalaeoryctes, about the same size as that ofApternodus. 4. The petrosal bone possesses a rudimen- tary descending medial wing (crista promentorii medio-ventralis of Kielan-Ja- worowska, 198 1), similar to that of leptictids and Diacodon and virtually identical with that of Palaeoryctes puercensis. 5. There is no bulla. The tympanic bone is presumably a free ring oriented nearly horizontally. 6. There is no trace of a groove crossing the ventral surface of the petrosal bone (to house either a promontory artery, a nerve, or both). 7. The fenestra rotunda (fenestra cochleae) is overlapped somewhat posteriorly by a flap of bone so that it appears to open directly ventrad (cochlear fossula of MacPhee, 1981, p. 51; recessus fenestra cochleae of Kielan-Jaworowska, 198 1). 8. A large postglenoid foramen for the ex- FIG. 8. Continued. ternal jugular vein can be seen in the left squamosal bone, far to the side and anterior to an anteroposterior groove in the roof of the external auditory meatus. the laboratory at the American Museum of 9. There is no pronounced sella turcica on Natural History, transparent epoxy resin was the dorsal surface of the sphenoid bone. applied to the dorsal surface ofthe remaining The area is flat, as in Lipotyphla generally. bone. Preparation ofthe ventral aspect of the MEASUREMENTS (table 1): Measurements glenoid and basicranial region was then ac- were taken from the right dentition unless complished with safety, revealing a ventral otherwise noted, with the same equipment morphology remarkably similar to that of and in the same manner as elucidated in Lil- Palaeoryctes (Matthew, 1913; McDowell, legraven, McKenna, and Krishtalka, 1981. 1958) and, in lesser degree, to that of the AP: upper and lower premolars-longest axis recently recognized early erinaceomorph ge- of crown, generally parallel to buccal side of nus Diacodon (Novacek et al., in press). Fea- tooth; upper molars-greatest measurement tures deemed to be important are as follows: at right angle to "width axis" dividing tooth into anterior and posterior halves; lower mo- 1. The glenoid fossa (anterior, articular sur- lars-greatest length ofcrown parallel to long face of entoglenoid process of McDowell, axis of tooth and exclusive of anterior cin- 1958) of the squamosal faces forward as gulum. ANW and POW: greatest anterior and in soricoids and palaeoryctoids. posterior widths, respectively, at right angle 2. A large foramen ovale is present. to AP measurements. LTRI: length of tri- 3. A piriform fenestra (McDowell, 1958, p. gonid, parallel to AP axis and exclusive of 128; MacPhee, 1981, p. 59) is present, anterior cingulum. 12 AMERICAN MUSEUM NOVITATES NO. 2780

TABLE 1 originally described from the same locality Measurements (in Millimeters) of and in the same paper as was Sarcodon, was Prosarcodon lonanensis shown to be a synonym ofthe latter by Szalay P1: AP 0.76, ANW 0.47 and McKenna (1971), who discussed what Diastema between PI and p2: 0.62 was then known of the animal, including the P2 AP 1.21, ANW 0.59 previously unrecognized lower jaw and den- P3: AP 2.36, ANW 1.34 tition and additional features of the upper P4: AP 2.56, ANW 2.63 (breakage corrected), POW dentition. On the basis ofthe type and newly 2.48 (breakage corrected) referred material, Szalay and McKenna con- MI: AP 2.40, ANW 3.26 (approximate), POW 3.85 cluded that Sarcodon was a member of the M2: AP 1.49, ANW 3.89, POW 2.11 Deltatheridiidae, which in 1971 they regard- P'-M2 length: 10.91 ed as a family of palaeoryctoid insectivores. PI: AP 0.96 However, they denied special relationship of P2: AP 1.25 Sarcodon to Micropternodus, holding that P3: AP 1.55 (approximate) P4: AP 2.57 (approximate), LTRI 1.46, ANW 1.18, there was no special similarity of the newly POW 1.18 (approximate) recognized lower dentition of Sarcodon (i.e., MI: AP 2.18, LTRI 1.24, ANW 1.70, POW 1.27 that of its synonym Opisthopsalis) to that of M2: AP 2.74, LTRI 1.22, ANW (left) 1.74, POW 1.19 Micropternodus. Szalay and McKenna (1971) I-M2 length in lower jaw: 15.47 therefore believed mutual similarities of the Approximate skull length (originally): 30.0 upper dentitions of Sarcodon and Microp- Approximate skull width (originally, at orbit, zygoma ternodus to be the results of convergence. to zygoma): 21.0 With the collection of Sinosinopa sinensis from the early to middle Eocene Arshanto Formation southwest ofErlian [Erhlien, etc.], Nei Mongol, a second, more primitive, Asian DISCUSSION: Prosarcodon is a small, prim- line of Sarcodon-like insectivores was made itive relative of Sarcodon. As in Sarcodon, known (at least by name) by Qi (1979). Casts Prosarcodon has lost both an upper and a ofthe dentition ofthis specimen are available lower molar, presumed to be M3 and M3. to the authors. Sinosinopa differs from Sar- For a long time after its initial description codon and Prosarcodon in that it retains all by Matthew and Granger (1925), Sarcodon three molars. In Sinosinopa both M' and M2 was an enigma. The genus is now known from possess a hypocone thatjuts strongly postero- the latest Paleocene or earliest Eocene (Clark- linguad; in Prosarcodon M2, the last molar, forkian equivalent) Gashato and Naran Bu- possesses a narrow cingulum-like hypocone. lak sediments of the MPR (Dashzeveg and P4 of Sinosinopa is more elongate than in McKenna, 1977) and from the earliest Eocene either Sarcodon or Prosarcodon. or latest Paleocene Nomogen fauna of Nei AFFINITIES: Prosarcodon, Sarcodon, and Mongol (Inner Mongolia), PRC (Zhou, Qi, Sinosinopa seem to be palaeoryctoid insec- and Li, 1976; Chow (Zhou) and Qi, 1978; Qi, tivores, but palaeoryctoids are no longer be- 1979). On the basis of the type specimen of lieved to be especially related to the Asian Sarcodon pygmaeus, Van Valen (1966) be- and possibly American Cretaceous family lieved Sarcodon to be closely related to the Deltatheridiidae (Butler and Kielan-Jawo- palaeoryctid genus Pararyctes, but stated that rowska, 1973; Fox, 1974, 1975, 1976). Rath- Sarcodon is intermediate between palaeoryc- er, Palaeorcytes and its closest palaeoryctoid tids and Micropternodus. In his classification allies appear to be related to lipotyphlan in- published the next year, Van Valen (1967) sectivores (Lillegraven, McKenna, and placed Sarcodon in the Micropternodontidae Krishtalka, 1981) as well as to the Ferae. That and placed the Micropternodontidae in the Prosarcodon, Sarcodon, and Sinosinopa are Superfamily Palaeoryctoidea, in turn in the lipotyphlan insectivores is suggested by the Hyaenodonta, a suborder of Van Valen's or- presence of a piriform fenestra in Prosarco- der Deltatheridia. Several years later, Opis- don. None of these Asiatic genera is zalamb- thopsalis vetus Matthew and Granger, 1925, dodont, as Palaeoryctes and Pararyctes had 1984 MCKENNA, XUE, AND ZHOU: PROSARCODON LONANENSIS 13 nearly become, but a trend toward zalamb- The taxonomic history of Micropternodus dodonty was under way. Prosarcodon and is, like that of many other fossil insectivo- Sarcodon became specialized in the loss of a rans, checkered. In 1903 Matthew described molar, but the latest-occurring member ofthe two new genera and species of insectivorans, group in Asia, Sinosinopa, is less specialized Apternodus mediaevus and Micropternodus in that particular regard, although it is more borealis, from Chadronian (approximately specialized in having jutting hypocones on lower Oligocene) deposits at Pipestone several upper molars. Springs, Montana. Matthew regarded both Among palaeoryctoids and palaeoryctoid- genera to be descriptively as well as taxo- like derivitives similar to Sinosinopa, Pro- nomically zalambdodont insectivores, al- sarcodon, and Sarcodon, the American genus though at that time only the lower jaws of Micropternodus Matthew, 1903 (=Kentro- each were known and therefore the nature of gomphios White, 1954) immediately comes the upper dentitions could only be estimated. to mind, as it did to Van Valen (1966, 1967) Matthew also stated (1903, p. 199) that Mi- before us. Micropternodus is an Eocene (Rob- cropternodus might be allied to Centetodon inson, Black, and Dawson, 1964; Novacek, pulcher Marsh, 1872, now recognized to be 1976), Oligocene (Matthew, 1903, 1909; a geolabidid insectivoran but which was then White, 1954; Russell, 1960), and Oligo-Mio- known only from the Bridgerian (See Lille- cene (Stirton and Rensberger, 1964) Ameri- graven, McKenna, and Krishtalka, 1981, for can insectivore, in which Sarcodon-like hy- a review of the taxonomic history of Cen- pocones are present on P4-M2, but in which tetodon). In a semipopular paper, Matthew P' was lost by the Oligocene and P2 by the (1905, p. 49) placed both Centetodon and Oligo-Miocene. Ii was enlarged in Microp- Micropternodus in the Centetidae (Tenreci- ternodus (CM 8674), as was the upper canine dae). Two years later, Leche (1907, p. 54) tooth, which ultimately came to have a tri- regarded both Micropternodus and Apterno- angular cross-section. The snout of Microp- dus as leptictids differing in talonid structure ternodus is highly specialized (Russell, 1960) from centetids (tenrecids). Matthew (1909a) and the infraorbital foramen of Micropter- next placed Micropternodus in "Fam. indet." nodus is far to the rear (White, 1954, fig. 43) among the Insectivora, but in his monograph rather than over P3 as it still was in Sinosi- on Bridgerian (approximately middle Eocene) nopa or over the anterior root of P4 as it was mammals Matthew (1909b, p. 543) consid- in several undescribed American early Eocene ered Micropternodus as effectively a genus palaeoryctid skulls (UM 68074, 72624) cur- incertae sedis among the Zalambdodonta. rently under study by McKenna. In another Excellent photographs of the type specimen palaeoryctid skull (UM 80855) from the Pa- of Micropternodus borealis appear on plate leocene ofMontana, the infraorbital foramen 51 of Matthew's monograph. Moreover, is above the rear ofP4. As is suggested by the Matthew (1909b, p. 543; 1928, p. 975) was cheek-teeth, if Sinosinopa lies close to the ofthe opinion that Marsh's Centetodon is not ancestry ofMicropternodus then much ofthe a zalambdodont. This was eventually con- specialization of the snout and reduction of firmed when the upper dentition of Cen- the zygomatic arch and its base near the in- tetodon was recognized (Lillegraven, Mc- fraorbital canal would have taken place dur- Kenna, and Krishtalka, 1981). ing the middle and late Eocene prior to the Matthew's early insight about the descrip- known appearance of specialized skull mor- tive zalambdodonty of the upper molars of phology in Micropternodus, as exemplified by Apternodus was soon proven correct (Mat- specimens from the early Oligocene of Mon- thew, 1910). However, when the upper mo- tana (White, 1954; Russell, 1960). These aut- lars ofMicropternodus finally became known apomorphies separate Micropternodus from a half-century after the animal's debut, they other genera by considerable morphologic were found to possess well-developed meta- distance, but they do not alter cladistic re- cones in addition to paracones (White, 1954; lationships based upon postulated shared-de- Russell, 1960), although the bases of the rived cheek-tooth patterns. paracone and metacone are fusing on each 14 AMERICAN MUSEUM NOVITATES NO. 2780 molar and suggest the beginning stages of za- 2. The anterior part ofthe orbit is somewhat lambdodonty as in Palaeoryctes and Para- crushed. ryctes. 3. There was probably a small lacrimal fo- Broom (1909, p. 133) remarked that the ramen. (lower) molars of both Apternodus and Mi- 4. Foramina for the palatine nerve and ar- cropternodus are essentially similar to those tery penetrate the postpalatine torus in the of Cenozoic chrysochlorids and Jurassic usual places. Phascolestes and Amphitherium, but, with his 5. Although most of the sutures of the ros- usual perspicacity, he also noted a similarity trum are fused, those separating the pal- to Eocene Palaeosinopa and Palaeonyctis. atine bones from the maxillaries on the Gregory (1910, pp. 558, 559) regarded Mi- rear of the palate are faintly visible. The cropternodus as an American fossil chrysoch- palatines extended forward to the level of lorid but also suggested that it might be a the hypocone of M'. primitive centetid (tenrecid). Schlosser (19 1 1, 6. M3 has a mesostyle. p. 166) placed Micropternodus as an intermediate between centetids (tenrecids) and McDowell (1958) rescued Micropternodus Potamogale on the one hand, and the leptic- borealis from the Solenodontidae but rein- tids on the other. Osborn ( 1910, p. 520), Mat- carcerated it as a nyctitheriid without, how- thew(1913, p. 308; 1919, p. 174), Hay (1930, ever, recognizing that its cell mate, "Kentro- p. 427), Schlaikjer (1933, p. 20), and Scott gomphios," is synonymous with it at the and Jepsen (1936, p. 12) all believed that generic level. Robinson, Black, and Dawson Micropternodus is allied with the Solen- (1964), without comment, also placed Mi- odontidae of the West Indies. In each case cropternodus in the Nyctitheriidae. the conclusions ofall these authors about Mi- Russell (1960), following a personal com- cropternodus were based solely on the lower munication to McKenna from John Clark of jaw and its dentition. The upper denitition the Carnegie Museum, recognized that was not to be made known until 1954. White's "Kentrogomphios" strophensis is White (1954) described the first known ros- congeneric with Matthew's Micropternodus trum of Micropternodus (as that of a sup- borealis, described a half-century earlier. posedly new genus, Kentrogomphios) and fig- Russell reviewed the history of study of Mi- ured for the first time the upper dentition of cropternodus and concluded that the genus is Micropternodus strophensis. Without stating an insectivoran (lipotyphlan), but that it can- his reasoning, White placed "Kentrogom- not be placed in the Talpidae, Solenodonti- phios" strophensis in the Nyctitheriidae. Pre- dae, Apternodontidae, or Nyctitheriidae. sumably, relegation to this family of insec- Presumably, he did not consider it necessary tivorans resulted from White's conclusions to mention other, less closely related families. that the animal was not a soricid and not Russell left Micropternodus as a genus incer- definitely a talpid. Thus, the Nyctitheriidae tae sedis within the Insectivora, the latter as then understood represented a stem "sor- being considered identical with Lipotyphla in icoid" scrap basket into which White's "new content. genus" could be tossed. Stirton and Rensberger (1964) described Examination of USNM 18870, type of Micropternodus morgani, an advanced "Kentrogomphios" strophensis White, 1954, species from the Oligo-Miocene John Day has revealed several features not adequately beds ofOregon. They placed Micropternodus illustrated by White (1954, fig. 43). We take in a monotypic family within the Erinaceo- the opportunity to correct or comment on idea. them here: Recently, Ostrander (1983, p. 129) has commented upon Micropternodus and has named a new species, Micropternodus mon- 1. The roots of the molars are not visible trosensis, from the Chadronian (approxi- because they are remarkably closely held mately lower Oligocene) of Nebraska. How- in the maxilla, as in several other kinds ever, the new species appears to belong to a of lipotyphlans. true genus of Erinaceoidea and is not an ally 1984 MCKENNA, XUE, AND ZHOU: PROSARCODON LONANENSIS 15 ofMicropternodus. Among other reasons, the theory. Annals Natal Govt. Mus., vol. lower teeth of"M." montrosensis are too low- 2, no. 1, pp. 129-139, pl. 2. crowned to belong to Micropternodus. Os- Butler, P. M., and Z. Kielan-Jaworowska trander's conclusion that his new species may 1973. Is Deltatheridium a marsupial? Nature, have erinaceoids is vol. 245, no. 5420, pp. 105-106, 1 fig. descended from Eocene Chow (Zhou), Min-chen (Mingzhen), and Qi Tao logical, but this has no bearing on the taxo- 1978. Paleocene mammalian fossils from nomic fate of Micropternodus if "M." mon- Nomogen Formation of Inner Mongo- trosensis is unrelated to it. lia. Vertebrata PalAsiatica, vol. 16, no. Since 1956 Cryptoryctes Reed (1954) has 2, pp. 77-85, 2 figs., 4 pls. come to be regarded with increasing convic- Clark, J. tion as a second synonym ofMicropternodus. 1937. The stratigraphy and paleontology ofthe Cryptorcytes kayi was based upon a humerus Chadron Formation in the Badlands of somewhat like that of proscalopine talpids, South Dakota. Ann. Carnegie Mus., vol. not upon a dentition. To date, no Crypto- 25, no. 21, pp. 261-350, figs. 1-12, pls. 21-26. ryctes humerus has ever been found in an Dashzeveg, D., and M. C. McKenna articulated specimen that includes a denti- 1977. Tarsioid primate from the early Ter- tion; thus its reference to Micropternodus is tiary ofthe Mongolian People's Repub- based on provenience, size, frequency of oc- lic. Acta Palaeont. Polonica, vol. 22, no. currence, and subjective estimate. But ifReed 2, pp. 119-137, figs. 1,2, pls. l,2, tables (1956), Russell (1960), and Reed and Turn- 1, 2. bull (1965) have correctly inferred that the Fox, R. C. material upon which Cryptoryctes is based 1974. Deltatheroides-like mammals from the actually represents the humerus of Microp- Upper Cretaceous of North America. ternodus, then by the Oligocene Micropter- Nature, vol. 249, no. 5455, p. 392, 1 fig. 1975. Molar structure and function in the Ear- nodus had departed from the primitive con- ly Cretaceous mammal Pappotherium: dition and had acquired a peculiarly modified evolutionary implications for Mesozoic humerus, adapted to talpid-like rather than Theria. Canadian Journal of Earth Sci- terrier-like digging. Van Valen (1966) de- ences, vol. 12, no. 3, pp. 412-442, 18 scribed a fragmentary humerus of Palaeo- figs. ryctespunctatus, implying that it is somewhat 1976. Additions to the mammalian local fau- talpid-like but nevertheless adapted to ter- na from the Upper Milk River For- rier-like digging. A palaeoryctoid relation- mation (Upper Cretaceous), Alberta. ship of micropternodontines is thus not pre- Ibid., vol. 13, no. 8, pp. 1105-1118, 7 cluded by the morphology of the humerus. figs. Gregory, W. K. A remote linkage with the soricoid genus 1910. The orders of mammals. Bull. Amer. Centetodon (Matthew, 1903; Novacek, 1976; Mus. Nat. Hist., vol. 27, pp. 1-524, 32 Lillegraven, McKenna, and Krishtalka, 198 1) figs. is also indicated, but in that subfamily of Hay, 0. P. soricoid insectivores P, remained double- 1930. Second bibliography and catalogue of rooted, whereas in Prosarcodon P, was al- the fossil vertebrata of North America. ready single-rooted and in Micropternodus Vol. II. Washington, Carnegie Institu- presumably was lost. Russell (1960) suggest- tion of Washington, 1074 pp. ed (echoing Matthew, 1903, p. 199) that Mi- Kielan-Jaworowska, Z. cropternodus and Oligocene species of Cen- 1981. Evolution of the therian mammals in the Late Cretaceous of Asia. 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