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Postcranialanatomy and habits of Asian multituberculate mammals ZofiaKielan- Jaworowska andPetr P. Gambaryan
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An international journal of palaeontology and stratigraphy An international journal of Quaternary research Scandinavian University Press, P.O. Box 2959, Tøyen, N-0608 Oslo 6, Norway Postcranial anatomy and habits of Asian multituberculate mammals
ZOFIA KIELAN-JAWO ROWSKA AND PETR P. GAMBARYAN
Kielan-Jaworowska, Z. & Gambaryan, P.P. 1994 12 15: Postcranial anatomy and habits of Asian multituberculate mammais. Fossils and Strata, No. 36, pp. 1-92. Oslo. ISSN 0300-9491. ISBN 82- 00-37650-8.
Postcranial skeietal elements of six Late Cretaceous taeniolabidoid taxa from the GobiDesert are described, and the postcranial musculature of Kryptobaatar and Nemegtbaatar is reconstructed. A new reconstruction of multituberculate pes is given, showing Mt lI! abducted 30° from the longitudinal axis of the tuber calcanei. The calcaneo--MtV contact and abduction-adduction at the astragalonavicular joint in a horizontal plane, around a vertical axis, are recognized as new multituberculate autapomorphies. Other new, partly plesiomorphic, multituberculate characters are: no transverse foramen in atlas; cervical ribs present at least in some taxa; large iliosacral angle (35-37°); iliosacral contact dorsoventral rather than mediolateral; an incipient supraspinous fo ssa and a peg-like acromion. The deep multituberculate pelvis with femoral adductors originating ventraI to the acetabulum and the large mediolateral diameter of the tibia indicate abduction of the fe mora by 30-60°, while twisting of the humerus is indicative of abducted fo relimbs. Long spinous processes of the lumbar vertebrae, sloping craniodorsally in Asian multituberculates, suggest asymmetrical gait and long jumps, but the short tibia and short Mt lI! suggest short jumps. This inconsistency is due to the abducted limbs, because of which the direct transposition of jump mechanics of mammals with parasagittal limbs does not work for multituberculates. Multituber culates possibly had a steeper trajectory ofjump than modem therian mammals. The studied Asian multituberculates do not show adaptations to arborealism. It is suggested that the coracostemal joint disappeared in multituberculates (and independently in therians) as an adaptation to asymmetrical gai!. It is speculated that the competitive inferiority of multituberculates to eutheri ans is related to the structure of the pelvis with a ventraI keel, which hindered prolongation of the gestation period, and to abducted limbs that limited their endurance for prolonged running. The analysis of multiturbeculate-therian postcranial synapomorphies does not support the idea that Multituberculata is the sister taxon of Theria. DMammalia, Multituberculata, Anatomy, Creta ceous, Asia.
Zofia Kielan-Jaworowska, Paleontologisk Museum, Universitetet i Oslo, Sars Gate 1, N--0562Oslo 5, Norway; Petr P. Gambaryan, Zoological Institute, Russian Academy of Sciences, Universitetskaya Naberezhnaya 1, 199164 St. Petersburg, Russia; 27th September, 1993; revised 21st April, 1994.
Contents
Introduction ...... 3 Genus Nemegtbaatar Kielan-Jaworowska, 1974 ...... 17 Terminology ...... 5 Nemegtbaatar gobiensis Kielan-Jaworowska, 1974 ...... 17 Osteological descriptions ...... 6 Skull ...... 17
Suborder Cimolodonta McKenna, 1975 (new rank); Infraorder Axial skeleton ...... 17
Taeniolabidoidea Sloan & Van Valen, 1965 (new rank); Pectoral girdle and forelimb ...... 22 Family Eucosmodontidae Jepsen, 1940 ...... 6 Pelvis and hind limb ...... 26 Genus KryptobaatarKielan- Jaworowska, 1970 ...... 6 Genus Chulsanbaatar Kielan-Jaworowska, 1974 ...... 30 Kryptobaatardashzevegi Kielan-Jaworowska, 1970 ...... 6 Chulsanbaatar vulgaris Kielan-J aworowska, 1974 ...... 30
Skull ...... 6 Skull ...... 31
Axial skeleton ...... 6 Hyoid apparatus ...... 31
Pectoral girdle (forelimb unknown) ...... 7 Axial skeleton ...... 32 Pelvic girdle and hind limb ...... 7 Pectoral girdle and forelimb ...... 36 Pelvic girdle and hind Iimb ...... 36 Anatomical comparisons ...... 57 Family Sloanbaataridae Kielan-Jaworowska, 1974 ...... 38 Proportions of the body ...... 57 Genus Sloanbaatar Kielan-Jaworowska, 1970 ...... 38 Hyoid apparatus ...... 57 Sloanbaatar mirabilis Kielan-Jaworowska, 1970 ...... 38 Vertebral column ...... 57 Axial skeleton ...... 38 Pectoral girdle and fo relimb ...... 60 Pelvie girdle and hind limb ...... 38 Pelvie girdle and hind limb ...... 62 Family Taeniolabididae Granger & Simpson, 1929 ...... 39 Functional anatomy ...... 65 Genus Catopsbaatar Kielan-Jaworowska, 1994 ...... 39 Reconstruction oflocomotion ...... 65 Catopsbaatar catopsaloides (Kielan-Jaworowska, 1974) ...... 39 Structure and function of multituberculate pes ...... 74 Taeniolabidoid, fa m. gen. et sp. indet. (Kielan-Jaworowska 1989) ... 40 Pedal adaptations of Asian and North American Axial skeleton ...... 40 multituberculates ...... 79 Pectorai girdle ...... 40 Forelimb movements ...... 82 Myological reconstructions ...... 40 Concluding remarks ...... 82
Muscles of the fo relimb ...... 40 Plesiomorphies and apomorphies of multituberculates ...... 83 Muscles of the axial skeleton ...... 45 Habits and extinction ...... 85
Muscles of the pelvie girdle and hind limb ...... 47 References ...... 88 Introduction
Remains of the Multituberculata (assigned to a subclass of equivalents) in the Gobi Desert, assembled by the Polish their OWl1,Allotheria Marsh, 1880) are found in deposits that Mongolian Palaeontological Expeditions, and to reconstruct range in age from the Late Triassic (Rhaetian; Sigogneau musculature and habits ofthe animals. The exact age ofthese Russell l989) through Late Eocene (recognized previously as fo rmations remains an open question (e.g., Gradzmski et al. Early Oligocene by Krishtalka et al. 1982, but see Swisher & 1977; Fox 1978; Lillegraven & McKenna 1986). We tenta Prothero 1990). Although multituberculates are the most tively follow the estimates given by Gradzmski et al. (1977): common fo ssils in the majority of well sampled Late Creta the Djadokhta Formation (and its stratigraphic equivalent ceous and Paleocene localities in the Northern Hemisphere, the Toogreeg beds) is regarded as upper Santonian and/or their postcranial remains are rarely found and are still in lower Campanian; the Barun Goyot Formation (and its completely knOWl1. stratigraphic equivalent the Red beds ofKhermeenTsav) as Multituberculate postcranial elements or partial skeletons middle Campanian. have been found only in members of the Cimolodonta The most complete postcranial skeletons described here
McKenna, 1975 (a taxon erected as an infraorderto include belong to Kryptobaatar dashzevegi Kielan - J aworowska, 1970, the 'parvorders' Ptilodontoidea Sloan & Van Valen, 1965, Nemegtbaatar gobiensis Kielan-Jaworowska, 1974, and Chul and Taeniolabidoidea Sloan & Van Valen, 1965, the latter sanbaatar vulgaris Kielan-Jaworowska, 1974; less complete two regarded by us as infraorders). The cimolodont postcra postcranial fragments of Sloanbaatar mirabilis Kielan nial fragmentsfrom the Paleocene or, less often,Late Creta Jaworowska, 1970, Catopsbaatarcatopsaloides (Kielan-Jawo ceous, were described or diseussed in the 20th century by rowska, 1974) and a taeniolabidoid, fam., gen. et sp. indet. Gidley (1909), Broom (1914), Simpson (1926, 1928a, 1937), (Kielan-Jaworowska 1989), are also brietly described (see Simpson & Elftman (1928), Granger & Simpson (1929), Kielan-Jaworowska 1970, 1971, 1974, 1994; Kielan-Jawo McKenna (1961), Clemens (1963), Deischl (1964), Sloan & rowska & Sloan 1979; Kielan-Jaworowska et al. 1986; and Van Valen (1965), Kielan-Jaworowska (1969, 1979, 1989), Hurum 1992, 1994, for description of the skulls of these Sahni (1972), Jenkins (1973), Kielan-Jaworowska & Dashze taxa). All Asian Late Cretaceous multituberculates belong to veg (1978), Jenkins & Weijs (1979), Krause & Baird (1979), the Taeniolabidoidea. We describe the postcranial skeletons Krause & Jenkins (1983), Jenkins & Krause (1983), Kielan of the above-mentioned taxa, beginning with those that are Jaworowska & Qi (1990), Sereno & McKenna (1990), more complete or better preserved. As the taeniolabidoid Kielan -J aworowska & Nessov (1992) and Szalay (1993). The postcranial skeleton is fairly uniform morphologically, the most comprehensive work to date is the paper by Krause & description of elements that do not differfrom those better Jenkins (1983), which includes the description of a fairly preserved in other taxa is omitted. complete postcranial skeleton of the Paleocene genus Ptilo In contrast to the North American Late Cretaceous, where dus, as well as a thorough review ofmultituberculate postcra the postcranial mammalian skeletons are preserved as iso nial literature, including 19th century papers of Cope and lated elements (e.g., Clemens 1963; McKenna 1961; Deischl Marsh, not cited by us. 1964; Sloan & Van Valen 1965; Szalay & Decker 1974; Sahni The aim ofthis monograph is to describe multituberculate 1972; Szalay 1984, 1993; Krause & Baird 1979; Krause & postcranial material from the Late Cretaceous Djadokhta Jenkins 1983; Bleefeld 1992; see also Clemens & Kielan and Barun Goyot formations (and their stratigraphic Jaworowska 1979 for review), the Late Cretaceous Gobi 4 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
Desert postcranials occur as more or less complete articu share ecological specializations with the multituberculates lated skeletons. This has its obvious advantages, but also presented here. some drawbacks. Because of the scarcity of the material (e.g., The muscle scars (especiaUy of small muscles) preserved the postcranial skeleton of Kryptobaataris known froma on the bones of the studied multituberculates are not always single specimen) and the minute size of most of the taxa, it obvious. As multituberculates differ from extant marsupial proved impossible to separate the particular bones and ex and eutherian mammals in many important details of their amine them fromall sides. Consequently, the articular sur cranial and postcranial anatomy, it is possible that some faces in most cases could not be studied. For comparative muscles present in extant mammals used by us fo r compari purposes we studied isolated postcranial elements of the Late sons were not present in multituberculates and vice versa. Cretaceous North American multituberculates, a partial For these reasons, our reconstructions of multituberculate skeleton of ?Eucosmodon sp. from the Paleocene of North musculature should be considered as best approximations. America and humeri of ?Lambdopsalis bulla Chow & Qi, In order to understand the position and movements of 1978, fromthe Eocene of China, in which articular surfaces, multituberculate hind limbs, a plastic model of an idealized and sometimes also muscle scars, are weU preserved. pelvis and hind limbs (based on Kryptobaatar and Nemegt Reconstructions of the musculature of fo ssil mammals baatar) has been made. Because of the incompleteness of the have rarely been attempted, although there is a wealth of material, it was impossible to make such a model of the skeletal remains. The difficulties and reliability of muscle fo relimbs and shoulder girdle. Our reconstructions ofmulti reconstructions in fo ssil vertebrates were recently summa tuberculate hind-limb movements during the propulsive rized by Bryant & Seymour (1990) and Bleefeld (1992). In phase (Figs. 51-53) are partly based on this model. spite of these difficulties,we believe that in cases when bone Origins of multituberculates and their relationships to surface is exceUently preserved, relatively reliable muscle other mammals are debated (see, e.g., Crompton & Jenkins reconstructions in fo ssil mammals are possible. 1973; Hahn 1973; Jenkins 1984; Hopson & Barghusen 1986; The masticatory apparatus and jaw movements of multi Kemp 1982, 1983; Rowe 1988, 1993; Szalay 1990, 1993; tuberculates were reconstructed by Simpson (1926) for the Wible 1991; Kielan-Jaworowska 1992; Miao 1991, 1993; and Late Jurassic Ctenacodon, by Sloan (1979) for the Paleocene Wible & Hopson 1993 for recent reviews). The problem of Ectypodus, and by Krause (1982) and WaU & Krause (1992) the origins and relationships of multituberculates is beyond for the Paleocene Ptilodus (see also Broom 1910; Simpson the scope of the present monograph. However, we hope that 1933; Turnbull 1970; Gingerich 1977, 1984; Hopson et al. the recognition of multituberculate plesiomorphies and 1989, for discussion of multituberculate jaw mechanics). As apomorphies based on the postcranial anatomy may bring far as the postcranial skeleton is concerned, Simpson & new data for understanding the relationships of multituber Elftman(19 28) reconstructed the hind-limb musculature of culates to other mammals. ?Eucosmodon from the Paleocene of North America, while Acknowledgments. - During the work on this monograph we greatly bene Jenkins & Krause (1983) and Krause & Jenkins (1983) dis fittedfrom discussion and correspondence with numerous colleagues. We cussed climbing specializations of Ptilodus and ?Eucosmo are especially grateful to David W. Krause, Kenneth D. Rose and Fred S. don. The musculature of Cretaceous multituberculates has Szalay who read the whole manuscript and offered most useful criticism not been reconstructed as yet. and suggestions. We appreciate also the assistance of other colleagues who read parts of the manuscript and commented on it. Prime among them We reconstruct the postcranial musculature ofKr yptobaa were: Ann R. BleefeId, Percy M. Butler, jean-Pierre Gasc, Farish A. jenkins, tar and Nemegtbaatar and some muscles of Chulsanbaatar, jr., Francoise K. jouffroy, Alexander N. Kuznetsov, Denise Sigogneau Sloanbaatar, an unidentified taeniolabidoid from the Dja Russel! and Hans-Dieter Sues. Malcolm C. McKenna (American Museum dokhta Formation, and Lambdopsalis. Although the neck ofNatural History, New York) and Qi Tao (Institute ofVertebrate Paleon tology and Paleoanthropology, Beijing) kindly al!owed us to study the vertebrae in Nemegtbaatar and Chulsanbaatar have been speeimens in their charge. The specimens described by us were prepared preserved, it was impossible to reconstruct the neck muscles during severaI years by the members of the technical staffof the Institute of because the relevant muscle scars were not discernible. Paleobiology of the Polish Academy ofSciences in Warsaw. Anna Ohand We have studied in detail and figured the skeletons and ganian-Gambaryan (St. Petersburg) generously offeredher time for vari ous kinds of technical assistance. The photographs were taken partly at the musculature of several extant, small, terrestrial marsupials Institute of Paleobiology in Warsaw by the late Maria Czarnocka and by and rodents: the marsupial Antechinus stuarti and the ro Elzbieta Mulawa and Marian Dziewinski, the remainder at the Palaeonto dents Meriones blackleri, Meriones tamariscinus and Mesocri logical Museum, Oslo by Per ÅS. The drawings have been inked by Evgenii cetus branti. In addition, many other extant species that are A. Bessonov, Natalia A. Florenskaya and Galina E. Zubtsova in St. Peters burg. Jørn Hurum (Palaeontological Museum, Oslo) helped us in com not figured have been dissected, measured and studied puter editing of the drawings. The work of ZKj has been supported by (Tables 1-6). Comparisons with the musculature of mono Norges Allmenvitenskapelige Forskningsråd, grants Nos. 441.91/002, trerneswas less useful,because of their locomotor specializa 441.92/003 and 441 .93/001. The work ofPPG has been supported by the tions. All extant monotrernes (Ornithorhynchus, Tachyglos Russian Academy of Sciences, grant no. 93-04-07699. PPG received from the Polish Academy ofSciences a fe llowship to visit Warsaw in 1979, when sus and Zaglossus) are powerful diggers, and in addition our cooperation started. The cooperation was subsequently postponed for Ornithorhynchusis adapted to a semi-aquatic mode oflife. In severaI years and then renewed in 1991 when PPG received a grant from contrast, smallmarsupial and eutherian mammals appear to Norges Allmenvitenskapelige Forskningsråd to visit Oslo and then a fel- FOSSILS AND STRATA 36 (1994) Anatomy and habits of multitubereulates 5 lowship for stay in Oslo from December 1992 to March 1993. The visits of 1957 edition) did not give fo rmal names to the two phases, ZKJ in St. Petersburg in May 1993 and ofPPG in Oslo in September 1993 but he spoke about the 'flight'with outstretched legs and the were supported in part by the University of Oslo. The publication of this monograph is funded by Norges Allmenvitenskapelige Forskningsråd, 'spring' with legs flexed under the body. The two phases grant No. 441.93/004. To all these persons and institutions we would like to together have been referred to as 'unsupported period' (Hil express our sincere thanks and gratitude. debrand 1960) or 'free flight' (Gambaryan 1974). Howell (1944) called the phase with extended legs the 'centrifugal suspension' and the one with gathered legs 'centripetal sus Terminology pension' . The same phases have been referred to respectively as 'extended' and 'bunched suspension' (Brown & Yalden Until recently, Monotremata were assigned to the subclass 1973), 'extended' and 'gathered suspension' (Hildebrand Prototheria Gill, 1872, and Theria Parker & Haswell (1897) 1988), and 'extended' and 'crossed flight' (Gambaryan included Marsupialia, Eutheria and extinct groups tradition 1974). 'Free flight' of Gambaryan (1974) is a translation of ally classifiedas Symmetrodonta and Eupantotheria (but see the term '
Jouffroy(19 71). tor, c. == caput, C == cervical vertebrae, Cd == caudal vertebrae,
The terminology of the gait is confusing. We follow Jen cond. = condylus; D I - D V == digits I-V, ext. == extensor, f. = kins & Goslow (1983) using propulsive phase (rather than fo ramen, fac. = facies, fl.= flexor, inc. = incisura, L = lumbar
'phase of support' of Howell 1944 and Gambaryan 1974) vertebrae, lig. = ligamentum, m. = muscle, Mt I - Mt V == when the fo ot (or feet) strikes the ground. In galloping metatarsals I-V, p. == pars, Ph 1-3 == phalanges 1-3, proc. == mammals there may occur two phases when all fo ur feet are processus, S = sacral vertebrae, T = thoracic vertebrae, troch. clear of the ground. Muybridge (1877, cited here from the = trochanter. 6 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
(preserved on both sides) are relatively long and stout, indi Osteological descriptions cating the presence of stout laminae. C3-C5 are badly dam aged; only fragments of the bodies with bases of the left Suborder Cimolodonta McKenna, 1975 transverse processes are preserved. (new rank) Lumbar vertebrae (Figs. 2, 3A, B, 6C, see also Fig. 4 fo r method of measurements of the vertebrae). - The prezyga Infraorder Taeniolabidoidea Sloan & Van pophyses (cranial articular surface, zygapophysis cranialis, Valen, 1965 (new rank) proc. articularis cranialis) and postzygapophyses are very large. The lateral walls of the pedicles are strongly concave. Family Eucosmodontidae Jepsen, 1940 The spinous processes (broken), preserved on L6 and L7, arise from thewhole length of the arch and are massive, on L7 Genus Kryptobaatar Kielan -Jaworowska, directed upwards, only slightly directed cranially, on L6 1970 more strongly inclined cranially. The preserved parts of the spinous processes show that they were very long, much Synonym. - Gobibaatar Kielan-Jaworowska, 1970 longer than in Meriones (see Fig. 36A). The transverse pro cesses are broken off; judgingfrom the preserved parts they Kielan were wider and more massive on L6 than on L7. There is a Kryptobaatar dashzevegi median ventral crest (crista ventralis) on L5 and L6. Jaworowska, 1970 Sacrum (Figs. 2, 3A-C). - The preserved parts of the sacrum (Figs. 1-3, 5-7, 37D, 44A, 54, 59A) consist of S 1-S2, a fragment of S3, and, some distance Material. - Djadokhta Formation, Bayn Dzak, about l km caudally, a tiny fragmentof S4 in articulation with Cdl. As eastward fromthe Main Field, ZPAL MgM-I/4l (the speci the sacrum is firmlyfused to the pelvis, its surface for articu men was fo und in situ): damaged skull and partial right lation with the latter cannot be examined. dentary, badly damaged axis and leftside of C3-C5, incom The estimated length of the sacrum is about 16 mm, its plete right scapulocoracoid, and in anatomical succession maximal width across the auricular surfaces is about 7 mm. incomplete L5, L6--L7, incomplete sacrum, anterior caudal S l is shorter than the last lumbar and bears robust transverse vertebrae (Cdl-Cd4; Cd4 fragmentary),complete right and processes directed craniolaterally downwards. The prezyga left pelves with epipubic bones preserved on both sides, pophyses (in articulation with L7) are large and face dorso almost complete right and left hind limbs in anatomical caudally. The position of the first dorsal sacral fo ramen arrangement, with femora displaced medially; one posterior shows that S2 is much longer than Sl. The spinous processes caudal fo und in the same piece of rock. are broken, but it may be inferred fromthe long base of the pro cess preserved on Sl (Fig. 3A, B) that the sacral spinous Skull processes were apparently as large as those of the last lumbar Fig. l vertebrae. The transverse processes of S2 are longer than
The postcranial skeleton of Kryptobaatar (ZPAL MgM -Il41) those of Sl. Both articulate with the ilia, but when the described below was fo und in association with the skull and transverse process of the firstvertebra is covered by the ilium partial right dentary, which have not yet been figured. The dorsally, that of the second vertebra meets the medial side of 'basioccipital box' of Kielan-Jaworowska & Dashzeveg the ilium and is possibly less strongly synostosed to it. The (1978) (Fig. ID) was subsequently recognized as an artifact craniolateral corner of the first transverse sacral process is (Kielan-Jaworowska et al. 1986). The basicranial region of thickened to fo rm a rounded inflation, the very margin of Kryptobaatar does not differ from those of other taeniolabi which protrudes somewhat laterally and below, beyond the doid multituberculate genera. The skull is very large with ilium. The cranial margin of the second dorsal fo ramen is respect to the length of the body, its estimated length being preserved on the right side. The pedicles of the fused arches about 34 mm, which is about 1.1 times the length of the of the two first vertebrae arise dorsally, the laminae being pelvis. arranged horizontally, at a right angle to the pedicles. The intermediate sacral crest is developed as a continuous longi tudinal crest at the edge of the pedicle and the lamina. The Axial skeietan laminae, as seen in dorsal view (Fig. 3A, B) fo rm a trapezoid Figs. 2, 3, 6 shaped surface that narrows caudally. The median sacral Cervicalvertebrae (not figured).- The axis fragmentconsists crest was probably highest at the cranial part of S l. A poorly of a damaged body with bases of the arch on both sides. The preserved indentation is present in frontof an incompletely dens and postzygapophyses (caudal articular surface, zyga preserved spinous pro cess of S2. The preserved part of S4 pophysis caudalis, proc. articularis caudalis ) are missing. The consists of only a badly damaged fragmentof the arch and a bases of the transverse pro cess es are broken. The pedicles somewhat displaced postzygapophysis. F055IL5 AND 5TRATA 36 (1994) Anatomy and habits of multituberculates 7
Caudal vertebrae. - Cdl-Cd3 (Figs. 2, 3B-D), in articulation ilium to the end of the ischial tuber is 31.6 mm; when with a fragment of 54, were originally preserved above the measured to the most caudal prominence of the ischial arc it ischia. The length ofCdl, measured between pre- and post is 32.8 mm. The pelvic sutures appear to be synostosed, but zygapophyses is 4.3 mm, that of Cd2 4.3 mm. The transverse some of them are discemible: between the ischium and the processes are large and arise from the whole length of the pubis (between the acetabulum and the obturator fo ramen) bodies. The most complete is the lefttransverse process of on the medial aspect on both sides, and between the ilium Cd2, which is directed ventrally and twisted craniolaterally and ischium above the cranial margin of the acetabulum, at (in Fig. 3B it is almost completely preserved; it has been a point opposite the craniocaudal midpoint of the acetabu slightly damaged during the preparation and appears shorter lum. The area of the suture between the ischium and the in Fig. 3C.). Both pre- and postzygapophyses are large, the pubis below the obturator foramen is broken on both sides. cranial articular surface faces mediodorsally, the caudal The suture between the ilium and pubis is not discemible. lateroventrally. The pedides are lower than in the lumbar The ilium is 23 mm long. The wing of the ilium is rod-like vertebrae, and the laminae are arranged horizontally. The and reflectedlaterally at its cranial end. The estimated dis spinous processes are stout and very long, as those of the tance between the cranial ends of the ilia is 16 mm. The ilia lumbar vertebrae (see above); they arise from themiddle part are roughly oval in cross-section and expanded medially in of the laminae, that of Cdl is directed dorsally, Cd2 and Cd3 the area of the auricular surface (facies auricularis). Extend are somewhat indined and are extended longitudinally at the ing cranially fromthe acetabulum along the dorsal side of the extremities. The ventral aspect ofCd3 is partly exposed; there ilium, there is a weak ridge (much less prominent than in is no ventral crest. Nemegtbaatar) fo r the origin of the dorsal part of m. gluteus The single middle caudal vertebra (Fig. 3D) is exposed in medius. In lateral view the ilium increases in depth from the ventral view; its body is 7.4 mm long. The transverse pro acetabulum for about two thirds of its length to the caudal cesses arise from the whole length of the body and are ventral iliac spine, which forms a prominent process. Crani directed lateroventrally. There is a prominent ventral ally to the pro cess the depth of the ilium decreases again. median crest, and the surfaces between it and the extremities Along the ventral margin there are two concavities: in front of the transverse processes are strongly concave. and to the rear of the caudal ventrai iliac spine. The short cranial margin of the ilium is gently rounded. The wing in Pectoral girdle (forelimb unknown) frontof the auricular surface is concave. The shape of the auricular surface is not known, it is relatively long, extending Scapulocoracoid. - The right scapulocoracoid preserved in fo r 8 mm. The ventrai part of the ilium adjacent to the ZPAL MgM-I141 (Fig. SE-C) consists of an incomplete acetabulum is relatively small, blade-like and slightly con blade and a glenoid fossa. The scapular and coracoid parts of cave in lateral view. Although the suture between the ilium the glenoid fo ssa are arranged at an angle of about 120°with and the pubis is not preserved, there is an elevation (which
respect to each other. The suture between the glenoid and � may correspond to the suture) that extends fromthe aceta scapular parts is not discemible. As the Kryptobaatarscapu bulum and ends with the iliopubic eminence on the ventrai locoracoid is less complete than that of Nemegtbaatar ZPAL margin. MgM -I181 (see description of Nemegtbaatar below and Figs. The acetabulum is 3.4 mm long; as is characteristic of the 12 and 13G-J), in the description that follows we compare it multituberculates it is broadly and deeply emarginated dor with that of Nemegtbaatar. It cannot be stated with any sally, the articulated femoral heads being completely exposed certaintywhetherthe glenoid partwas L-shaped, as is charac dorsocaudally. The cranial rim of the acetabulum is highly teristic of Nemegtbaatar, but it is possible that the medially elevated, forming a rounded ridge. In frontof the cranial rim directed process was present. The arcuate ridge in the ventral a low, triangular protuberance extends for about 4 mm. part of the blade is not recognized. The cranial border is There is a small pit below the protuberance, dose to the possibly less prominent than in Nemegtbaatar, which may be acetabulum, in a place where in other mammals there is a due to the poor state of preservation of the Kryptobaatar tuberosity for the origin of m. rectus femoris. Caudally the scapulocoracoid. The infraspinous fo ssa appears to widen acetabulum is surrounded by an elevated border. Below this dorsally, as in Nemegtbaatar. 5ince there is a shallow fo ssa border there is a deep crescent -shaped notch on the ischium, cranial to the spine, it appears that Kryptobaatarpossessed an situated outside the acetabulum. The obturator fo ramen is incipient supraspinous fo ssa, which is, however, less obvious situated below and somewhat caudal to the acetabulum. It is than in Nemegtbaatar. The preserved part of the subscapular oval, elongated craniocaudally and 3.7 mm long. fo ssa is convex. The ischium, measured fromthe suture with the ilium to the end of the ischial tuber, is 8.6 mm long; measured to the Pelvie girdle and hind limb most caudal prominence of the ischial arc it is 9.8 mm long. Its dorsal margin is stronglythickened, fo rming a rounded Pelvis (Figs. 2, 3A, SA, 37D). - The length of the pelvis, ridge. It is sharply recurved dorsocaudally and fo rms a very measured on the right side from the cranial margin of the prominent ischial tuber. This, as originally preserved (Fig. 2) 8 Zofia Kielan -Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
Fig. 1. Kryptobaatardashzevegi (ZPAL MgM-I/41l, Djadokhta Formation, Bayn Dzak, Gobi Desert, Mongolia. DA. Incomplete right dentary, lateral view. DB. Medial view of A. De. Ventrai view ofincomplete skul! of the same individual. OD, E, F. Same skull as in C, in occipital, right lateral and dorsal views.
In D, on left side, missing ventrai wal! (dashed line) of presumable resonatory air space reconstructed. 1 = medial wal!s of air spaces fo rming the 'basioccipital box' of Kielan-Jaworowska & Dashzeveg (1978), recognized by Kielan-Jaworowska et al. (1986) as deformation artefact. A, B, D-F x2; C X4; D, E, F stereo-pairs.
Fig. 2 (opposite page). Kryptobaatar dashzevegi (ZPAL MgM-I/41), Djadokhta Formation, Bayn Dzak, Gobi Desert, Mongolia. Posterior part of skeleton found in association with skul! and dentary in Fig. I, consisting of: L5 (incomplete), L6, L7, damaged sacrum, Cdl-Cd3, almost complete hind limbs. DA.
Right lateral view. DB. Left lateral view. l = incomplete L5; 2 = L6; 3 = L7; 4 = sacrum, preserved in two parts; 5 = Cdl; 6 = postobturator notch; 7 = calcaneum, on leftside only the tuber calcanei has been preserved; 8 = parafibula;9 = astragalus; 10 = cuboid; 11 = groove fo rtendon of m. peroneus longus; 12 = hook like process of fibula; 13 = obturator fo ramen; 14 = epipubic bone; 15 = greater trochanter; 16 = lesser trochanter; arrow in A and upper arrow in B = left ischial tuber, right one not preserved; lower arrow in B = lateral mal!eolus of the fibula.Bone between distal en ds oftibia and fibulain A possibly fragment of dentary. Both x3.8. FOSSILS AND STRATA36 (1994) Anatomy and habits of multituberculates 9 10 Zofia Kielan -Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
Fig. 3. Kryptobaatar dashzevegi (ZPAL MgM-I/41). DA. Same specimen as in Fig. 2. afterremoval of fragmentaryS4 and Cdl-Cd3, dorsal view. Leftischial tuber seen in Fig. 2 broken offafter photographs in Fig. 2 were taken. DB. Same skeleton as in Fig. 2, dorsal view. Note high spinous process in L7 and long transverse process in Cd2. De. Part oflast sacral vertebra and Cd l-Cd3 ofskeleton in Fig. 2, afterbeing separated, dorsal view. Note that spinous and transverse processes appear shorter than in B, because of damage caused by preparation. OD. Single middle caudal vertebra fo und in the same piece of rock as the rest of the skeIeton, in ventraI view. l = L5; 2 = L6; 3 = L7; 4 = Sl; 5 = S2; 6 = parafibula; 7 = subtrochanteric tubercle; 8 = greater trochanter; 9 = Cd2, transverse process. A, x3; B, x l.S; C, D, X4; all stereo-pairs. FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 11 but now lost, was a roughlyparabolic process directed dorso (postobturator notch), recognized by Krause & Jenkins caudally that overhangs the caudal margin of the ischium (1983) as a postobturator fo ramen. The indentation in Kryp (ischial arc) dorsally. The latter is situated at an angle ofabout tobaatar lies within the fusedischiopubic symphysis, and if it 90° with respect to the dorsal margin. The lateral surface of is indeed a fo ramen, it would not open to the pelvic cavity, as the ischium is concave. To the rear of the obturator foramen characteristic also fo r other multituberculates (see 'Ana there is a prominence, parallel to the caudal margin of the tomical comparisons'). obturator fo ramen. The inner side of the ischium is slightly The pubis is relatively small, slightly concave in lateral concave. The two ischia are firrnlyfused to fo rm a prominent view. Below the obturator fo ramen it is fused ventrallywith keel (Figs. 2, SA) which extends fo r about 2 mm upwards its counterpart to fo rm a keel. On the cranioventral margin, from the ventral margin. Along the ventral margin of the dorsal to the junction with the epipubic (marsupial) bone, fused bones there is a distinct, but shallow, indentation there is an indentation, 0.7 mm long and 0.3 mm deep. The epipubic bone is 9.3 mm long, boomerang-shaped and slightly asymmetrical. In addition, its margins are fusiformat the extremities and arranged, in lateral view, subparallel to the ilium. In ventral view the epipubic bones meet the symphysis caudally and diverge cranially, which, however, may be due to the state of preservation. The most characteristic features of the Kryptobaatarpelvis are its narrowness, the strong degree of fusionof the ischia and pubes, and the strong fusion with the sacrum. The opposite pubes are directed steeplyventromedially and meet at an angle of about 40°; the ischia meet at 45° and progres sively open up to 80° at the ischial are. Femur (Figs. 2, 3A, B, 44A). - The femora preserved in acetabula have been pushed mediallyduring sedimentation, and when examined in dorsal view (Fig. 3A, B) they appear parasagittal. The right femur, which is undistorted, is 24.4 mm long. The head is placed on a cylindrical neck that fo rms Fig. 4. Diagram showing method of measurement of multituberculate an angle of about SO°with the shaft.The head is 2.8 mm wide vertebrae, exemplified by lumbar vertebra in left lateral (to the left) and in dorsal view, its articular surface being greater than a dorsal views. a = length of spinous process; b = distance between prezyga hemisphere. The fovea capitis femoris is not discernible. The pophysis and postzygapophysis; c = length of caudal margin of transverse greater trochanter (trochanter major) is very prominent, 3.4 pro cess; d = length of the body; e = distance between prezygapophysis and spinous process. mm long, projecting fo r about 1.2 mm beyond the head on
Fig. 5. Kryptobaatar dashzevegi(ZP AL MgM -I/41). DA. Same skeJeton as in Figs. 2--4,in ventrocaudal view, showing ventrai keel of ischia. DB, C. Partial right scapulocoracoid fo und in association with same skeleton in laterocaudal and craniomedial views. 1 = ventral part of infraspinousfo ssa; 2 = broken spine; 3
= subscapular fo ssa; arrow in B points to incipient supraspinous fossa. A x 1.5; B, C X4; A and B stereo-pairs. 12 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994) the leftside where it is bent, and fo r 1.7 mm on the right side. vided by a weak protuberance, directed mediocaudally to The extremity of the greater trochanter is recurved cranio craniolaterally, into two facets. The small medial fa cet, fo r medially. Its apex bears a rugose area for insertion of gluteal articulation with the medial femoral condyle, is arranged musculature (Simpson & Elftman 1928). This area is rela parallei to the above mentioned protuberance. The larger tively small, roughly crescent -shaped on the dorsal (cranial) lateral facet, fo r the lateral femoral condyle, is transversely aspect, delimited by a sharp crest that overhangs the shaft elongated and has an irregular proximal surface with a dis laterally. On the ventraI (posterior) aspect, the rugose area is tinct, transverse groove in the middle. Laterally it extends larger, roughly triangular, tapering distally. Its pointed end into a prominent hook-like process, which is triangular in merges distally (in lateral view) with a moderately prominent lateral view and overhangs the shaft laterally. It bears a facet gluteal crest. In dorsal aspect there is a subtrochanteric fo r the fibula on its caudal surface. The process is concave tubercle (see 'Terminology') and a small, elongated fo ssa from below, and in ventraI view a concave bridge of bone lateral to it. spans the distance between the pro cess and the proximal end The lesser trochanter (trochanter minor), as seen in latero of the tibia. The proximal articular surface extends caudally ventraI view, is veryprominent, 1.9 mm long and 1.9 mm well beyond the shaft. At the confluenceof the shaftand the wide, arising fromthe mid-width of the ventraI wall of the proximal articular area there is thus a broad, deeply concave shaft(n umber 16 in Fig. 2B, see also the femur ofNemegtba a fo ssa. A ridge of bone separates this fo ssa fromone adjacent tar, number 3 in Fig. 16A, C, fo r comparison). It fo rms a to it and beneath the aforementioned hook-like process. The plate-like, bent process, strongly protruding ventrally, con cranial (anterior) crest (margo cranialis, crista tibiae), be vex lateroproximally and concave mediodistally; in caudal cause of the caudal concavity of the proximal part of the view it has a hook-like profile. The lesser trochanter is not shaft, is comparatively sharp proximally, but it is poorly constricted at the base, and the neck, characteristic of? Eucos exposed as both tibiae are partly embedded in the matrix. modon (Granger & Simpson 1929), is not present. The cranial (anterior) tibial tuberosity (tuberositas tibiae) is The trochanteric (digital) fossa (fossa trochanterica) is hardly recognizable, although the cranial surface of the tibia small, roughlytriangular and poorly preserved; it prolongs as is convex. The shaft is compressed craniocaudally at the a narrow groove onto the greater trochanter. We designate middle of its length, its craniocaudal diameter is 2.1 mm, the the fissure-like fo ssa situated lateral to the lesser trochanter, transverse diameter l.S mm; in lateral view it fo rms agentle the post-trochantericfo ssa (referred to by Simpson & Elftman convex arch. 1928 and Krause & Jenkins 1983 as a caudal part of the The distal part of the right tibia is preserved; the medial divided trochanteric fo ssa; see 'Anatomical comparisons'). malleolus has been broken offand is preserved on the dorsal The post -trochanteric fo ssa appears to be shallower in Kryp surface ofthe astragalus (number l in Fig. 6A-C). A piece of tobaatar than in other genera, which may be due at least in the flat bone preserved between the distal parts of the tibia part to the state ofpreservation. The shaftis elliptical in cross and fibula (Fig. 2A) is possibly a displaced fragment of the section, dorsoventrally compressed, more convex dorsally right dentary. There is a transverse seam across the tibia, than ventrally, 2.8 mm wide and 1.9 mm deep in the middle separating the distal articular surface fromthe shaft,which of its length. might be at least in part a remnant of the boundary with the The boundary between the shaftand the distal epiphysis is epiphysis. recognizable, the latter being twisted slightly laterally with The lateral condyle and medial malleolus of the tibia are respect to the proximal epiphysis. The width of the distal less obvious than on the tibia of North Arnerican? Eucosmo epiphysis in dorsal view is 5.4 mm. The trochlea is shallow, don figuredby Krause & Jenkins (1983, Fig. 22; see also Fig. and the low trochlear ridges are arranged subparallel (rather 56E, F herein). The lateral condyle is large but not weU than obliquely) with respect to the shaft. There is a wide defined (see also 'Anatomical comparisons'). intercondyloid fo ssa (fossa intercondylaris). The lateral con Fibula (Figs. 2, 6C, 44A). - Both fibulaeare preserved almost dyle (condylus lateralis) is in dorsal view larger than the in anatomical position proximally, but slightly displaced medial one (condylus medialis ) and protrudes laterally over distally. The length of the leftone, which preserves the distal the shaft fo r 1.4 mm. In distal view the medial condyle is caudal tuberosity, is 17.2 mm. The fibulais situated lateral to wider than the lateral one; the width ofthe whole epiphysis in the tibia proximally, and more caudally in the distal part.The this view is 4.9 mm, the width ofthe lateral condyle is 1.9 mm head of the leftfibula is 2.4 mm wide in lateral view. It bears and of the medial condyle 1.9 mm (Figs. 2 and 3A, but see on its lateral side a prominent, triangular, hook-like process also the femur of Nemegtbaatar Fig. 17B-E, fo r comparison). (partly broken), that extends distally. Proximally on the The femur articulates only with the tibia; there is no femoro cranial wall of the process there is a flatfa cet articulating with fibularcontact. a large facet on the laterocaudal wall of the tibial head. Tibia (Figs. 2, 6C, 44A). - The right tibia is 18.8 mm long; its Posterior to the triangular process there is another small proximal epiphysis is verylarge, asymmetrical and 5.1 mm triangular process on the distal border of the head, directed wide in cranial view. The proximal articular surface is di- distally. In lateral view, the large triangular processes of the FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 13
Fig. 6. DKryptobaatardashzevegi (ZPAL MgM-I/41). DA, B. Incomplete right pes isolated fromskeleton inC, in dorsal and lateral views. DC VentraI view of skeleton in Fig. 2, before separation of right pes. OD. Leftpes of skeleton in C, with metatarsals placed horizontally. l = part of medial malleolus of tibia;
2 = part oflateral malleolus of fibula; 3 = calcaneum; 4 = cuboid; 5 = astragalus; 6 = navicular; 7 = L5; 8 = L6. Arrow in A and upper arrow in B = peroneal tubercle; two lower arrows in B = sesamoid bones. A, B X4; C x3; D x6; A-C, Stereo-pairs.
tibia and fibulaare aligned. On the caudal wall of the fibular the other on the caudal wall of the shaft.At the middle of its head there is a large facet fo r articulation with the parafibula length the shaftbecomes thinner and roughly parabolic in (preserved on the left side, see below). Extending distally cross section, compressed craniocaudally; it is 0.9 mm wide along the middle of the lateral wall of the shaft, beginning in lateral view. Distally the diameter of the shaftincrea ses. below the large triangular process, there is a rounded ridge The distal epiphysis is almost completely preservedon the with proximal concavities on both sides. There are sharp left side, and the lateral malleolus has been preserved (the short ridges bounding these concavities, one on the cranial, arrow in Fig. 2B). The middle part of the epiphysis is devel- 14 ZofiaKiel an-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994) oped as a rounded tuberosity, convex distally; this is sepa Calcaneum. - The calcaneum is about 4.6 mm long (right rated fromthe shaftby a transverse line that may correspond pes, Figs. 2A, 6A-C, 7 A-D, 54) and convex dorsally along its to the boundary of the shaftwith the epiphysis. On the right longitudinal axis.The robust tuber calcanei is late rally com side a part of the lateral malleolus has been broken offand is pressed. Its proximal end is slightly enlarged, irregular, and preserved laterally on the dorsal surface of the astragalus bears several small, poorly pronounced tuberosities. Extend (number 2 in Fig. 6A, B). ing obliquely along the dorsal surface of the tuber calcanei is a weak ridge that ends at the dorsal margin of the peroneal Parafibula.- The parafibulahas been preserved only on the tuberde. The peroneal tuberde, as preserved, fo rms a promi left side of ZPAL MgM-I141 (Figs. 2B, 3A, B, 44A). It is nent, sharply pointed triangular process, strongly protrud displaced laterally and arranged at an angle of about 125° ing obliquely laterodistally beyond the lateral margin of the with respect to the fibularshaft. The length ofthe osside is 3.2 bone (arrow in Fig. 6A and up per arrow in Fig. 6B). There is mm. It consists of a relatively narrow neck, 1.2 mm wide, and a weak ridge extending transversely across the peroneal tu a large, rounded muscular process. Along the middle of the berde. The poor state of preservation of the bone does not neck, there extend irregular grooves, roughly parallel to its allow us to state with any certainty whether the peroneal margin. The muscular process is concave at the contact with tuberde has been broken. As in all known multituberculate the neck and is inflated,but irregular, at the end; the inflated calcanea (Granger & Simpson 1929; Deischl 1964; Krause & part is 2.2 mm wide. The articular facet, which adheres to the Jenkins 1983; Szalay 1993; this paper Figs. 25, 55F-I, 56H-J) craniolateral surface ofthe fibular head,cannot be examined. this tuberde is rounded at the end, we presume that it has This parafibuladiffers from that ofPtilodus kummae (Krause been broken in Kryptobaatarand that its distal part is miss & Jenkins 1983, Fig. 23F) in having a more rounded and ing. This is whythe reconstruction ofthe peroneal tuberde in inflated muscular process, rather than one obliquely cut at Fig. 54 is based on better preserved North American multitu the end. berculate calcanea. However, the peroneal groove of Krypto baatar differsfrom that in ? Eucosmodon in being wider, and TARSUS AND PES Figs. 2, 3A, B, SA, 6, 7, 54, 59A in consequence the peroneal tuberde is shifted more later ally. In this respect, the calcaneum of Kryptobaataris remi On the right side all seven tarsal bones and fivemetatarsals niscent of the unidentified multituberculate calcaneum are preserved. The tarsal bones adhere tightly to each other fromthe Hell Creek Formation (Fig. 55E-G) and of a ptilo and are preserved in the original position, except fo r the dontid calcaneum fromthe Frenchman Formation (Szalay calcaneum that has been shiftedtransversely and the astraga 1993, Fig. 9.8). Although the calcaneum of Kryptobaatarhas lus which has been shiftedlaterally and in a plantar direction. been shifted laterally, it is evident that its distal margin As a consequence, the mediodistal rounded pro cess (referred (medial to the peroneal groove) articulated with the small to by Granger & Simpson 1929 and Krause & J enkins 1983 as facet on the dorsal side of the proximal end of Mt V. The the astragalar head; see 'Anatomical comparisons') has been medial part of the distal margin of the calcaneum possibly exposed. On the left side (Figs. 2B, 3A, B, SA, 6C-D) an articulated with a wide indentation on the lateral margin of almost complete tarsus, fivemetatarsals and all the phalanges the cuboid, proximal to the facet for articulation with Mt V. ofD Il-V, are preserved.Of the calcaneum only the tuber has The sustentacuIum was probably small, but the facet cannot been preserved; all other bones are in place, but the astragalus be examined. The astragalocalcaneal facet (proximal facet has been slightly displaced longitudinally and in a plantar for the astragalus, facies articularis talaris) is very large and direction, showing the mediodistal triangular process. The crescent-shaped but less prominent than in ?Eucosmodon astragalus contacts the navicular with its shorter (medio and in various calcanea figuredby Krause & Jenkins (1983, distal) margin. On both sides the tarsus and pes are strongly Fig. 26). Distal to it, there is a smaller cuboid facet, which was convex dorsally, possibly, at least in part, because of the state possibly situated more distally than in the unidentified of preservation. Therefore in Figs. 6 and 7 only a part of the North American calcanea. Between the astragalocalcaneal tarsus is visible in each view (see reconstruction in Fig. 54). facet and the peroneal tuberde there is a wide, shallow On the leftside, the tarsus and pes have been left asoriginally concavity, delimited distally by a faint ridge. Distal to this preserved and can be examined only in dorsal aspect. On the ridge the surface of the bone bends downwards. The plantar right side, afterthe photographs in Figs. 2 and 6C were taken, side of the Kryptobaatarcalcaneum cannot be examined. the tarsus and partial pes were separated fromthe rest of the specimen, but as the tarsal bones could not be separated, they Astragalus (talus). - Because of the oblique position of the can hardly be seen in plantar aspect (Figs. 6A, B and 7 A-D). astragalus in respect to the calcaneum (see reconstruction in The description of bones that follows, unless stated other Fig. 54), its margins are not oriented distally, proximally, wise, is of the dorsal (cranial) aspect. In Fig. 54 we give the laterally and medially, but rather medioproximally, latero reconstruction of the pes of Kryptobaatarbased on ZPAL distally, etc. The astragalus can be examined in both pedes in MgM -Il41 and on the tarsus of Chulsanbaatar ZPAL MgM dorsal (cranial) views, in the left pes also in a distoplantar I199b (Fig. 25). See 'Functional anatomy' for discussion of view and in the right pes in proximal and distal views (Figs. 2, the functionof the pes of Kryptobaatar. 6, 7). In the right pes, on the dorsal side, the medial malleolus FOSSILS AND STRATA36 (1994) Anatomy and habits of multituberculates 15
cuboideum astragalus naviculare astragalus
calcaneum
cuboideum
mesocuneiforme
entocuneiforme
c 1/1 11/ 11/ 11/ naviculare
naviculare -�� �"tIf!r'\;:- mesocuneiforme
entocuneiforme __�,...... :..;.L.... _
11/
Fig. 7. Kryptobaatar dashzevegi (ZPAL MgM-I/41), Isolated elements of skeleton in Fig. 2. DA-D. Camera lucida drawings of right tarsus and metatarsals. Fragments of distal ends oftibia and fibulapreserved on dorsal surface of astragalus, seen in Fig. 6A, B, are omitted. Roman numerals denote metatarsals. DA. Medial view. DB. Dorsal view. DC Dorsolateral view. DD. Lateral view. DE-G. DetaiIs of entocuneiform-Mt I joint, dorsal (slightly medial), mediodorsal and medial views. In F the navicuIar is omitted. Scale bars 2 mm.
of the tibia and part of the lateral malleolus of the fibulahave better seen in isolated astragali of an unidentified multitu been preserved (Fig. 6A-C). In dorsal aspect the astragalus berculate fromthe Late Cretaceous of North America (Fig. fo rms an irregular rectangle, arranged roughly laterodistally 55B--D) and ofPaleocene ?Eucosmodon sp. (Fig. 56C, D). In to medioproximally in the reconstructed pes. The medio proximal aspect the astragalus of Kryptobaataris roughly distal margin of the rectangular part is thickened. In latero triangular, with a rounded tip pointing in a plantar direction. distal view the rectangular part sends a rounded pro cess The astragalocalcaneal and sustentacular facets are not ex ('astragalar head'), situated more medially than laterally. posed on either side. The dorsal surface is relatively smooth, Along the cranial margin of this process there is a saddle especiallyin comparisonwith ?Eucosmodonsp. (Fig. 56C, D), shaped sulcus, which prolongs medially below the medio but both lateral and medial malleolar facets are recognizable, distal thickened end of the rectangular part and articulates the lateral large and gendy rounded, the medial much with the navicular. The details of the 'astragalar head' are smaller and more prominent. 16 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
Navicular (central tarsal bone, os tarsi centrale). - The na than in medial view. In medial view the plantar margin is 1.9 vicular (Figs. 2, 6, 7, 54) is a roughly rectangular bone, mm long, the dorsal margin is 1.4 mm, and the proximal preserved almost in place on both sides, although facing width is 1.5 mm. The entocuneiform fitstightly between the more medially than dorsally in the right pes. It is 1.8 mm navicular, mesocuneiform, Mt Il and Mt I and protrudes wide and 1.1. mm long alongthe medial margin. Its proximal somewhat over the medial side of the navicular. margin is incurved mediallyto articulate with the astragalus Metatarsals (ossa metatarsalia I-V). -N early complete meta (displaced on both sides); the distal margin is only slightly incurved in the middle. tarsals are preserved on both sides (Figs. 2, 5A, 6, 7, 54). Their lengths are: Mt I 5.4 mm, Mt Il 6.8 mm, Mt III 7.4 mm, Mt IV Cuboid (cuboideum, fo urth tarsal bone, os tarsale 4). - The 7.3 mm and Mt V 5.4 mm. In all the figures Mt V appears cuboid is exposed on both sides (Figs. 2, 6, 7, 54), but it is shorter than Mt I because of the oblique position of Mt V. Of particularly weU se en on the left side and has a somewhat the fivemetatarsals Mt V is the widest, Mt I the narrowest (in irregular shape (as in ?Eucosmodon, Granger & Simpson dorsal view), and the three medial are of subequal widths. Mt 1929, Fig. 23). It consists of a roughly rectangular body, Il - Mt IV are more expanded at their distal ends than which tapers proximally and is somewhat convex dorsally, proximally, but there is no distal groove. Mt I and Mt V are 1.8 mm long and l mm wide proximally. The distal width of expandedat the distal and proximal ends. Mt I has a distinct the cuboid is 1.6 mm. Distally the body sends a lateral medioproximal process and apparently also a lateroproxi transverse process which articulates with the medioproximal mal process, not weU exposed. Mt V has a lateroproximal facet of Mt V. The lateral side (exposed in the leftpes) distaUy prominence, but smallerthan in Mt L Mt V is shiftedproxi fo rms a deep concavity to receive the distal margin of the mallywith respect to Mt IV, and the medioproximal facet on calcaneum. Proximal to this concavitythere is convex facet Mt V articulates with the laterodistal facet ofthe cuboid. The fo r articulation with the cuboid facet ofthe calcaneum. In the proximal tip of Mt V fitsthe medial part of the distal margin right pes the distal margin of the calcaneum (although the ofthe calcaneum (which is displaced laterally and in a plantar calcaneum has been rotated), fitsthe lateral concave facet on direction). Mt V articulates with the peroneal tubercle and the cuboid. On both sides, the remaining tarsal bones fit fits with its proximal tip the peroneal groove. Similarly, in tightly to each other, and the facets fo r ectocuneiform, na Chulsanbaatar, in which the calcaneum has been somewhat vicular, and Mt IV are not seen. differentlydisplaced (Fig. 25), Mt V fitswith its proximal tip Ectocuneifo rm (lateral cuneiform, third tarsal bone, os tarsale the peroneal groove. We therefore believe that Mt V articu 3). - The ectocuneiform is preserved in anatomical position lated with the distal margin of the calcaneum, medial to the on both sides (Figs. 2, 6, 7, 54). It is a roughly rectangular peroneal groove in both taxa (see reconstruction in Fig. 54). bone, rounded proximally, slightly wider proximally than Mt I and Mt V have been preserved in both pedes slightly distally, 1.3 mm long and 0.5 mm wide distaUy. It snugly fits below the middle ones (in dorsal view). the navicular, cuboid, Mt III and mesocuneifo rm, although The joint between the entocuneiform and Mt I is almost of the facets for these bones cannot be recognized. hinge type and allowed extensive movements in the dorso piantar plane, with the possibility of only verylittle abduc Mesocuneifo rm (intermediate cuneiform, second tarsal tion. We have not found evidence for the opposability of Mt bone, os tarsale 2). - The mesocuneiform is roughly rect I (see 'Functional anatomi). angular, 0.8 mmlong and 0.8 mm wide in the middle, slightly wider distally than proximally, rounded at the corners (Figs. Sesamoid bones (Figs. 6B, 54B-D). - On the right side of 2, 6, 7, 54). It fitstightly between the navicular, ectocunei ZPAL MgM-I/4l the sesamoid bones have been preserved fo rm, entocuneiform and Mt V although its facets are not on the plantar side at the distal ends of all metatarsals except exposed. Mt L Entocuneifo rm (medial cuneiform, firsttarsal bone, os tarsale Phalanges (Figs. 2, 3A, B, 5A, 6C, D, 54). - The digits have 1). - The entocuneiform is the longest of the three cunei been preserved in the leftpes, but D Il is missing, only the fo rms. It notably protrudes over the distal margin of other metatarsal having been preserved. In D I and D III the ungual cuneiforms and is laterallycompressed (Figs. 2, 6, 7, 54). The phalanges are missing, while D IV and D V are complete. In distal surface is saddle-shaped in the dorsopiantar direction; D Il, Ph l is slightly damaged, but its length can be estimated, in the middle of the distal margins of the dorsal and plantar as Ph 2 and Ph 3 have been preserved in place. All the sides there are processes (the plantar longer) with a concavity phalanges are more expanded proximallythan distally and between them. As a res ult, in medial view the distal margin is taper distally. In D Il, Ph l and Ph 2 are 4.5 and 3.8 mm long, strongly concave (Fig. 7A, B, E-G). These processes embrace respectively. In D Ill, Ph l and Ph 2 are 5.1 and 2.8 mm the saddle-shaped proximal margin of Mt I, on which there respectively. In D IV, Ph l, Ph 2 and Ph 3 are 4.1, 2.7 and 1.3 are lateral and medial processes. The proximal margin is mm long. In DV, Ph l,Ph2and Ph 3 are 3.1, 2.5 and 1.3 mm slightly concave. In dorsal view the entocuneiform, as pre long. The ungual phalanges are pointed and roughly served, is oriented obliquely dorsomedially and is narrower rounded in cross section. FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 17
Genus Nemegtbaatar Kielan- process is peg-like, about 2.2mm long, and is rounded at the J aworowska, 1974 end. The caudal articular fovea is roughly oval, slightly nar rowing ventrally, almost flat;its longer diameter is 2.0 mm. Kielan There is a small fo ramen (about 0.2 mm in diameter, num Nemegtbaatar gobiensis ber 9 in Fig. 8B, C) situated dorsal to the caudal articular Jaworowska, 1974 fovea and a corresponding foramen situated laterodorsally Figs. 8-13, 14A, 15, 16, 17B-1, 28C, 30B, 34A, 35, 36B, 37 A, 39-43, 45, 47, to the cranial articular fovea. Both are apparently toa small to 50, 61 transmit the arteria vertebralis and possibly are vascular Material. - Red beds of Khermeen Tsav, Khermeen Tsav Il, foramina (see 'Anatomical comparisons'). In ZPAL MgM -1/ ZPAL MgM-II81: skull associated with dentaries, fragment 82 (Fig. 8D; see also Kielan-Jaworowska et al. 1986, Fig. 18) of Cl, C2-C4, ?L2-L7, Sl, damaged S2, S3 and S4, fragments an incomplete atlas, lacking the ventral arch and the trans of ribs, ventral part of the right scapulocoracoid, proximal verse processes, is broken into several pieces and was not part of the right humerus and, separately, its damaged distal separated fromthe skull. part, proximal part of the left ulna with broken olecranon Axis. - In ZPAL MgM-I/81 (Fig. 10) the axis (without the associated with a proximal part ofthe radius, distal part ofthe dens) is 2.8 mm long and in ZPAL MgM-I182 (Fig. 8F, 9) 1.3 right radius associated with the ?scaphoideum and ?lu mm long. The base ofthe dens is in ZPAL MgM -II82 about natum, two isolated carpal bones (?triquetrum and displaced lA mm wide and 0.9 mm deep. The body is strongly com ?pisiform, ?trapezoideum or ?praepollex), an incomplete pressed dorsoventrally. pelvis, the proximal part of the right femur, and the middle The cranial right and left articular surfaces are confluent part of the shaftof the leftfe mur. ZPAL MgM -II82: skull of with each other and fo rm, in ventral view, a crescent -shaped a juvenile individual, both dentaries, a damaged atlas, C2- area that strongly protrudes ventrally; in ZPAL MgM-II82 C7, Tl-T 4, rib fragments.ZP AL MgM- 1/110: the leftfe mur the ventral part of the body to the rear of this area is partly in two pieces, the distal part, in anatomical articulation with damaged. The ventral crest is prominent and widens both the tibia and fibulaand a fragmentof a ?parafibulapreserved cranially and caudally. The depressions lateral to the crest are in the knee joint. ZPAL MgM-I/1lO is smaller than ZPAL deep, especially immediately behind the cranial articular MgM -1/81 but possibly corresponds to the size of a juvenile surfaces, and are pierced by numerous nutrient foramina. ZPAL MgM -II82. The assignment of ZPAL MgM -1/1 10 to The transverse processes are broken offin both specimens, N. gobiensis is tentative, based on size and on the fact that but their bases are wellpreser ved in ZPAL MgM -I181. As in Nemegtbaatar is the only multituberculate of such a size in all the cervicals, the transverse processes arise by two roots: a the Barun Goyot Formation. ventral one fromthe body, visible in ventral view as a promi nent oblique crest, and a dorsal one from the arch. The Skull transverse canal is present; it is open ventrally on both sides Figs. 8A, D ofZPAL MgM -II81 because of the damage; a fragmentof the cervical rib (see below) has been preserved on the right side. The skull of Nemegtbaatar was described by Kielan-Jawo The postzygapophysisis large, directed cranioventrally. The rowska (1974), Kielan-Jaworowska etal. (1986), and Hurum dorsal side of the body is flat,perforated by one or two pairs (1992, 1994). In ZPAL MgM-II81 its estimated width is 31 of nutrient forarnina. The arch is preserved in ZPAL MgM- mm, the estimated length is 40 mm, which corresponds to 1/81, the pedicles are moderately high, and the laminae arise 1.15 of the estimated length of the pelvis. obliquely dorsomedially above the posterior part ofthe body and the postzygapophysis. The laminae are more stout at the Axial skeleton base than upwards, roughly parallel-sided, about 3.9 mm long at their longitudinal midpoint. At the point where right CERVICAL VERTEBRAE AND CERVICAL RIBS and leftlaminae meet, the length of the arch increases insig Figs. 8B-F, 9, 10 nificantly. At the top there is a broken surface, fo rming the In ZPAL MgM-II82 C2-T4 are preserved together, and the base of the spinous process, which, judging fromthe size of whole set is bent dorsally. In ZPAL MgM -1/81, C2, C3 and C4 the arch and preserved broken surface, appears to have been are in succession but are separated fromeach other. Between relatively small. The vertebral fo ramen as preserved in ZPAL C2 and C3 a short piece of bone separating the two bodies is MgM -I182 was relatively high, distinctly narrowing dorsally. preserved in the position of an intervertebral disc. C3-C6 (Figs. 8E, 9, 10). - The body of C3 is slightly less Atlas (Fig. 8B--D).- In ZPAL MgM -I181 a fragmentof a right compressed dorsoventrally than in C2; the degree of dorso side of the atlas, with cranial and caudal articular foveae and ventral compression of the successive vertebrae gradually a transverse pro cess, is preserved (Fig. 8B--C). The cranial decreases caudally along the vertebral column. The body of articular fovea is roughly oval, concave, narrowing dorsally; C3 (in ventral view)is 2.2 mm long in ZPAL MgM -II81 (Fig. its longer diameter measures about 3.3 mm. The transverse 10) and 1.7 mm long in ZPAL MgM-I182 (Fig. 9), C4 and C5 18 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
Fig. 8. Nemegtbaatar gobiensis. DA-C. ZPAL MgM-I/81, Red beds of Khermeen Tsav, Khermeen Tsav 11, Gobi Desert, Mongolia. DA. SkuI! and incomplete skeleton as fo und, afterpartial preparation; fragmentsof damaged ribs not marked by numerals are also seen. DB, C. Right side of atlas of individual in A, caudal and cranial views. DD-F. ZPAL MgM-I/82, horizon and locality as in A. OD. Skull and atlas ofjuvenile individual in ventrai view. DE, F. Cervical and thoracic vertebrae ofindividual in D, ventrocaudal and cranial views. l = dentaries (only posterior border of/eftone is seen); 2 = anterior part of right ilium;
3 = proximal part ofright fem ur; 4 = distal part ofleftfe mur, epiphysis ofwhich was lost during preparation; 5 = anterior part of/eftilium seen in cross-section;
6 = L3; 7 = Sl; 8 = damaged 52-54; 9 = ?vascular fo ramen; 10 = atlas; 11 = axis with broken dens; 12 = Tl; arrow in E points to firstleft thoracic rib. A X1.5; B, C x8; D x2; E, F x4; B and E stereo-pairs. FOSSlLS AND STRATA 36 (1994) Anatomy and habits of multituberculates 19
Fig. 9. Nemegtbaatar gobiensis (ZPAL MgM -1/82). DA-C. Cervical and firstthoracic vertebrae C2-T4 ofindividual in Fig. 8D-F, leftlateral, ventral and right lateral views. Matrix with bone fragmentsseen on leftside of specimen (right side in photographs) in Fig. 8E and F has been removed. OD. Middle part of same specimen in oblique lateroventral view. l = fo urth cervical rib; 2 = axis; 3 = firstthoracic vertebra; 4 = firstleft thoracic rib; arrow in D = groove for arteria vertebralis (transverse canal). A-C x4; D x8; all except C are stereo-pairs.
in ZPAL MgM-I/82 are 1.7 mm long each, C6 1.9 mm. The width of the bodies in ZPAL MgM-l/82 (Fig. 9) are: C3 3.8 mm, C4 3.8 mm, C5 4.2 mm and C6 3.2 mm. The bodies of C3-C4 are roughly rectangular, those ofC5-C6 are gradually more trapezoidal, their cranial diameters becoming wider in relation to the caudal diameters. The ventral crest on C3 is less prominent than on C2, but on successive vertebrae it becomes more prominent up to C6. The depressions lateral to the crest are shallower on C3-C6 than on C2. The ventral branch of the transverse process on all the cervicals is promi nent, but true inferior (ventral) lamellae are not developed (Howell 1926; see also Kielan-Jaworowska 1977). On C3 the ventral branch extends obliquely along almost the whole length of the body; on the successive vertebrae it is gradually shorter, and on C4-C6 it is confinedto the firsttwo-thirds of the body length. The base of the dorsal branch of the trans verse process is shorter than the ventral one and arises on all Fig. lO. Nemegtbaatargobiensis (ZPAL MgM-I/81). DA. Cervical vertebrae the vertebrae below the most caudal part of the prezygapo C2-C4 of individual in Fig. 8A, ventral view. DB. Same specimen in left physis. The transverse processes are broken offat various lateral view. l = depression lateral to ventraI crest; 2 = ventraI root of transverse process ofaxis; 3 = ventral root oftransverse processes ofC3 and levels on all the vertebrae, except for the right side of C4 in C4; 4 = fragmentof broken cervical rib; arrow in A = groove for arteria ZP AL Mg-Ml/82, where the cervical rib (see below) has been vertebralis (transverse canal). Both X4; A stereo-pair. 20 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994) preserved. Although the transverse processes are broken, the as broken offheads of the first ribs, cementedto the cranial gro ove fo r the arteria vertebralis and its accompanying vein costal foveae. If so, the cranial costal foveae were large, fa cing (part of the transverse canal) is clearly seen between the bases mostlyventrally. The caudal costal foveae are hardly discem oftheventral anddorsal branches of the transverse processes. ible on either side, possiblyvery small. The transverse process The pre- and postzygapophyses are well preserved on both is single-pronged, imperforate and arises opposite the most sides of almost all the cervicals in ZPAL MgM-I/82 and less cranial part of the vertebral body (ventral view). On the left completely in ZPAL MgM-I/8l. They fo rm large oval sur side, the costal fovea of the transverse process is preserved in faces arranged obliquely cranioventrally. The relatively nar articulation with the first rib, facing ventrocaudally. The row laminae arise dorsomedially and slightly above the post prezygapophysis is broken offon the right side and damaged zygapophyses. In C3 and C4 the arches are of alm ost the same on the left. The postzygapophysis is very large, directed length all along their height, whereas in CS-C6 their diam obliquely cranioventrally, as on the cervical vertebrae. The eters decrease dorsally. On C6 there is a tubercle at the point lamina arises obliquely dorsomedially above the postzyga where the left and rightlaminae meet. T races of the tubercles pophysis; its length decreases upwards. There is a tubercle at are also present on the anterior cervicals. From C2 to C7 the the top of the arch. The arch is slightly lower than on C7 and laminae become gradually more horizontally arranged and the anterior cervicals. the vertebral fo ramen becomes lower. T2 is similar to Tl, its body being 2.2 mm long and 3.6 mm wide. The arch is lower than in Tl, the laminae being ar C7. - The body ofC7 in ZPAL MgM-I/82 (Fig. 9) is 2.0 mm ranged more horizontally than vertically, with a small tu long and 2.9 mm wide, trapezoidal and generally similar to berde (spinous process) on the top. that of C6. The broken-offventral branch of the transverse The bodies of the consecutive thoracic vertebrae T3 and pro cess is preserved on both sides and extends obliquely T 4 become gradually more compressed laterally and longer; from andalong little more than a half of the body length. The T3 is 2.3 mm long and 3.6 mm wide, T4 (damaged) is in dorsal branch is shorter than the ventral one, broken on the caudal viewroughlytriangular, taperingventrally, with small right side, but preserved on the left side as a triangular caudal costal foveae at the dorsolateral corners. On T3 the process directed dorsocaudally, overlapping ventrally the caudal costal foveae are partly seen, and the cranial costal transverse pro cess of Tl. There is a distinct longitudinal foveae on both vertebrae are poorly recognizable. The arch, groove between the dorsal and ventral branches of the trans preserved only on T3, is low, the laminae being arranged verse process, although it is shallower and less distinct than on the preceding vertebrae. We therefore condude that the almost horizontally. There is a dorsal tuberde and minute 'processes' on the caudal margin. Otherwise the two verte transverse process was perforated by the transverse foramen. brae do not differ fromthose of Tl and T2. The caudal costal fovea is not recognizable on C7 with any certainty. Thoracicribs (Figs. 8E, 9B, C). -The proximal part ofthe first Cervical ribs. - In ZPAL MgM-I/81 a broken part of an leftrib in ZPAL MgM -I/82 (the arrow in Fig. 8E) is arranged apparent cervical rib has been preserved on the right side of longitudinally along the lateral side of the bodies of Tl and the axis (number 4 in Fig. 10). The dorsal branch of the T2. The head is cemented to the cranial costal fovea of Tl, transverse process has been preserved on C3, and both dorsal and the neck (displaced) articulates with it, while the dis and ventral branches are preserved on C4 and CS on the right placed tubercle articulates with the costal fovea of the trans side in ZPAL MgM-I/82 (Fig. 9A, B, D). In all these cases the verse process of Tl. In addition to the heads of the right first transverse processes end with distinct, rounded articular and second ribs cemented to the respective costal foveae in surfaces for the cervical ribs. The damaged rib has, however, the same specimen, numerous broken rib fragments are been preserved only between C4 and CS and apparently preserved in ZPAL MgM-I/8l. belongs to C4; because of its poor state of preservation (it appears to be pointed cranially rather than caudally) it can LUMBAR VERTEBRAE not be excluded that this is the rib of CS which has been Figs. BA, 11, 34A, 35, 36B, 39B, 40B turned around. The preserved part of the cervical rib shows We tentatively accept that there were seven lumbar vertebrae that it was possibly relatively large, roughly oval in lateral in Nemegtbaatar, the first one not being preserved. The Vlew. arches, when seen in cranial and caudal views, form a low rectangle. The pedides are strongly concave laterally but are THORACIC VERTEBRAE AND RIBS vertically expanded. On the boundary between the pedicle Thoracic vertebrae (Figs. 8E, 9). - The body of Tl in ZPAL and lamina there is a prominent intermediate crest, devel MgM -I/82, is in ventral view, similar in outline to that of C7, oped as an edge, concave in the middle, that extends between 2.2 mm long, roughly rectangular, 3.3 mm wide. The middle the lateral margins of the pre- and postzygapophyses. On the part of the body protrudes ventrally. The ventral crest is concave surface of the pedide, below the intermediate crest missing. At the craniocaudal corners ofthe bodythere are, on there is a weaklongitudinal ridge, convex dorsally, that is well both sides, what appear to be 'tubercles' which we recognize preserved only on the right side ofL4 and LS. FOSSILS AND STRATA 36 (1994) Anatomy and ha bits of multituberculates 21
Fig. 11. Nemegtbaatar gobiensis (ZPAL MgM-I/8I). DA. Lumbar vertebrae L2-L7, firstsacral vertebra and broken part ofleftilium of individual in Fig. 8A; dorsal view. DB. Same in left lateral view (ilium removed). l = L2; 2 = L3; 3 = Sl; 4 = leftilium (broken); upper arrow in A = origin ofm. sacrocaudalis dorsalis; lower arrowin A = origin of m. semispinalis dorsi. Both X4; A stereo-pair. 22 Zofia Kielan-Jaworowska & Petr P. Gambaryan F055IL5 AND 5TRATA 36 (1994)
The prezygapophysisis oval, large and faces dorsally and an intlation,similar to that in Kryptobaatar.This intlationfits medially; the postzygapophysis is rounded and faces ven in shape and size with the cranial part ofthe auricular surface trally and laterally. Both pre- and postzygapophysis are preserved on the ilium. It is impossible to state whether two slightly more massive on the posterior than on the anterior sacral vertebrae (as in Kryptobaatarand Chulsanbaatar) ar lumbar vertebrae. There is no metapophysis (proc. mamil ticuIated with the ilium. It seerns,however, that, as in Krypto laris). The anapophysis (proc. accessorius) is also laeking, baatar, the ilium covered the transverse proeesses of the but on the lateral sides of the pedicles on L4 and L5 (less sacral vertebra (or vertebrae) dorsally. The deep incisure on certain on L3) there is a longitudinal lip in the place where an the base of the transverse proeess, preserved on the leftside, anapophysis occurs in other mammals, e.g., Tachyglossus, shows the position of the relatively large first dorsal sacral most marsupials, insectivores, carnivores and others. The foramen. In ventral aspect 51 is relatively tlat, inasmuch as spinous pro cesses are more or less broken offon all the the median ventrai crest is laeking,developed only as a very lumbar vertebrae near their bases, because of the damage faint ridge. Moreover the transverse proeesses are contluent done by preservation and preparation. It appears fromthe with the body. preserved parts (Fig. Il) and the preliminary drawings made Only a small anterior fragmentof the left side of 52 has before the preparation, that the spinous proeesses shift in been preserved (Figs. 8A, 16G, H), showing the relatively position and change shape fromL2 to L6 and were very long, large (although broken) spinous pro cess, the proximal part as reconstructed in Fig. 36B2• On the firsttwo lumbars they of the transverse proeess with the caudal margin of the first are relatively small, arising fromthe cranial part of the arch dorsal sacral foramen, and the fragmentof the vertical wall of and sloping cranially and dorsally. Caudally they become the leftlamina. As the caudal part of52 and the cranial part of gradually more massive and more dorsally oriented. On L2- 53 are missing, it is impossible to estimate the length of52. In L5 there is a trianguIar surface that slopes caudally and Kryptobaatar52 is longer than 5 l, and this was probably the downwards fromthe base of the spinous pro cess and widens case in Nemegtbaatar. The transverse proeesses of both 53 caudally. It is limited by lateral ridges that extend to the and 54 are missing, only the bodies and the arches (without medial margins of the postzygapophyses and has a median spinous proeesses) being preserved. 5ince 53 is broken, its ridge. This ridge extends dorsally along the midline of the length cannot be given; that of54 is 5.4 mm. The pedicles of spinous proeess. On consecutive vertebrae this surface be the fusedarches of 53 and 54 arise dorsally, the laminae are comes more ventrally oriented, aligned completely ventrally arranged horizontally, and the intermediate sacral crest is on L7. rounded. The roots of the broken spinous proeesses arise The transverse proeesses (Figs. 8A, Il, 34A, 35, 36B, 39B, fromthe caudal part of the vertebrae. The right postzygapo 40B) are relatively tlatand very large; they extend cranio physis of 54 is preserved and is large and rounded, the lateroventrally and become broader towards L7. The com articular surface being arranged horizontally. The ventral plete left transverse pro cess of L5 and the right one of L7 sides of the bodies of 53 and 54 are partly exposed. There is a show that their extremities are extended longitudinally and prominent ventral crest, which widens at the caudal end of project cranially as distinet proeesses, with a minute tuber 54. At the longitudinal midpoint of 54, the crest widens and like thickening at the craniolateral corners. bears a longitudinal concavity. The sides of the bo dies lateral It was possible to expose the ventral surface ofL2 only. The to the crest are concave. The caudal epiphysis of the body of length ofthe body is 5.1 mm, and there is a prominent ventral 54 is slightly concave, arranged slightly obliquely ventro crest, partly broken. The body lateral to the crest is strongly caudally. concave. In cranial aspect the body ofL2 is 3.9 mm wide and is truncated ventrally. Pectoral girdle and fo relimb Scapulocoracoid (Figs. 12, 13G-J, 28C). - A ventral fragment 5ACRUM Figs. 8A, Il, l6G, H, 39A of a right scapuIocoracoid is preserved in ZPALMg M-I/81; the matrixhas not been removed fromthe infraspinousfo ssa Anincomplete sacrum has been preserved in ZPAL MgM -Il and fromthe base ofthe acrornion becauseof the fragilestate 81. 51 (Figs. 8A, ll) is in anatomical position with L7 and of the bone. The infraspinous fossa is only partly preserved separated from52; its body is shorter and wider than those of and apparentlywidens dorsally. The glenoid fo ssa, the caudal the lumbars. The spinous process is broken; the preserved border of which is partly missing, is pear-shaped. The cora part shows that it was apparently as large as on the lumbars. coid and scapular parts fo rm a broad angle of approximately The transverse proeess is much shorter transversely and 120°. The coracoid part is asymmetrical, L-shaped in cranial thicker than on the lumbar vertebrae; it is directed laterally and caudal views, its ventrai extremity being expanded medi and slightly ventrally. The transverse proeess appears to be allyto produee a prominent, rounded proeess. The coracoid relatively narrow, as preserved, but its caudal parts have been suture is recognized on the basis of a calcite-filledseam that broken offon both sides. On the left side, the craniolateral runs across the glenoid fossa. Along the cranial surface ofthe corner of the transverse proeess is well preserved and bears coracoid there is a rounded ridge with a min ute tubercle. FOSSILS AND STRATA 36 (1994) Anatomy and ha bits of multituberculates 23
ventrally, slightly cranially, parallel to the ridge on the outer surface of the glenoid fo ssa. At the cranioventral end of the spine, on the ventral edge of the scapulocoracoid there is a depression (number 12 in Fig. BI).
fossa supraspinata Humerus(Figs. 13A-E, 3IB). -The proximalpart ofthe right fossa humerus preserved in ZPAL MgM-I/81 (Fig. 13A-E) is ro infraspinata bust. As is characteristic of multituberculate humeri, the --'--::44-�--- spina scapulae greater tuberde (tuberculum majus) is higher and lies doser to the head than does the lesser tuberde (tuberculum mi nus). The intertubercular (bicipital) groove (sulcus inter tubercularis) is deep, especially on the side of the greater acromion tuberde. It narrows slightly distally and then widens again. The posterior crest, running in proximal prolongation ofthe ectepicondylar flange to the head (Kielan-Jaworowska & Dashzeveg 1978) is not very prominent. As is also character istic of multituberculate humeri, the head overhangs the shaftdorsally and the crest of the lesser tuberde ( teres tuber Fig. 12. DNemegtbaatar gobiensis (ZPAL MgM-I/Sl). Camera lucida draw osity, tuberositas teres major) is crescent-shaped, not very ing of right scapulocoracoid of individual in Fig. SA (see also Fig. l3G-J), prominent (number 5 in Fig. 13B, D). The damaged distal lateral view. Scapular spine broken, and ventraI part ofacromion (seen in Fig. l3G-J) is not shown. Scale bar 5 mm. fragmentof the same humerus does not show characters that would differentiate it from other multituberculate humeri (see distal end of the unidentifiedmultituberculate humerus fromthe Hell Creek Formation, Montana, figuredfor com This ridge continues for a short distance on the scapula as the parison in Fig. 14B). The entepicondylar region of the cranial border, although it is less prominent. Beyond the Nemegtbaatar humerus, showing uncertain musde scars, is cranial scapular border the ridge continues dorsally as a very figured in Fig. 30B. Of all the proximal multituberculate sharp keel, strongly reflectedlaterally on the dorsal end. humeri known (see Krause & Jenkins 1983 and Kielan The shoulder blade (Fig. 13H-J) is narrow and relatively Jaworowska & Dashzeveg 1978 for reviews), the humerus of flatventrally. A weak thickening extends on the blade along Nemegtbaatarresembles that of a taeniolabidoid, fam., gen. the cranial border and another one longitudinally along the et sp. indet. (ZPALMgM-I/165) from theDjadokhta Forma highest convexity of the blade, on the subscapular fossa. tion (Kielan-Jaworowska 1989). The Nemegtbaatar hu Dorsally the blade widens and becomes convex. The sub merus is only slightly smaller than ZPAL MgM-I/165 and scapular fo ssa is convex, except for the part lying along the differs fromit in that the humeral head is somewhat higher keel of the cranial border, where there is a small concavity and more rounded, the intertubercular gro ove is not as deep (number Il in Fig. BI, J). The caudal margin just above the and the deltopectoral crest less prominent. It is larger and glenoid fo ssa is gently incurved. On the ventral part of the more robust than in Tugrigbaatar (Kielan-Jaworowska & medial side of the blade, lying in prolongation of the coracoid Dashzeveg 1978), but much smaller and less robust than that edge, there is a ridge that extends in an arch towards the of?Lambdopsalis (Kielan-Jaworowska & Qi 1990). Also the ventral margin (number 13 in Fig. BH). The ridge is more teres tuberosity (not preserved in ZPAL MgM-I/165), in prominent ventrally than dorsally, with a shallow pit behind Nemegtbaatar is less prominent than in ? Lambdopsalis. it, just above the glenoid fo ssa. The craniolateral part of the blade is incomplete (Figs. 12, Radius and ulna (Figs. 13F, 14A). - A partial leftulna with a BI), but the matrix preserved in the caudal dorsal part broken olecranon and missing the distal extremity has been apparently corresponds to the shape of the missing bone. preserved together with the proximal part of the radius in The preserved part ofthe spine is short, limited mostly to the ZPAL MgM-I/81 (Fig. 14A). The ulna is strongly com ventral part of the scapula, and has a wide base. Dorsally it pressed laterally; its mediolateral diameter at the level of the was confluentwith the missing caudal margin of the cranio radial head is 1.0 mm, and the dorsoventral diameter is 1.9 lateral blade, thus the spine as a whole is arranged obliquely mm. The ulnar shaftslightly decreases in craniocaudal diam across the blade. The dorsal part of the craniolateral blade eter distally and becomes roughly triangular in cross section. between the keel of the cranial border and the dorsal pro Along the medial side of the shaft thereextends a longitudi longation of the spine is concave and is recognized here as an nal fo ssa, bordered by a prominent crest fo r the interosseus incipient supraspinous fo ssa (Figs. 12 and number 9 in Fig. ligament. See also the proximal part ofan unidentifiedmulti 131). The spine extends ventrally, turning slightly caudally tuberculate ulna fromthe HellCreek Formation, Montana, and continues as a peg-like acromion process; this is oriented figuredfo r comparison (Figs. 14C-E, 32B, 33B). 24 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA36 (1994) FOSSlLS AND STRATA 36 (1994) Anatomy and habits of multituberculates 25
Fig. 14. DA. Nemegtbaatar gobiensis (ZPAL MgM -1/81). Proximal part ofleftradius and ulna (olecranon broken) of individual in Fig. 8A, lateral view. Cranial margin of radius shiftedslightly medially; caudal margin of ulna also shiftedmedially. DB. Distal part of left humerus of unidentified multituberculate (AMNH 118267), ventrai view, Bug Creek Anthills site, Hell Creek Formation, Montana. OC, D, E. Left ulna of unidentified multituberculate (AMNH
118505), horizon and locality as in B. Proximal part in medial, cranial and lateral views. l = articular circumference; 2 = tuberosity for insertion of m. biceps brachii; 3 = ulnar condyle; 4 = radial condyle; 5 = entepicondylar foramen; 6 = articular surface for ulnar condyle; 7 = radial notch. A x6; B-E X4; all except C stereo-pairs; all coated with ammonium chloride.
Fig. 13 (opposite page). Nemegtbaatar gobiensis (ZPAL MgM-I/81). Iso On the proximal part of the radius (Fig. 14A), there is a lated parts of skeleton in Fig. 8A. OA-E. Proximal part of right humerus. roughly semilunar, obliquely directed medial facet (articular DA. Lateral view. DB. Dorsal view. De. Proximal view. OD. Medial view. circumference, circumferentia articularis), fo r articulation DE. Ventral view. OF. Distal part of right radius, associated with incom plete scaphoideum (to the right) andlunatum, in cranial view. OG-J. Right with the ulna. Distal to that facet there is a triangular tuber scapulocoracoid. OG. Ventrai view. OH. Craniomedial view. DI. osity fo r furthercontact with the ulna, medial to which there Craniolateral view. OJ. Cranial view. l = greater tubercle; 2 = lesser extends a gro ove for muscular insertion (see 'Myological tubercle; 3 = deltopectoral crest; 4 = posterior crest; 5 = teres tuberosity; 6 reconstructions'). The shaft is craniocaudally compressed. = intertubercular groove. 7 = glenoid fossa; 8 = acromion; 9 = incipient The radial head is mediolaterally elongated; its medio lateral supraspinous fo ssa; 10 = ventrai part ofthe spine; 11 = subscapular fo ssa; 12
= origin ofm. infraspinatus; 13 = ridge for fourth (most cranioventral) diameter is 1.7 mm, and the diameter of the ulna at the level aponeurosis of m. subscapularis; arrows in G and H point to infraspinous of the radial head is 2.3 mm. fossa, filledwith matrix. All X4; stereo-pairs. 26 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
The distal end of the right radius has been preserved together with two carpal bones, exposed in cranial view in ZPAL MgM-I/81 (Fig. 13F). The middle part of the shaftof the radius is 1.3 mm along the craniocaudal axis and 1.9 mm along the transverse axis. The shaftwidens strongly distally, and the distal epiphysis is 3.3 mm wide. Along the cranial side of the shaft thereextends a longitudinal groove that narrows distally. On the distal end of this gro ove is a longitudinal crack. The distal epiphysis is distinguished from the shaft owing to the deeply excavated suture between the two areas. It bears a prominent, triangular styloid process. The caudal Fig. 15. Nemegtbaatar gobiensis (ZPAL MgM-I/8l). Isolated right carpal bones, in oblique distal view, of skeleton in Fig. 8A. l = ?triquetrum; 2 = side of the radius is concave. In the same piece of rock displaced ?pisiform, ?trapezoideum or ?praepollex. Stereo-pair; x8. fragments of broken metacarpals (not figured) have been preserved. Carpus. - ?Right scaphoideum (radial carpal bone) and caudal ventral iliac spine. The auricular surface consists of a lunatum (semilunare, intermedial carpal bone) have been large, rounded caudal part that projects ventrally, fo rming preserved in association with the above described radius of the medial wall of the caudal ventral iliac spine, and a smaller ZPAL MgM-I/81 (Fig. 13F), exposed in cranial view. The cranial part separated fromthe caudal one by a weak vertical scaphoideum is damaged, roughlyoval, elongated proximo ridge. The caudal part is delimited posteriorly by a distinct distally and situated distal to the styloid process (possibly vertical ridge. The line delimiting the gluteal surface dorsally slightly displaced laterally). The lunatum is much smaller, fo rms a sharp ridge (much more prominent than in Krypto roughly circular and situated distal to the lateral part of the baatar) that extends caudally to a notch in front of the radius. acetabulum. The boundary between the body of the ilium Two isolated carpal bones (Fig. 15) have been preserved and the pubis cannot be recognized with any certainty. It within one piece of rock, some distance from the radius possibly extends above the sharp ridge that runs cranially described above. They are tentatively identifiedas right car fromthe ventral margin of the acetabulum (Fig. 16F). The pal bones and have been exposed in oblique distal view. The cranial border of the acetabulum is thickened and differs one on the right side of Fig. 15 is possibly the triquetrum from that in Kryptobaatar in having a more prominent, (ulnar carpal bone). It is transversely elongated, about 1.75 nodule-like thickening, with an oval pit for ill. rectus femoris mm wide, and has a slightly convex proximal facet fo r in frontof it (arrow in Fig. 16F). The acetabulum is 3.4 mm articulation with the ulna and a smallmedioproximal facet long, 3.2 mm high (both inner dimensions ) and 4.6 mm long for articulation with the lunatum. On the medio distal side (including margins). there is a strongly concave facet for articulation with the The obturator fo ramen has the same proportions relative hamatum (fourth carpal bone). On this facet two nutrient to the length of the pelvis as in Kryptobaatar, being 3.9 mm fo ramina are clearly seen. The bone preserved on the leftside long. Its ventral margin (preserved on the right side) has a in the same piece of rock apparently belongs to the distal row rather unusual shape for mammals, with a small rounded ofthe carpals. The shape indicates that it might be a displaced process that protrudes into the fo ramen (Fig. 16F). Although pisiform (os pisiforme); it is toa large to be the hamatum, as the caudal part of the ventral margin of the fo ramen to the it does not fitthe facet on the triquetrum fo r articulation with rear of the process is slightly distorted, the well-preserved the hamatum. It might also be the trapezoideum (second pro cess does not seem to be an artefact. The caudal border of ca�al bone) or praepollex. In Fig. 15 it is arranged obliquely. It IS strongly elongate and measures about 1.9 mm across its longer diameter. It has a convex proximal facet (facing up Fig. 16. Nemegtbaatar gobiensis (ZPAL MgM-I/8l), isolated parts of skel ward and to the leftin Fig. 15) and a concave distal facet. eton III Fig. 8A. OA, B, C. Proximal part ofright femur in ventrai, dorsal and medial views. OD, E. Anterior part of right ilium in dorsal and medial views. OF. Posterior part of right pelvis, lateral view. OG, H. Incomplete Pelvis and hind limb sacral vertebrae S2-S4 in dorsal and leftlateral views. (For Sl see Fig. 11).
l = trochanteric fo ssa; 2 = posttrochanteric fo ssa; 3 = lesser trochanter; 4 = Pelvis (Figs. 8A, 16D-F, 37A, 39, 41). - The caudal parts of rugose area on greater trochanter for insertion of gluteal musculature; 5 = both halves of the pelvis are preserved in ZPAL MgM-I/81, subtrochanteric tubercle; 6 = postobturator notch (or fo ramen); 7 = displaced vent rally relative to the lumbar vertebrae; the ante indentation on margin of pub is, possibly for epipubic bone; 8 = acetabu rior part of the right ilium (Fig. 16D, E) is preserved sepa lum; 9 � obturator foramen; 10 = S2; Il = S4; leftarrows in D and right �rrows in E=onglll of dorsal part of m. gluteus medius; leftupper arrows rately in frontof the lumbar vertebrae. The estimated length III E = onglll of m. longissimus dorsi; left lower arrows in E = auricular of the pelvis is about 34 mm. The wing of the ilium is similar �urface (two parts), forming medial wall of caudal ventrai iliac spine; arrow to that in Kryptobaatarbut differsin having a more rounded III F = pit for m. rectus femoris. All x4; all except D and E stereo-pairs. FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 27 28 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994) the acetabulum is raised in a similar way as the cranial, with dorsal one. The lesser trochanter is very prominent, similarly a prominent nodule-like structure and a ventrocaudal pit built as in Kryptobaatar. behind it. The dorsal margin of the ischium is thickened The femoral head is more sharply delimited from the (broken on the right side and showing only the medial wall neck than in Kryptobaatar. The heart-shaped rugosity on caudally) and directed dorsally fo rming a concave surface. the head, representing the fovea capitis femoris, which was The ischial tuber is not preserved. The ventral margins of the noted by Jenkins & Krause 1983 as characteristic for multi ischia, fusedin other genera to fo rm a keel, are broken off, tuberculates studied by them, is hardly recognizable. A faint and left and right halves of the pelvis are slightly displaced ridge extends along the distal part of the neck, between the with regard to each other; the keel has not been preserved. head and the base of the greater trochanter. The trochant Caudal to the obturator fo ramen there is a postobturator eric fo ssa is relatively shallow; it extends as a narrow groove notch (possibly a foramen), preserved as a deep indentation onto the distal part of the greater trochanter and narrows on the ventral margin. This is relatively larger and higher proximally (number 1 in Fig. 16A). The post-trochanteric than in Kryptobaatar, and we cannot determine whether it fo ssa, which is shallow in Kryptobaatar, is very deep here, opened into the pelvic cavity. The lateral surface of the and the gluteal crest is much more prominent, fo rming a ischium is concave, especially in the area dorsal and cranio keel that is 2.3 mm wide proximally. In dorsal aspect, at the dorsal to the postobturator notch. From the cranioventral divergence of the neck and the greater trochanter, there is a corner of the postobturator notch, two faint blunt ridges prominent subtrochanteric tuberde, similarly developed as extend craniodorsally and reach the obturator fo ramen. The in Kryptobaatar. area of the apparent fusion of the ischium and pubis is At the distal extremity (Fig. 17B-E), the lateral condyle elevated, extending fromthe ventral margin of the pelvis to (preserved in ZPAL MgM-I1110) pro trudes less over the the above described process at the ventral margin of the shaft than in Kryptobaatar, and the trochlea is shiftedlater obturator fo ramen. ally, doser to the lateral condyle. In cranial view the medial The pubis is relatively small, with an undulating lateral ridge of the trochlea is more prominent than the lateral one. surface. There is a tuberde on the ventrai margin in frontof ? Parafibul a. - A bone fragmentthat may represent a neck of the presumed line of fusionwith the ischium. In frontof the the parafibula,has been preserved in the knee joint in ZPAL tuberde, at a point midway along the length of the pub is, MgM-I1110 (Fig. 17F, H, I). there is a deep, rounded indentation 1.8 mm long and 0.4 mm high, possibly fo r articulation with the epipubic bone. Tibia (Figs. 17F-H, 43). - In ZPAL MgM-I11 1O the lefttibia This is very differentfrom the shallow, elongated indentation is 19.4 mm long, and its proximal extremityis 5.5 mm wide in Kryptobaatar. Dorsal to the indentation there is another in cranial view. This tibia is possibly slightly deform ed, being one, very small and shallow, which may be due to distortion. compressed distally, and as a consequence more strongly The pelvis of Nemegtbaatar appears to be relatively more bent laterally than it originally was. The proximal end is widely open than in Kryptobaatar;the pubes and ischia meet asymmetrical, more triangular than oval, with a rounded, their counterparts possibly at wider angles. Because of the caudally situated spine. In this respect it differsfrom Krypto distortion caused by crushing, these angles cannot be esti baatar and ?Stygimys (Krause & Jenkins 1983, Fig. 23E), in mated. which taxa the proximal end of the tibia is roughly oval and the caudal prominence is small. In Nemegtbaatarthe cauda! Femur (Figs. 8A, 16A-C, 17B-E, 41C, 42). - The femur in border encirdes a large semicircular prominence that abuts Nemegtbaatar differs from thatin Kryptobaatar in having a against the fibula. Laterally the proximal articular surface greater trochanter that is relatively more robust and more bears a prominent hook-like pro cess (Fig. 17F, H, I). The strongly protruding proximally over the head (Fig. 16A-C). proximal articular surfaces are more prominent than in There is a ridge that delimits the triangular rugose area for Kryptobaatar, inasmuch as the concavities of the medial and insertion of the gluteal musculature (on the caudal part of the lateral articular facets are deeper in Nemegtbaatar. The tibial ridge). On the cranial part of this ridge originated the apo neurosis for m. vastus lateralis. This ridge is better developed in Nemegtbaatar than in Kryptobaatarin that it is higher, exhibits fine crenulations and has a pitted furrow along its Fig. 17. DA. Chulsanbaatar vulgaris (ZPAL MgM-I/99b), Red beds of distal and medial sides. In lateral view the rugose area fo r Khermeen Tsav, Khermeen Tsav Il, Gobi Desert, Mongolia. Partial left knee joint; fem ur to the right. Lateral view. DB-I. Nemegtbaatar gobiensis attachment of gluteals is longitudinally divided by a faint (ZPAL MgM-I/IIO), horizon and localityas in A. DB-E. Distal part ofleft furrow,at the ventral side ofwhich inserts m. gluteus medius fe mur. DB. Dorsal (slightly lateral) view. DC Lateral view. OD. Medial (Fig. 42C). In proximalview this area is divided by a furrow view. DE. VentraI view. OF-I. Lefttibia and fibulain lateral, media!, caudal directed fromthe ventromedial to the dorsolateral side into and cranial views. l = tibia; 2 = fibula,3 = hook-like lateral process offibula; 4 = media! condyle; 5 = lateral condyle; 6 = hook-like lateral process oftibia; two semicircular parts, the lateral of which is larger. The 7 = fragmentof a ?parafibula;8 = tibial tuberosity; 9 = cranial crest; arrow medial part is subdivided by a shallow, dorsally concave in G = pit for lig. collaterale mediale; arrow in I = fusiform area forinsertion furrowinto a larger, oval, ventral part and a crescent-shaped of m. semimembranosus anterior. All x4; stereo-pairs. FOSSILS ANDSTRATA 36 (1994) Anatomy and habits of multituberculates 29 30 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS ANDSTRATA 36 (1994) tuberosity is distinct but flattened. The cranial (anterior) not preserved. The head is 2.2 mm long craniocaudally and crest (number 9 in Fig. 171) is sharp proximally. At the 4.1 mm wide (including the hook-like process) in caudal middle of the length, the shaft is 2.5 mm wide transversely view (Fig. 17H). The facet for articulation with the parafibula and 1.3 mm craniocaudally. The tibia in ZPAL MgM -Il IlO is is very large. Alongthe caudal wall of the shaftthe re extends 19.4 mm long (compared with 18.8 mm in Kryptobaatar, a sharp crest, not exposed in Kryptobaatar. ZPAL MgM-I14l), but otherwise it is much more robust than in Kryptobaatar. Extending along the proximal part of the medial wall, cranial and parallel to the cranial crest, is a Genus Kielan fusif orm area fo r insertion of m. semimembranosus anterior Chulsanbaatar (arrow in Fig. 171 and Fig. 43C, D). These structures are not Jaworowska, 1974 Kryptobaatar. recognizable in Kielan The distal end comprises the epiphysis, distinctly sepa Chulsanbaatar vulgaris rated from the shaft, whichindicates the young age of the Jaworowska, 1974 individual (Fig. 17F-I). The distal lateral condyle and (Figs. 17A, 18-25, 37B) medial malleolus are poorly recognizable, but apparently Material. - We tentatively assign to Chulsanbaatar vulgaris they were less prominent than in ? Eucosmodon (Krause & all small postcranial multituberculate fragmentsfo und in the Jenkins 1983, Fig. 22A, B). In ?Eucosmodon we recognize Barun Goyot Formation and in the Red beds of Khermeen on the distal surface of the tibia two condyles (lateral and Tsav. It cannot be excluded, however, that some of these small medial) and the medial malleolus (Fig. S6E, F), but skeletons, especially those not associated with skulls, belong in Nemegtbaatar the medial condyle apparently was not to another, as yet unrecognized, multituberculate taxon. developed, as is characteristic also of an unidentified tibia Barun Goyot Formation: ZPAL MgM-I/61, Khulsan: skull from the Hell Creek Formation (Fig. SSA; see also 'Ana with dentaries, damaged C2-T2, cervical ribs preserved on tomical comparisons'). C2 and on CS, an isolated cervical rib possibly of C7, a Fibula (Figs. 17F-I, 43A). - The length ofthe fibulain ZP AL damaged fragment of the scapulocoracoid in articulation MgM-I1110 cannot be given because the distal epiphysis with damaged proximal fragment of the right humerus. (including the distal caudal tuberosity; see Kryptobaatar) is ZPAL MgM -Il III, Nemegt, Eastern Sayr: skull with den-
Fig. 18. DA, B. Chulsanbaatar vulgaris (ZPAL MgM-1/ 83), Red beds of Khermeen Tsav, Khermeen Tsav Il, Gobi Desert, Mongolia. Flattened skull, dentaries and fairly complete, damaged postcranial skeleton without caudal vertebrae and distal parts of the limbs, as pre served, after some preparation. DA. Leftlateral view.
DB. Right lateral view. I = left humerus; 2 = L7; 3 =
incomplete sacrum; 4 = left femur; 5 = left tibia (in
complete fibulaparalleI to it); 6 = right femur; 7 = right
i1ium; 8 = right humerus; 9 = right scapulocoracoid; 10
= proximal part ofright radius and ulna. See also Figs. 22 and 23. Some elements figured in Fig. 22 are not exposed. Both xl; stereo-pairs. FOSSILS ANDSTRATA 36 (1994) Anatomy and habits of multituberculates 31 taries, atlas, C2-C4, the body of Cs, ventral parts of both incomplete pubes and ischia in articulation with a partial left scapulocoracoids in articulation with proximal parts ofhu and a complete right femur, the latter in articulation with the meri, distal part of the right radius in articulation with the right tibia and fibula, patelIa and the parafibula; this speci scaphoideum. ZPAL MgM-I1138, Khulsan: skull with den men may not belong to Ch. vulgaris. Specimen 99b consists taries associated with broken fragmentsof the long bones. of an incomplete right femur in articulation with the tibia ZPAL MgM -1/140, Khulsan: skull with dentaries, associated and fibula,the shaftof the leftfe mur and incomplete leftpes with broken fragmentsof ribs and long bones. ZPAL MgM- that includes the tarsus and five metatarsals. ZPAL MgM-I/ 1/143, Khulsan: anterior part of the skull, dentaries, poorly 108: skull, dentaries, five cervicals, exposedin ventral view, preserved fragments of cervicals and long bones; ZPAL partial leftscapulocoracoid in articulation with the proximal MgM-I/149, Khulsan: left dentary associated with incom part of the humerus, partial leftfe mur, broken ribs. ZPAL plete leftpelvis. ZPAL MgM-I1 1s1, Khulsan: isolated upper MgM-I114s: skull with a fragmentof the leftdorsal arch of teeth and fragments of edentulous dentaries, radius, frag the adas, both dentaries, the proximal part of a damaged left ments of metatarsals, incomplete ilia and ischia with partial humerus, a partial hyoid arch and some unidentified bones femora in acetabula; this specimen may not belong to Ch. below it. vulgaris. ZPAL MgM -I1170a, Nemegt: postcranial fragments only: L6, L7, partial sacrum, parts ofboth ilia, proximal part Skull of the right femur. Figs. 18, 19B and 20C Red beds of Khermeen Tsav, Khermeen Tsav Il: ZPAL MgM -I183: skull, dentaries, bodies of C2-T2, bodies of?T7- Numerous skulls of Chulsanbaatar were described by T13, U-L7, incomplete sacrum, numerous broken ribs, Kielan-Jaworowska (1974), Kielan-Jaworowska etal. (1986), fragmentary right and left scapulocoracoids, right and left and Hurum (1992, 1994). In the present paperwe figureonly humeri, each in two parts, proximal parts of right and left three skulls found in association with postcranial fragments. radii and ulnae, right ilium, left ischium, right and left femora, left tibia and fibula (without the proximal part). Hyoid apparatus ZPAL MgM -I184: skull cut on the microtome (Kielan-Jawo Fig. 19 rowska et al. 1986; Hurum 1992, 1994), fragments of the In ZPAL MgM-I/14s an incomplete hyoid apparatus has cervical vertebrae and humerus, fragmentsoflong bones; all been preserved below and somewhat caudal to the skull (Fig. the postcranial elements are badly damaged. ZPAL MgM -Il 19). The preserved part consists oftwo stylohyoid bones that 85 only postcranial skeleton: damaged sacrum, partial ilia form an angle of 80°, almost touching each other. The and ischia, proximal part of the leftfe mur, the femoral head basihyoid and the rest of the hyoid apparatus have not been and greater trochanter ofthe right femur; both femoral heads preserved. Both stylohyoid bones have been pushed caudally are in acetabula. ZPAL MgM-I/99a and ZPAL MgM-I/99b and turned a litde more than 90° ventrocaudally, so that in fo und together in the same piece of rock: 99a is a very young Fig. 19B their point of juncture is directed caudally. When individual; the skeleton consists of two dentaries, fused,
Fig. 19. Chulsanbaatar vulgaris (ZPAL MgM-II145), Red beds of Khermeen Tsav, Khermeen Tsav Il, Gobi Desert, Mongolia. DA. Partial hyoid apparatus separated fromskuJl in B, dorsal view. DB. AImost complete skull with both dentaries, showingpartial hyoid apparatus, rotated ventrocaudallyfromits natural position. l = leftstylohyoid bone; 2 = right stylohyoid bone. Stylohyoid bones appear smaller in B than in A because of oblique position ofhyoid apparatus in B. Both X4; A stereo-pair. 32 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994) the piece of rock containing the stylohyoidbones was sepa relatively large and flat, roundedcaudally and directed ob rated fromthe skult, the photograph in Fig. 19A was taken, liquely caudally, more ventrally than horizontally. Although showing the hyoids in dorsal aspect. Both hyoids are cracked. the suture with the transverse process is hardly discernible, The right one, which is more complete and better preserved, we identifythis structure tentatively as a cervical rib, as it is is 5.8 mm long (the length of the skull is 18.6 mm). The similar in position and shape to that of Ornithorhynchus stylohyoids are convex dorsally, slightly sigmoidal and (Lessertisseur & Saban 196?a). slightly expanded at both ends. C3-C7. - These vertebrae are preserved in severai specimens (see 'Material') and are badly damaged. The laminae, partly Axial skeleton preserved in ZP AL MgM -1/61 (Fig. 20B) and ZPAL MgM-1/ Figs. 18, 20, 21 III are directed dorsomedially, but possibly less dorsally than in Nemegtbaatar. Otherwise they do not reveal features CERVICAL VERTEBRAE AND CERVICAL RIBS that would differentiate them fromthose ofNemegtb aatar. A Atlas. - In ZPAL MgM- Il III (Fig. 20C) the atlas is complete, badly damaged apparent right cervical rib, associated with preserved between the skull and the axis, its ventral arch C5 (Fig. 20B), is preserved. In lateral view this element is flat, being obscured by the axis and the foUowing cervicals. As the roughly oval, narrowing caudally, directed horizontally and bones are strongly cemented and cracked, the atlas was not slightly ventrally. Posterior to the fifth cervical rib, another removed fromits original position. In caudal view the atlas is apparent cervical rib has been preserved, possibly the 6.6 mm wide (including the transverse processes), and its seventh, obscured in Fig. 20B. This one differsfrom the fifth height in lateral view is 3.3 mm. The right andleftlaminae are one in having a less curved outline. separated at the top. The transverse process, weU preserved on the leftside, is relatively small, roughly rectangular, trans THORACIC VERTEBRAE AND RlBS versely elongated and with rounded tips. The transverse The anterior thoracic vertebrae preserved in two specimens fo ramen is absent. The leftfragment of the atlas preserved in (ZPAL MgM-1/61 and ZPAL MgM-1/83) are badlydamaged ZPAL MgM-1/145 has a transverse process and a caudal and are therefore not described. The seven posterior tho articular surface that is almost flat. racics preserved cranial to U-L? in ZPAL MgM-1/83 (Fig. Axis. - The arch is incomplete in all three specimens (see 18) are also damaged. Only the bodies are preserved, but they 'Material'), and the size of the spinous process is not known. are obscured by broken ribs in several places. The number of In ZPAL MgM-1/61 (Fig. 20A), on the displaced axis the left thoracic vertebrae is not known in multituberculates. We cervical rib is preserved in articulation with the axis. It is tentatively assume that there were 12 thoracics in Chulsan baatar, and we designate the seven posterior thoracics as T6-
Fig. 20. Chulsanbaatar vulgaris. DA, B. ZPAL MgM-I/61, Barun Goyot Formation, Khulsan, Gobi Desert, Mongolia. DA. Damaged axis in cranial view. DB. C2-Tl of same specimen (C2 is displaced and poorly seen) in leftlateral view. Apparent seventh cervical rib has been displaced and is not seen in this view.
De. ZPAL MgM -1/ Ill, horizon and locality as in A. Skull and anterior cervical vertebrae in caudal view. l = apparent leftcervical rib of the axis; 2 = fifth cervical rib; 3 = atlas, showing transverse processes; 4 = damaged C2-C3. A, B x8; C X4; A, C stereo-pairs. FOSSlLS ANDSTRATA 36 (1994) Anatomy and habits of multituberculates 33
Fig. 21. Chulsanbaatar vulgaris. DA, B. ZPAL MgM-II170a, Barun Goyot Formation, Nemegt, Gobi Desert, Mongolia. L6, L7, partial sacrum, partial ilium, and proximal part of right femur. DA. Leftlateral view. DB. Ventrai view. De, D. ZPAL MgM-I/85. Red beds of Khermeen Tsav, Khermeen Tsav Il, Gobi Desert, Mongolia. Damaged sacrum, ilia, and ischia, proximal part ofleftfe mur, femoral head and greater trochanter of right femur; both femoral heads are
in acetabula. DC Right lateral view (dorsal is to the left).DD. Dorsal view. l = L7; 2 = Sl; 3 = 52; 4 = ilium; 5 = femoral head in acetabulum; 6 = broken right
femur; 7 = lesser trochanter; 8 = subtrochanteric tubercle; upper arrow in B = crest on transverse proeess of Sl; lower arrow in B = facet on right ilium for articulation with the transverse process of 52. All x4; stereo-pairs. 34 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
Fig. 22. Chulsanbaatarvulgaris. DA-D. ZPAL MgM-Il Ill, postcranial elements associated with skull in Fig. 20e. DA. Distal end of right radius, in articulation with damaged scaphoideum, ventral view. DB-D. Same individual, proximal end of lefthumerus in articulation with ventral end of scapulocoracoid. DB. Proximal view ofhumerus, ventrai view of scapulocoracoid. De. Humerus and acromion in ventrai view. OD. Scapulocoracoid in cranial view, humerus in dorsal view. DE, F. ZPAL MgM-I183. DE. Lateral view ofulna and radius of individual in Fig. 18, in articulation with distal end of poorly preserved humerus.
OF. Same specimen, proximal view ofulna and dorsal view ofhumerus. l = radius; 2 = scaphoideum; 3 = acromion; 4 = coracoid process; 5 = greater tubercle;
6 = origin of m. infraspinatus; 7 = intertubercular groove; 8 = ulna; 9 = distal end of humerus. All x8; stereo-pairs.
Il2. The lengths oftheir bodies are: T6 1.7 mm, T7 1.8 mm, 1.9 mm long. The spinous processes on Ll-L3 (in ZPAL T8 1.8 mm, T9 2.0 mm, IlO 2.1 mm, Il12.1 mm and Il2 2.3 MgM-l/83) are directed mostly cranially, only slightly dor mm. Poorly preserved costal foveae are preserved on some of sally, and are possibly rounded at the extremities and overlap the bodies, but the caudal costal foveae are uncertain on Il2. each other. Those on the successive vertebrae rise more Fragments often ribs have been preserved on the leftside steeply dorsally. The pre- and postzygapophyses are rela ofZPAL MgM-l/83 (Fig. 18),in association with the thoracic tively large. In ventral aspect all the lumbars have a promi vertebrae. They are too poorly preserved to be described. nent crest. On Ll, at the place of the cranial costal fovea, on the right side, below the poorly preserved postzygapophysis, LUMBAR VERTEBRAE a small rounded piece of bone is preserved that might be the The lengths ofthebodies in ZPALMgM-l/83 (Fig. 18) are: Ll broken-offhead of the last rib. If so, the vertebra recognized 2.4 mm, L5 2.4 mm, L62.7 mm and L7 1.9 mm (other bodies by us as Ll is indeed the firstlumbar, which indicates that are distorted). In ZPAL MgM-II170a, L6 is 2.7 mm and L7 there are seven lumbars in Chulsanbaatar. F055IL5 AND 5TRATA 36 (1994) Anatomy and habits of multituberculates 35
Fig. 23. Chulsanbaatar vulgaris (ZPAL MgM-I/ 83). A-D. Proximal end of left humerus of individual in Fig. 18. DA. Lateral view. DB. Dorsal view. DC Proximal view. OD. Medial view. DE. VentraI view. l = greater tubercle; 2 = lesser tubercle; 3 = deltopectoral crest; 4 = posterior crest; 5 = teres tuberosity; 6 = intertu bercular groove. All x8; stereo-pairs.
5ACRUM than it was originally. In dorsal view the fusedarches form a Figs. 18, 21 flat triangular area that tapers caudally. The prezygapo The sacrum is very long and narrow. The estimated length physes are preserved only in ZPAL MgM -Il 170a, exposedin (measured in ventral aspect) of ZPAL MgM-II1 70a (Fig. ventral aspect (Fig. 2lB). The transverse processes of51 are 2lA, B) is 9-10 mm, and the maximum width (measured partly preserved in ZPAL MgM -111 70a (exposed in ventral across the lateral margins of the transverse processes of the aspect) and are fused with the ilia. On both sides their firstvertebra fusedto the ilia) is 6.2 mm. The lengths of the anterior parts are broken, and it seems that the auricular two firstsacral vertebrae in this specimen are 5 l 2.0 mm and surface was much larger (extended furthercranially) than it 52 2.7 mm. In ZPAL MgM-I/85 (Fig. 21e, D) the sacrum has been preserved. A crest extendslaterocau dally across the exposed in dorsal view is badly damaged, and its dimensions transverse pro cess (upper arrow in Fig. 21B). The transverse cannot be given. In ZPAL MgM-I/83 (Fig. 18), 51 is 1.9 mm processes of52 are broken, but the facet for articulation with long and 52 2.2 mm. In ZPAL MgM-I/83 the sacrum is the right process is recognizable on the right ilium (lower compressed dorsoventrally and appears flatter than it was arrow in Fig. 2lB). We conclude that 51 and 52 articulated originally. The dorsal sacral fo ramina are, in dorsal view, with the ilium as in Kryptobaatar. obscured by the flattenedarea of the fusedlaminae. The first In ventral view in ZPAL MgM-I/83 and ZPAL MgM-II and second leftdorsal fo ramina are preserved and seen in left 170a, the body of the firstvertebra is insignificantlyshorter lateral view. Because of deformation, the pedicles appear than that of L7 (contrary to the condition in dorsal view). very low, and the intermediate sacral crest is more prominent The transversely aligned areas of separation of the vertebrae 36 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994) are developed as transverse, blunt ridges. No ventral sacral D). The length of the humerus cannot be determined. The fo ramina are preserved. There is a distinct median ventral proximal part of the Chulsanbaatar humerus appears rela crest on all the vertebrae, lateral to which the surfaces of the tively gracile; it is most similar in proportions to that of body are concave. On the preserved fragmentof S4 in ZPAL Tugrigbaatar (Kielan-Jaworowska & Dashzeveg 1978), al MgM -Il 17Da, the median crest is less prominent than on the though in this latter genus it was possibly reconstructed toa preceding vertebrae. long (see 'Anatomical comparisons'). The similarity con cerns the shape of the head that strongly overhangs the shaft, the position and relative sizes of the greater and lesser Pectoral girdle and forelimb tubercles, the shape ofthe teres tuberosity and apparently the Figs. 22, 23 shape ofthe intertubercular (bicipital) groove, only the most Scapulocoracoid. - The scapulocoracoids are preserved in proximal part of which has been preserved in Tugrigbaatar. three specimens (see ' Materiaf). They are incomplete, rep re This gro ove in Chulsanbaatar narrows distally and then sented by ventral ends. The glenoid fossa is complete on the widens again as in Nemegtbaatar, but is less deep than in left side of ZPAL MgM-II1ll (Fig. 22B-D). The suture Nemegtbaatar. Only a small part of the distal end of the left between the coracoidal and scapular parts of the glenoid humerus preserved in ZPAL MgM-I/83 (Fig. 18, 22E, F) can fo ssa is not discemible. The coracoid is expanded medially be seen, and therefore it cannot be described in detail. and laterally. As its medial margin is broken off, it is possible that the coracoid was more expanded medially than laterally, Radius and ulna. - The proximal part of the left ulna and being roughly L-shaped. The acromion, preserved in ZPAL radius have been preserved in articulation with the humerus MgM-II83 and ZPAL MgM-I/lll (Fig. 22B-D) is roughly inZPAL MgM-I/83 (Figs. 18,22E, F) and the distal end ofthe peg-shaped as in Nemegtbaatar. In ZPAL MgM-I/ll1 the right radius in ZPAL MgM-IIll1 (Fig. 22A). The olecranon glenoid fo ssa and the acromion embrace the humerai head, preserved in ZPAL MgM-II83 is relatively large. Otherwise, which is preserved in articulation with the scapulocoracoid. both specimens are very poorly preserved and do not merit description. Humerus (Figs. 18, 22, 23). - In ZPAL MgM-II83 (Figs. 18, 23) the proximal parts of both humeri and a poorly pre served distal part of the lefthumerus in articulation with the Pelvie girdle and hind limb fragments of an ulna and radius are preserved. In ZPAL Pe/vis (Figs. 18B, 21, 24, 37B). - The incomplete pelves are MgM- Il III the proximal parts of both humeri in articula preserved in five specimens (see 'Materiaf). The pelvis of tion with scapulocoracoids have been preserved (Fig. 22B- Chulsanbaataris more similar to that of Kryptobaatarthanto
Fig. 24. DA-C. ?Chulsanbaatar vulgaris (ZPAL MgM-I/99a), Red beds of Khermeen Tsav, Khermeen Tsav Il, Gobi Desert, Mongolia. Partial pubes and ischia in articulation with proximal part of leftfe mur and nearly complete right fe mur in articulation with partial tibia, proximal (broken) part of fibula, patelIa and broken parafibula. DA. Pelvis in oblique lateroventral view; cranial margin up. DB. Same specimen, showing pelvis in dorsal view and fe mora arranged somewhat obliquely with respect to plane of photograph. DC. Same specimen with femora arranged in plane of photograph. l = ventraI keel; 2 = broken proximal part of fibula; 3 = patelIa; 4 = parafibula; 5 = subtrochanteric tubercle; 6 = obturator fo ramen; 7 = ischium; 8 = pub is; 9 = tibia. All x4; A, B stereo-pairs. FOSSILS ANDSTRATA 36 (1994) Anatomy and habits of multituberculates 37
Fig. 25. DA-D. Chulsanbaatar vulgaris (ZPAL MgM-I/99b), calcaneum Red beds of Khermeen Tsav, Khermeen Tsav Il, Gobi Desert, Mongolia. Camera lucida drawings ofleftpes fo und in association with skeleton in Fig. 17 A. Roman numerals denote the metatarsals. DA. Medial view. DB. Dorsal view. DC Dorsolateral view. OD. Lateral view. Scale bar 5 mm.
III
III O III
that of Nemegtbaatar. The estimated length of the pelvis in The ventrai margin is fused with its counterpart to form a ZPAL MgM -I/83, based on a comparison with Kryptobaatar, keel, the depth ofwhich is 0.8 mm in ZPAL MgM -I199a (Fig. is 20.7 mm. The ilium is very slender and elongate, 13.8 mm 24A). The postobturator foramen is not preserved, but it long in frontof the acetabulum. The caudal ventral iliac spine appears that in ZPAL MgM -I/8S the missing part ofthe bone is similar in shape to that in Kryptobaatar. It differsfrom that (the enlarged opening is confluentwith a partly damaged in Kryptobaatar in having the anterior extremities more obturator foramen) may have housed the postobturator strongly reflectedlaterally. The height of the ilium is 1.2 mm fo ramen or notch. The pubes are not completely preserved, caudal to the ventral iliac spine and 2.1 mm along it. It was but it may be concluded from the preserved parts that, difficultto measure the length of the auricular surface, but it similar to the ischia, theywere fusedventraUy to fo rm a keel. appears fromthe preserved parts that it was relatively shorter Femur(Figs. 18, 21, 24). - The right femur in ZPAL MgM-I/ than in Kryptobaatar, the sacrum being less firrnly synos 83 (Fig. 18) is 18.5 mm long; in ZPAL MgM-I/99b it is still tosed to the pelvis. The cranial margin of the acetabulum is larger and more robust, while in ZPAL MgM -I/99a (juvenile thickened and has a cranioventral pit. However, the promi individual, Fig. 24) it is 9.8 mm long. In this latter specimen nent nodule-like thickening characteristic of Nemegtbaatar the boundaries between the shaft and theepiphyses are more is absent. The body ofthe ilium, cranioventral to the acetabu distinct than in other specimens, and the femoral head fo rms lum, is relatively smaller than in Nemegtbaatar, and there is the proximal epiphysis of the femur. The femur in Chulsan no ridge dividing it into two parts. The caudal margin of the baataris slender, more similar to that ofKry ptobaatarthan to acetabulum is raised possibly higher than in Kryptobaatar, that ofNe megtbaatar. There is some variation among studied and there is a deep pit immediately below it, which, contrary femora, fo r example, in the relative size of the greater tro to the condition in Kryptobaatar and Nemegtbaatar, lies chanter. In the smallest specimen, ZPAL MgM-I/99a (Fig. within the acetabulum. The length of the acetabulum is 2.3 24), and a somewhat larger one, ZPAL MgM-I/1S1 (both of mm in ZPAL MgM-I/8S (Fig. 21C, D) and 1.9 mm in ZPAL which may not belong to Ch. vulgaris), the greater trochanter MgM-I1170a (Fig. 21A, B). ZPAL MgM-I/99a (Fig. 24) rep hardly protrudes over the femoral head proximally, while it resents a juvenile individual, inasmuch as the sutures be is more prominent in larger specimens. However, even in tween the bones ofthe pelvis are not synostosed. The ilium in these latter specimens it is relatively smaller than in Krypto this specimen is missing, but the preserved parts ofthe pubes baatarand much smaller than in Nemegtbaatar. The gluteal and ischia clearly show the places of fusion withthe ilium, as crest is less prominent than in Nemegtbaatar. The lesser weU as a relatively large contribution of the pubis to the trochanter appears more prominent, more strongly pro acetabulum. The obturator foramen is placed ventrocau truding ventrally in Chulsanbaatarthan in Kryptobaatar and dally to it, but possibly relatively more caudally than in other Nemegtbaatar. The trochlea is more asymmetrically placed genera. The obturator fo ramen may be measured onIy in than in Kryptobaatar. ZPAL MgM-I/99a (Fig. 24), where it is l.S mm long and 1.3 mm high. The dorsal margin of the ischium is typically a PatelIa. - The pateUa has been preserved on the left side of concave arch that is oriented dorsocaudally. The ischial tuber ZPAL MgM-I/99a (Fig. 24B, C). It sits within the knee joint is not preserved. The lateral side of the ischium is concave. below the femur, displaced laterally, arranged transversely 38 Zofia Kielan-Jaworowska & Petr P. Gambaryan F055IL5 AND 5TRATA 36 (1994) with its convex surface oriented craniodorsally. It is 1.7 mm the proximal end of Mt V apparently articulated with the wide, and in comparison with the width of the distal epiphy distal margin of the calcaneum medial to the peroneal sis of the femur, which is 2.2 mm, it appears relatively wider groove. The peroneal groove is wide, as in Kryptobaatar, than in small extant eutherian mammals. and the peroneal tubercle is directed laterodistally. The dor sal surface of the astragalus (poorly preserved) appears rela Tibia (Figs. 17A, 18, 24). - The left tibiain ZPAL MgM-I/83 tively flat. The mediodistal rounded process with a saddle is 13 mm long. A part of the proximal end is missing, the shaped sulcus fo r articulation withthe navicular is exposed, distal end is complete, and no suture between the epiphysis and it appears to be similar to that in Kryptobaatar. The and the shaft is seen. The proximal part of the right tibia is joint between the entocuneiform and Mt I appears similarly preserved in a juvenile ZPAL MgM -I199a. In ZPAL MgM -Il shaped to that in Kryptobaatar (Fig. 7E-G). All other tarsal 99b (Fig. 17 A) the right tibia is nearly complete, only the and metatarsal bones do not differin shape and proportions distal end is missing; the preserved part is 13 mm long, fromthose in Kryptobaatarbut, because of the poor state of whereas the whole tibia was probably about 14 mm long. The preservation of the bone surface, the details of their struc proximal articular surface is incomplete. All of these tibiae ture cannot be given. are incomplete and do not show the details that would allow comparisons with Kryptobaatar. Fibula (Figs. 17A, 18, 24B, C).- In ZPAL MgM-I183 (Fig. 18) Family Sloanbaataridae Kielan the right fibulais preserved without the proximal end. The Jaworowska, 1974 distal part preserves the caudal tuberosity. The distal fibular end is situated caudallyto the tibia. In ZPAL MgM -I199a the Genus Kielan-Jaworowska, proximal part of the left fibula is preserved. The head is Sloanbaatar relatively stout, and the characteristic hook-like process is 1970 preserved. In ZP AL MgM -I/99b (Fig. 17A) a nearly complete Kielan fibula,lacking only the distal extremity, is preserved in asso Sloanbaatar mirabilis ciation with the tibia and femur. In allof these specimens, the Jaworowska, 1970 fibulaeare relatively more slender than in Kryptobaatarand (Figs. 26, 37C) Nemegtbaatar. In ZPAL MgM -I199b the estimated length of Material. - Bayn Dzak, Ruins, Djadokhta Formation, ZPAL the fibulais about 13.6 mm, and its width at the longitudinal MgM-I/20: skull, dentaries and badly damaged postcranial midline is, in lateral view, 0.42 mm, which is 0.031 of its fragments consisting of incomplete ischia, anterior part of length, while in Kryptobaatarthe width of the fibulais 0.059 the leftilium, right femur, L5-L7 in articulation with dam of its length. aged 51 and somewhat separated fromthese in the matrix, Parafibula. - The parafibulahas been preserved only on the and 54 in articulation with Cd1 and Cd2. left side ofZPAL MgM-I/99a (Fig. 24B, C). It is a tiny, slightly cracked ossicle, similar in shape to that in Kryptobaatar, Axial skeleton slightly displaced, directed dorsally, adhering with its neck to the proximal end of the fibula. Lumbar vertebrae. - Two lumbar vertebrae are poorly pre served and do not reveal any important details. Tarsus and pes. - A lefttarsus with fiveincomplete metatar Sacrum. - The bones are preserved in two parts, and the sals has been preserved in ZPAL MgM-I199b (Fig. 25). The estimated length of the sacrum is about 10.5 mm; the length hind-limb bones in this skeleton are incomplete, and their of the last sacral vertebra is about 3.5 mm. measurements are only tentative. The length of Mt HI is about 3.2 mm, which is 0.24 of the estimated length of the tibia, while in Kryptobaatarthe length of Mt HI is 0.39 the Pelvie girdle and hind limb length of the tibia (13.2 mm). It is thus probable that the Pelvis (Figs. 26, 37C). - The preserved parts of the ilia are metatarsals were relatively shorter in Chulsanbaatar than in heavily damaged and do not differfrom Krypt obaatar. The Kryptobaatar. Because of the smallsize of the specimen and fragmentaryischia are strongly fusedventrally to form a keel, its poor state of preservation, we were unable to obtain good which is about 1.3 mm deep. The caudal part of the right photographs. The distal bones of the tarsus have been pre ischium below the broken ischial tuber has a well preserved served in articulation with the metatarsals. The tuber calca surface, on which we base our reconstructions of the muscu nei has been shiftedin a plantar direction. The most medial lar attachments of this region. part of the distal margin of the calcaneum fitsthe concavity in the cuboid. The medioproximal facet of Mt V articulates Femur. - The proximal part of the right femur is damaged, with the cuboid, while the small facet on the dorsal side of but appears to be generally similar to that of Kryptobaatar. FOSSILS ANDSTRATA 36 (1994) Anatomy and ha bits of multituberculates 39
Fig. 26. DA, B. Sloanbaatar mirabilis (ZPAL MgM -1/20), Djadokhta Formation, BaynDzak, Gobi Desert, Mongolia. Broken posterior part ofpelvis. DA. Ischia, ventrai view. DB. Same specimen in right lateral view. l = ventrai keel; 2--4 denote muscular origins: 2 = m. gemelli; 3 = m. biceps femoris posterior; 4 = m. semiten dinos us. Both x6; A stereo-pair.
Family Taeniolabididae Granger & postzygapophyses are very long, but the exact measure Simpson, 1929 ments cannot be given. In dorsal view a median ridge ex tends longitudinally (not preserved in the anterior one Genus Kielan-Jaworowska, third of the length); at the caudal end it divides into two Catopsbaatar ridges, leaving a triangular concave area in between. Lateral 1994 to the dorsal ridge there extend parallei weak ridges at the edge between the dorsal and lateral sides of the vertebra; Catopsbaatar catopsaloides (Kielan Jaworowska, 1974) (Fig. 27)
Synonymy. - D 1974 Djadochtatherium catopsaloides sp. nov. - Kielan-Jaworowska, p. 40, Fig. 6, PIs. 5:9, 17:2, l 8-2 l. D 1979 Catopsalis catopsaloides (Kielan -J aworowska) Kielan-Jaworowska & Sloan, Figs. l, 2B. Holotype.- See Kielan-Jaworowska (1974). Material. - Red beds of Khermeen Tsav, Khermeen Tsav Il, ZPAL MgM-I/171: badlydamaged broken fragmentsoflong bones, one middle caudal vertebra and three more posterior caudal vertebrae in anatomical position. We refer this speci men to C. catopsaloides, as it has been fo und in beds yielding three skulls of this species. The postcranial fragments are of an appropriate size to be considered conspecificwith the skulls described and figuredby Kielan-Jaworowska (1974).
Caudal vertebrae. - The body ofthe middle caudal vertebra (Fig. 27 A) is 10 mm long, strongly compressed laterally at its longitudinal midpoint, and slightly widening cranially Fig. 27.DCatopsbaatar catopsaloides (ZPAL MgM-l/l71), Red beds of and caudally; the distance between the pre- and postzyga Khermeen Tsav, Khermeen Tsav I, Gobi Desert, Mongolia. DA. Com pophysis is 12 mm. It seems that the strong lateral compres pressed middle caudal vertebra, dorsal view. DB. Three damaged middle sion of the vertebra is in part due to the state of preserva caudal vertebrae, fo und in association with individual in A, more posterior than vertebra in A, lateral view (dorsal to the left).Fragments of the haemal tion. The width of the body is 3.3 mm in cranial view. The arches found in association with vertebrae are not seen in the photograph. spinous and transverse processes are lacking. The pre- and A X4; B x2; stereo-pairs. 40 ZofiaKielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994) these ridges continue caudallyas the lateral margins of the postzygapophyses. On the ventral side of the body there are Myological reconstructions two longitudinal ridges, with a gullybetween them. Poorly preserved foveae for haemal arches are recognizable at the The areas of origin and insertion of particular muscles are posterior end of the body. generally not seen on the photographs published in this Three caudal vertebrae fromthe posterior part of the tail paper. In many cases, however, we were able to identify (Fig. 27B) are strongly laterally compressed, partly because of them, examining the specimens at high magnifications un damage. The pre- and postzygapophyses (partly broken) der Wild-Leitz binocular microscope and changing the were shorter than in the middle caudal vertebra described source ofthe light. N evertheless, the reconstructions of mus above, but otherwise show a similar structure. In the last one culature that follow, as usual in fo ssil material, must be that has been retrieved fromthe matrix afterthe photograph regarded to some extent as tentative. in Fig. 27B was taken, there is a deep longitudinal furrowat the ventral side of the body. A broken fragmentof a relatively long haemal arch has been preserved between the first and Muscles of the forelimb the second vertebra. The skeietal fragmentsof the shoulder girdle and fo relimbs preserved in Late Cretaceous Asian taxa described above are fragmentary.That is why we base our reconstructions of the Taeniolabidoid, fam. gen. et sp. indet. fo relimb muscles also on isolated bones fromthe Late Creta (Kielan-Jaworowska 1989) ceous of North America in the AMNH collection and on the Fig. 28A humeri of? Lambdopsalis bulla (referred to below as ? Lambd opsalis) from the Eocene of China in the IVPP collection. Material. - Djadokhta Formation, BaynDzak, Main Field, Because of the fragmentarynature of this material we are ZPAL MgM -I/165: C2-C7, manubrium of the sternum, one unable to discuss below the origin and insertion ofparticular sternebra, incomplete leftscapulocoracoid, proximal part of muscles ofthe same individual or species, as we do in the case the right humerus and fragments of ribs, described and of the hind limb. As the multituberculate postcranial skel figuredby Kielan-Jaworowska (1989). eton, at least in members of the Cimolodonta, is fairly uni form (Krause & Jenkins 1983) and differs strongly from Axial skeleton those of other known mammals, we assume that the muscu lature was also homogenous in members of this suborder. Cervical vertebrae. - The axis figuredby Kielan-Jaworowska Therefore we reconstruct below some muscles of cimolo (1989, Fig. 1 and Pl. 15 and 16:1) is fused with C3, and two dont multituberculates on the basis of scars preserved on pairs of transverse processes are present on the fused verte bones belonging to different genera from various geological brae. The processes of C2 and C3 are very long. The caudal times and geographical regions. We are fully aware of the part of the right transverse process of C2 is broken off, but danger of such a generalization, but otherwise the recon displaced, and now forms an angle with the anterior part. On struction of the muscles of the anterior part of the body the left side of this vertebra the transverse process is com would not be possible. In some cases actual reconstructions plete, but the suture is not preserved.The sutures cannot be were not feasible, and we describe only the muscle scars discerned with any certainty on any of the transverse pro preserved on particular bones. cesses. This shows that cervical ribs were probably not present in this taxon. It also seems possible that the cervical ribs have been fusedwith the transverse processes because of Muscles of the scapulocoracoid the old age of the individual. Fig. 28 Fragmentary scapulocoracoids have been preserved in Kryp Pectoral girdle tobaatar (ZPAL MgM-I/41, Fig. 5B, C), Nemegtbaatar (ZPAL MgM-I/81, Figs. 12, l3H-J), Chulsanbaatar (ZPAL Scapulocoracoid. - The scapulocoracoid of ZPAL MgM-I/ MgM-I/lll, Fig. 22B-D) and a taeniolabidoid gen. et sp. 165, referred to by Kielan-Jaworowska (1989) as the left,is indet. ZPAL MgM-I/l65 (Kielan-Jaworowska 1989, Pl. 16:2, actually from the right side. It is incomplete, similar to the and Fig. 19A herein). The bone surface in Kryptobaatarand Nemegtbaatarscapulocoracoid, fromwhich it differsin hav Chulsanbaatar is poorly preserved, and we base our recon ing the ventral arcuate ridge on the blade shorter and less structions (Fig. 28A, C) mostly on Nemegtbaatar and an prominent. The cranial border is keel-shaped proximally, as unidentifiedtaeniolabidoid. in Nemegtbaatar, and the shallow supraspinous fossa (less We do not know the origin of the muscles omohyoideus, obvious than in Nemegtbaatar) is preserved behind it. trapezius p. cervicalis and omotransversarius; omohyoideus FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 41
Fig. 28. DA-C. Right scapulocoracoids. deltoideus p. scapu/aris subscapu/aris DA. Taeniolaboidoid, fam. gen. et sp. trapezius p. cervicali indet. ZPAL MgM-I/165, caudal view. subscapu/aris DB. eitel/us xanthoprymnus(ZIN 159). infraspinatus supraspinatus De. Nemegtbaatar gobiensis (ZPAL infraspinatus MgM-I/81). Reconstructions of muscle omohyoideus attachments based on surface pectoralis abdomina/is topography of bones. B, C, cranial views. Scale bars 5 mm.
triceps brachii c. /ongum
tub. suprag/enoida/e
omotransversarius omotransversarius lig. coracoc/avicu/are B c
in small therian mammals usually inserts on the cranial which there is a depression on the humeri of Nemegtbaatar, border of the scapula, and trapezius p. cervicalis and omo Chulsanbaatar and ?Lambdopsalis (Figs. l3B-E, 23, 29). transversarius insert on the scapular spine at the point of its As in all mammals, m. infraspinatusapparently originated prolongation into the acromion. At this point on ZPAL fromthe infraspinous fo ssa and fromthe caudal surface of MgM-I/81 and ZPAL MgM-Illll there extends a weak the scapular spine. In Nemegtbaatar (Figs. l3I, 28C), Chul longitudinal groove, cranial to which apparently both these sanbaatar (Fig. 22D) and the unidentified taeniolabidoid muscles inserted, and caudaUy originated m. deltoideus p. ZPAL MgM-I/165 (Fig. 28A) on the ventral end ofthe spine, scapularis. there is a craniallysituated rounded surface fo r the origin of The presence of the incipient supraspinous fossa in Nem this muscle, as in, e.g., Antechinus stuarti, Mesocricetus rad egtbaatar (see 'Osteological descriptions') indicates the dei, Citellus xanthoprymnus (Fig. 28B) and many other ex existence of a relatively small m. supraspinatus, although its tant mammals. On the greater tubercle there is a depression scars are recognizable only on the cranial surface of the fo r its insertion, weU seen in the three above-mentioned spine. In extant therian mammals (Gambaryan 1960; multituberculate taxa. We cannot recognize in the studied Jouffroy 1971) it originates on the cranial surface of the multituberculates the origin or insertion of m. teres minor. spine and in the supraspinous fossa and extends onto the In extant mammals the origin of m. triceps brachii caput lateral surface of m. subscapularis; it inserts on the proximal longum is weU seen on the ventral end of the caudal margin end of the greater tubercle of the humerus. There is a de of the scapula. In an unidentified taeniolabidoid, only the pression for m. supraspinatus on the greater tubercle of the ventral part of this origin is visible. A part of its insertion is humeri of all three Mongolian taxamentioned above and in seen in AMNH 1 18505 on the proximal end ofthe olecranon ?Lambdopsalis (Fig. 29). (Fig. 14C-E; see also Figs. 32B and 33B). In Nemegtbaatar In Nemegtbaatar and in unidentifiedtaeniolabidoid sca ZPAL MgM-I/81, on the ventral end of the coracoid there is pulocoracoids we tentatively recognize fo ur weak swellings a thickening, apparently fo r the origin of coracobrachialis, at sites of the origin of the internal aponeuroses of the which extends until the horseshoe-shaped thickening for the subscapularis. Three of them extend longitudinally: along origin ofbiceps brachii, at the base of the coracoid (Fig. 28C). the middle of the highest convexity of the medial side of the Dorsal to the origin of m. coracobrachialis there is a small blade, along the cranial and caudal borders (the latter not concavity, apparently fo r the insertion of m. pectoralis pro preserved in Nemegtbaatar); the fourth is most prominent fundus, delimited ventrally by a narrow ridge for the lig. and extends as an oblique ridge in the ventraI part of the coracoclavicularis. Ventral to the origin of biceps brachii blade, in an arch towards the ventral margin (number l3 in there is a small concavity interpreted as the insertion of m. Figs. 13 H and 28). Ifthis interpretation is correct, this muscle pectoralis abdominalis. Partof m. pectoralis profundusin in multituberculates was quadripennate and extended be serted on the coracoid proeess ventral to the lig. coraco yond the cranial border of the scapulocoracoid. Musculus claviculare (the other part of this muscle inserted on the subscapularis apparently inserted on the lesser tubercle, on humerus - see below). 42 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
Muscles Of the humerus entepicondyle, as characteristic of modem therians, for Figs. 29-3 1 example, Antechinus stuarti and Mesocricetus raddei (Fig. 31). Museulus brachialis originated in ?Lambdopsalis (Fig. In ?Lambdopsalis (Fig. 29) the scars of the insertions of the 29) on the proximal one third of the dorsal surface of the muscles cutaneus trunci, pectoralis superficialis and pecto humerus, between the triceps brachii caput mediale and ralis profundus are recognizable on the wide deltopectoral caput laterale. It did not reach the lesser tubercle, as in most crest. The insertion of pectoralis profunduscontinues up to extant therian mammals (Rinker 1954; Gambaryan 1960; the greater tubercle and passes directly to the coracoid pro Jouffroy 1971; and others). cess. In this respect ? Lambdopsalis differs from therians The areas of origin of the extensor carpi radialis longus, (e.g., Antechinus, Mesocricetus, Meriones and Citellus [Fig. ext. carpi radialis brevis, ext. digitorum communis and ext. 28], studied by us) where the pectoralis profundus passes digitorum lateralis are poorly preserved in ?Lambdopsalis along the intertubercular gro ove to the lesser tubercle and and in the Mongolian taxa, but are weU represented in an then onto the coracoid process. The insertions of m. deltoi unidentified multituberculate fromthe Late Cretaceous of deus p. clavicularis and deltoideus p. scapularis are sepa North Ameriea, AMNH 118267 (Figs. 14B, 30C). Scars for rated in ?Lambdopsalis (Fig. 29). the origin of the extensor carpi ulnaris and supinator were In ?Lambdopsalis (Fig. 29), Nemegtbaatar(Fig. 13A, B) and not seen in all fossil taxa studied by us; however, we recon Chulsanbaatar (Fig. 23A, B) the origin of m. triceps brachii struct them in Fig. 30 by comparison with extant taxa (Fig. caput laterale is weU seen on the deltopectoral crest. Caput 31). As in all recent mammals (Jouffroy1971), these muscles mediale originated in ? Lambdopsalis on the dorsal surface of originated one after the other on the ventral surface of the the humerus; proximally it occupied only the medial part of lateral ectepicondylar crest, but the boundaries between this surface, and distally it extended almost across the whole them are not recognizable and are only tentatively shown in width of this surface up to the epicondyles. In ? Lambdopsalis Fig. 30C. We could not recognize the origin or insertion ofm. (Figs. 29, 30A) m. coracobrachialis apparently inserted by brachioradialis. The origins of two parts offlexor digitorum one head on the ventral side of the humerus reaching prona profundus(si tuated craniodorsal and ventral to fl.digitorum tor teres. On the dorsal side of the entepicondyle (Fig. 30A) sublimis), fl. carpi radialis, fl. carpi ulnaris, pronator teres, there is a distinct area for the origin of m. epitrochleoan palmaris longus and lig. coUaterale mediale are tentatively coneus; this does not extend onto the medial surface of the recognized on the entepicondyles of three taxa in Fig. 30.
supraspinatus tub. minus subscapularis deltoideus p. scapularis infraspinatus
pectoralis profundus
triceps brachii deltoideus c. mediale p. clavicularis ---.IL11/ /" /
latissimus dorsi ---..-r� pectorafis superficiafis teres major cutaneus trunci c
coracobrachiafis __-+. '1 pronator teres Fig. 29. Reconstruction of pronator teres palmaris longus muscle attachments based on surface topography ofbones of fl. digitorum lefthumerus of ?Lambdopsalis profundus __ __ ���__" bulla (NPP V9051), Bayan Ulan fl. carpi ulnaris beds, Early Eocene, Bayan Ulan,
fig. collaterale lig. collaterale Inner Mongolia. DA. Ventrai mediale laterale view. DB. Dorsal view. De. A B Media! view. Scale bar 5 mm. FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 43
Fig. 30. Reconstruction of muscle coracobrachialis pronator attachments based on surface feres f. entepieondylare topography of distal part ofleft (A, C) and right (B) humeri. DA. ?Lambdopsalis bulla (IVPP V8408). DB. Nemegtbaatar gobiensis (ZPAL MgM-I/81). De. Unidentified muItitubercuIate (AMNH 118267), Bug Creek Anthills site, Hell Creek Formation, Montana. Reconstruction of Nemegtbaatar muscles is hypothetical. DAl, B" e. Ventrai views. DA,. Medial view. DA" Bl. Dorsal views. Scale bars 3 mm.
ext. carp; fl. digitorum ulnaris profundus
ex!. digitorum triceps brachii c. mediale communis
f. entepieondylare
ext. carp; radiaJis brevis
ex/. digitorum communis
torum r:,�r�;7; ext. earpi ='" ..,,...... -- ulnaris
supinator
fig. eollaterale laterale
�
ex/. digitorum lateralis fl. earpi fl. digitorum ulnaris profundus c
fl. digitorum profundus epitrochleoanconeus epitrochleoanconeus fl. earpi ulnaris pronator teres
fl. carp; ulnaris
fl. digitorum fl. earpi radiafis sublimis fl. earpi fl. digitorum fl. digitorum radiafis profundus sublimis
ext. digitorum ext. digitorum trieeps braehii ext. digitorum ext. carp; laterafis communis c. mediale radialis
ext. earpi Fig. 31. Muscle attachments on distal ulnaris part of right humeri in extant marsupial and eutherian mammals. DA. Antechinus stuarti (ZIN 1302). supina tor DB. Mesocricetus raddei (ZIN 660). DAl' Bl. Medial views. DA" B, fig. eollaterale laterale Lateral views. Scale bar 5 mm. 44 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
��.---- dorsoepitrochlearis triceps brachii c. longum
triceps brachii c. longum dorsoepitrochlearis
epitrochleoanconeus epitrochleoanconeus --""*l"1ttttll
triceps brachii c. mediale triceps brachii c. mediale
t/1i===tt--'l------fl. carpi fl. carpi ulnaris ulnaris
lig. collaterale mediale
brachialis
brachalis
biceps brachii
fl. digitorum profundus YJ------...... l\--_fl. digitorum c profundus
A B
Fig. 32. Muscle attachments on proximal part ofleftulnae in extant eutherian and marsupial mammals and reconstruction of muscle attachments based on surface topography of multituberculate ulna. Medial views. DA. Mesocricetus raddei (ZIN 660). DB. Unidentifiedmultituberculate (AMNH 118505), Bug Creek Anthills site, Hell Creek Formation, Montana. De. Antechinus stuarti (ZIN 13021). Scale bar 3 mm.
Muscles of the radius and ulna craniolateral surfaces of the olecranon. In this specimen, Figs. 32, 33 insertion of m. epitrochleoanconeus is seen on the medial In Nemegtbaatar ZPAL MgM-I/81, on the proximal part of surface of the olecranon (Fig. 14E, 32B). On the caudal side the radius the tuberosityfor the insertion ofbiceps brachii is of the medial margin the re is a furrow apparently for the developed as a groove, distal to the semilunar articular cir aponeurosis of m. dorsoepitrochlearis. Between it and the cumference (Fig. 14A). The insertions of biceps brachii and insertion of m. epitrochleoanconeus extends the origin of brachialis on the ulna are poorly preserved in Nemegtbaatar. flexorcarpi ulnaris. Most of the medial side was occupied by However, on the ulna AMNH 118505, the insertion ofboth the origin of fl. digitorum profundus,the shape of which is muscles is weU seen distal to the coronoid pro cess (Figs. 14C, more reminiscent of that of Antechinus stuarti than of Meso D, 32B). In many therian mammals m. biceps brachii do es cricetus brandti (Fig. 32). On the lateral surface of the same not insert on the ulna but on a tuberosity on the radius specimen, between the insertion of the medial and lateral (Gambaryan 1960; J ouffroy19 71). Lig. coUaterale mediale in heads of m. triceps brachii, there is a small tuberosityfo r the Nemegtbaatar apparently inserted cranioproximally to the origin of extensor carpi ulnaris. The origin of ext. carpi insertion of m. brachialis, as in therian mammals (Fig. 32). ulnaris do es not reach the origin of ext. poUicis longus (as On the AMNH 1 18505 ulna, caudal to the proximal end of characteristic fo r, e.g., Antechinus stuarti). The origin of ext. the olecranon, there extends along the lateral side a narrow poUicis longus and abductor poUicis lo ngus is more similar furrowfor insertion of m. triceps brachii caput laterale, as in to the condition in Mesocricetus brandti than to that in modem therian mammals (Figs. 14C, 33). Musculus triceps Antechinus stuarti; lig. coUaterale laterale inserted cranial to brachii c. mediale inserted on the cranial, craniomedial and abd. poUicis longus (Fig. 33, see also Fig. 14E). FOSSILS ANDSTRATA 36 (1994) Anatomy and ha bits of multituberculates 45
trlceps brachii triceps brachii brachii c. longum c. laterale
1--"r-"T---_ triceps brachii c. laterale
��:e----\---_ triceps brachii triceps brachii ---f��" c. mediale c. mediale
anconeus ext. carpis ulnaris ----+"'""':----1ft1ffi
fig. coflaterale laterale
fig. coflaterale laterale I-I-I-�-+-- abductor poflicis longus
abductor poflicis longus
ext. pollicis c longus
A B
Fig. 33. Same specimens as in Fig. 32 in lateral views. Scale bar 3 mm.
Muscles of the axial skeleton vertebrae and has a fleshyorigin on the bodies ofthe firstfo ur Figs. 34-41 lumbar vertebrae (Jouffroy & Lessertisseur 1968). Its ten dons ofinsertion are placed at the craniolateral corners ofthe A comparison with extant small therian mammals shows transverse proeesses of the lumbars and on the first sacral that the structure of the lumbar vertebrae depends upon vertebra, dose to the articulation with the ilium. Between the the development of the museuli erector spinae (longissi dorsal surface of the museular origin and the ventral surface mus dorsi, semispinalis dorsi and iliocostalis dorsi). The of the ten dons of insertion there are multipennate musde lengths of the transverse proeesses are correlated with the fibers. In Nemegtbaatar, on the transverse proeesses on the mass of the epaxial museulature (Fig. 47). The interrela right side ofL4 and L7 and the leftside ofL5, there is a distinet tionships between m. longissimus dorsi and semispinalis prominence. We speculate that m. quadratus lumborum dorsi dep end on the distance between the prezygapophysis inserted by internal aponeurosis on the ventral side of the and the spinous pro cess (Figs. 34, 36). On the ventral side craniolateral corners ofthe transverse proeesses and was very of the lumbar vertebrae there are, in therians, three strong (Figs. 34A, 35, 39B). musdes: psoas minor, psoas major and quadratus lum The dorsal part of the epaxial museulature is complex in borum (Fig. 34B). There is a high ventral crest on the ven extant therian mammals (Slijper 1946; Jouffroy& Lessertis tral surface of L2 in Nemegtbaatar. In extant mammals a seur 1968). Museulus interspinalis consists of right and left prominent ventral crest (referred to as the ventral spinous bundles of fibersthat extendbetween the spinous proeesses proeess) occurs only among leporids, in which m. psoas of two consecutive vertebrae. The right and left bundles major is strongly developed. (dorsal view) are separated by a vertical ten don (Fig. 36A). In extant mammals m. quadratus lumborum arises by The presenee of the medial and lateral ridges on the caudal ten dons from the bodies of the last two or three thoracic surface of the spinous pro cess in Nemegtbaatar (ZPAL 46 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS ANDSTRATA 36 (1994)
longissimus dorsi semispinalis dorsi intermetapophysis semispinalis dorsi
proe. spinosus
saeroeaudalis dorsalis
longissimus dorsi
ilioeostalis
····HITI+_-aorta r----- quadratus lumborum
---- psoas major -----"+�
ilioeostalis psoas minor A B
Fig. 34. DA. Nemegtbaatar gobiensis. Reconstruction oftransverse section ofvertebral column at leve! ofLS; DB. Same region in Meriones blackleri. Scale bar IO mm.
MgM-I/8l), seen only on 13 and L4 (the remaining spinous processes are badly damaged), indicates that m. interspinalis (inserted between the ridges) and the vertical tendon were well developed (Fig. 36B, see also Fig. 11). In Nemegtbaatar, m. intertransversarius was apparently weakly developed, as the insertion area for this muscle, on the cranial surface of the transverse pro cess is very small (Figs. 11, 36B). Musculus intermetapophysis (intermamillaris) in rodents studied by us (Figs. 34B, 36A) arises on the cranial side of the metapophyses of Sl and all the lumbars, and is inserted on the caudal side of these metapophyses. In addition, on L6 to 11, between the metapophyses and anapophyses of every proc. spinosus other vertebra (e.g., metapophysis ofL6 - anapophysis ofL4; metapophysis of L5 - anapophysis L3), there extends an other branch ofthis muscle. In mammals that have this latter muscle developed (for example in all extant taxa cited in Table 2), the metapophyses show, in dorsal view, both me dial and lateral deviation. Musculus intermetapophysis was B apparently not present in Nemegtbaatar (Figs. 34A, 36B). The metapophyses are absent in Nemegtbaatar, but the pre zygapophyses (which on the right side ofL7, leftL6 and L4 have dorsal surfaces well preserved) , do not show the medial deviation characteristic of this muscle (Fig. 36B). Fig. 35. DA, B. Nemegtbaatar gobiensis We conclude that the tail in Nemegtbaatar (not preserved) (ZPAL MgM-I/81). Reconstruction of was very long. In rodents and some insectivores (for example m. quadratus lumborum and its apo- Ellobius, Talpa) with a short tail, m. sacrocaudalis dorsalis A neuroses, based on surface topography of the bones. DA. Dorsal view. DB. do es not reach the lumbar vertebrae. In mammals with a Sagittal section. Scale bar 10 mm. medium-size tail, this muscle arises from the metapophysis FOSSILS ANDSTRATA 36 (1994) Anatomy and habits of multituberculates 47
proc. trans versus proc. spinosus postzygapophysis cyon) this muscle also reaches the last thoracic vertebrae. In Nemegtbaatar this muscle originated from thecaudal mar gins ofthe prezygapophyses ofthe last four lumbar vertebrae (the upper arrow in Fig. llA). As the anterior lumbars are damaged, it cannot be stated whether sacrocaudalis dorsalis continued more cranially; it is tentatively reconstructed in Figs. 34A, 36B, 39, 40B, 4lA. The ventraI side of the sacrum has not been exposed in Kryptobaatarand Nemegtbaatarand could be examined only in Chulsanbaatar (Fig. 2lB). The laterocaudally directed ridge on the transverse pro cess of Sl apparently formed the cranial boundary of the insertion of m. sacrocaudalis vent ralis. If this were true the muscle would not extend onto the lumbars (Fig. 39, 40, 4lA). Musculus longissimus dorsi is the largest of the epaxial musculature in small extant mammals (Rinker 1954; Jouf froy & Lessertisseur 1968). It arises from the medial and cranial surfaces of the ilium (two upper left arrows in Fig. l6E) and inserts on the dorsal surface of all the transverse processes of the lumbar vertebrae and also on the anapo physes. In Nemegtbaatar there are no anapophyses, but on the pedicles, below the medial sacral crest, the re is a weak longitudinal ridge, convex upwards. This ridge corresponds to the origin of m. longissimus dorsi, which extended from the ilium cranioventrally and then in an arch craniodorsally, below m. sacrocaudalis dorsalis (Figs. 34A, 37A, 39, 40, 4lA, see also Fig. 11). The part of this muscle that in modem mammals arises fromthe spinous processes and inserts on the thoracic vertebrae could not be reconstructed, as the spinous processes are damaged, and the thoracic vertebrae are not preserved. Musculus semispinalis dorsi originated in Nemegtbaatar fromthe cranial end of the prezygapophyses that are medially deviated (the lower arrow in Fig. lIA and Figs. 34A, 36B, 39, 40).
Muscles of the pelvie girdle and hind limb Our reconstructions of the pelvic and hind-limb muscula ture ofMongolian taxa differin details fromthose presented by Simpson & Elftman(19 28) for ?Eucosmodon. We follow Fig. 36. Reconstruction of muscle attachments based on surface topogra Gambaryan' s (1974) division of the hind-limb musculature phy of the last lumbar vertebrae. Cranial to the right. DA. Meriones in therian mammals, which provides the basis fo r functional tamariscinus (ZIN 428), lateral view. DB. Nemegtbaatar gobiensis (ZPAL MgM -I/8l). Al' Bl' dorsal view. A" B" lateral view. Dashed and dotted lines analysis. in B, indicate the two tentative reconstructions ofthe lengths ofthe spinous proeesses. Reconstructions based on originally preserved more complete spinous proeesses (now broken) in ZAPLMgM-I/81 and on relatively long Muscles of the hip joint (partly broken) spinous proeesses of L6 and L7 in Kryptobaatar(F ig. 2). Figs. 37-44 Scale bar 10 mm. Gambaryan (1974) recognized the following groups of muscles of the hip joint: flexors (rectus femoris, iliopsoas); ofthe two posterior lumbars (Microtus, Microgale). In mam three groups of extensors: gluteal group (gluteus super mals with a long tail, m. sacrocaudalis dorsalis arises fromthe ficialis, gluteusmedius, gluteus profundus and piriformis), metapophyses of all the lumbars (Figs. 34B, 36A). In rico short postfemoral muscles (pectineus, add. longus, add. chetal mammals with a very long tail (Allactaga, Rhyncho- brevis, add. magnus, praesemimebranosus and quadratus 48 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
semitendinosus biceps femoris acetabulum rectus femoris gluteus medius posterior
obturator extemus
quadratus longissimus femoris dorsi obturator
semimembranosus posterior adductor brevis f. postobturatum
gluteus superficialis
obturator internus
obturator externus gemelli acetabulum biceps femoris rectus femoris posterior
f. obturatum
acetabulum pectineus
adductor longus adductor brevis gluteus profundus gracilis "----' quadratus femoris 81 adductor magnus 82
biceps femoris obturator internus posterior
semitendinosus f. obturatum f. obturatum acetabulum c FOSSILS AND STRATA36 (1994) Anatomy and habits of multituberculates 49 femoris); short muscles of the trochanteric fossa (obturator iliosacral contact, originated from the ventrolateral surface externus, obturator intern us, gemelli cranialis and gemelli of the ilium (Fig. 37 A). In this respect multituberculates caudalis); long postfemoral muscles (biceps femoris, graci differfrom small extant therian mammals, e.g., Antechinus lis, semitendinosus, semimembranosus and tenuissimus - and Meriones, in which iliacus originates from the ventrai the latter not always present). Museulus psoas minor, which part ofthe lateral side ofthe ilium (Fig. 38). Iliacus inserted in we also describe below, does not belong to the above de multituberculates on the lesser trochanter, apparently by a finedgroups. common tendon with psoas major (as in extant mammals), In extant mammals (for example in those cited in Table 2) and is not shown in Fig. 42. m. psoas minor arises from the middle part of the ventrai Cluteal group (Figs. 37-42). - In Nemegtbaatar the area of surface of the last thoracic and first lumbar vertebrae; it origin of m. gluteus superficialis extended continuously inserts on the psoas tubercle of the pubis (Fig. 38). We were along the ventrai margin of the iliac wing from the caudal unable to findits origin in studied multituberculates. How ventral iliac spine to the cranial end of the ilium (Fig. 37 A). ever, in Nemegtbaatar we fo und its insertion at the cranial The origin of this muscle on the wing of the ilium shows that end of the transverse ridge of the dorsal part of the pubis it was not divided as yet into tensor fasciae latae and gluteus (Figs. 16F, 37 Al) where at the cranial part ofthis ridge there ' superficialis. Therefore we reconstruct these two muscles as is a small tuberosity with a small depression dorsal to it. one muscle (Fig. 40A). In extant therian mammals, as a rule, Apparently the insertion of this muscle was both tleshyand gluteus superficialisarises also fromthe gluteal fascia, which tendinous. The dorsal concave side ofthe described structure extends between the spinous proeesses ofthe last lumbar and corresponds to the tleshy area of attachment, while the firstcaudal vertebrae (Fig. 38). Apparently this was also the cranioventral tuberosity corresponds to the tendinous at case in the studied multituberculates, as indicated by the tachment. In extant mammals the insertion of this muscle is inferred site of insertion of this muscle, which extends con tendinous; the apparent tleshy-tendinous insertion in mul tinuously distally along the lateral edge of the femur; the tituberculates possibly represents a more primitive stage. distal boundary ofthe insertion area could not be recognized Flexors of the hip joint (Fig. 37-42). - Museulus rectus femo (Figs. 16A, B, 40A, 41C, 42C, D). Musculus sartorius, recog ris in all of the studied multituberculates originated from a nized by Simpson & Elftman(19 28) in ?Eucosmodon, was not shallow, round depression situated cranial to the small node developed in multituberculate taxa studied by us. with a pit that lies directly in front of the margin of the Musculus gluteus profundusin studied multituberculates acetabulum (Figs. 2, 16F, 37A, B, 39A, 40B, 41B). In most was surrounded dorsally, laterally and ventrally by gluteus extant mammals this area of attachrnent is developed as a medius (Figs. 37AI_3, B2, 39, 40, 41C). The area of origin of tuberosity (Fig. 38). The presenee of a depression for the gluteus profundus is clearly seen on the lateral surface of the origin of rectus femoris in multituberculates suggets that its ilium (right arrows in Fig. 16D); dorsal and ventral to it there origin was tleshy. is an apparent area ofattachment ofgluteus medius up to the We were unable to recognize the origin of m. psoas major boundary with the attachment of gluteus superficialis (Fig. in studied multituberculates. However, the ventral crest pre 37A); the dorsal origin of gluteus medius extends along the served on the body ofL2 in Nemegtbaatarindicates a strong longitudinal ridge on the dorsal side ofthe ilium «(leftarrows development of this muscle. This conclusion is also sup in Fig. 16D and right arrows in Fig. 16E). In Nemegtbaatar ported by an apparent area of its insertion on the lesser the area of attachment of gluteus profundus extended cau trochanter, which in all multituberculates is very prominent dally as far as the area of origin of rectus femoris, and gluteus (Figs. 2B, 16A, C, 21A). Psoas major probably inserted on the medius (in dorsal view) extended up to the middle of the medial side of the lesser trochanter (Fig. 42A-C). Museulus medial side of the thickened margin of the acetabulum (Fig. iliacus in multituberculates, because of the dorsoventral 37A). In many small extant mammals, in contrast, gluteus profundus extendsmore caudally than gluteus medius (Fig. 38). In all studied multituberculates it was impossible to establish the origin of m. piriformis, which occurs in small extant eutherian mammals (Fig. 38A). The insertions of Fig. 37. Reconstruction of muscle attachments based on surface topogra phy of multituberculate pelves. DAl' Nemegtbaatargobiensis (ZP ALMgM gluteus medius, gluteus profundusand piriformis are clearly I18l ). Lateral view of pelvis. DA,. Latroventral view ofiliac wing ofA l' DA3• seen on the greater trochanter (especially in Nemegtbaatar) Dorsal view of anterior part of Al' OBl' Chu/sanbaatar vulgaris (ZPAL and along the lateral edge of the femur (Figs. 16B, 42C, D). MgM-I/99a). Caudal part of pelvis, lateral view. DB2• Chulsanbaatar vul Musculus gluteus profundus inserted on the most medial garis (ZPAL MgM-I185). Almost entire pelvis, lateral view. DC Sloan baatar mirabilis (ZPAL MgM -I/20). Lateral view of the posterior part ofthe part of the rugose area of the greater trochanter; proximal to pelvis. DDl. Kryptobaatar dashzevegi (ZPAL MgM-I/41). Lateral view of it, on the top of the trochanter, inserted the piriformis; the pelvis (mirror image ofleftside) and caudal vertebrae. OD,. Dorsal view of gluteus medius extended from the top of the trochanter posterior part of Dl, slightly inclined to leftside (mirror image). Straight along the lateral edge of the femur, up to the contact with lines in B2 and DI indicate long axes ofilium, ischium and sacrum. Iliosacral angle is between long axes ofilium and sacrum. Scale bars 3 mm. (See Fig. gluteus superficialis.The boundary between the insertion of 38 for comparison with extant marsupial and eutherian mammals.) these two muscles is not clear. 50 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
semitendinosus presemimembranosus piriformis g/uteus medius g/uteus profundus
biceps femoris anterior
biceps femoris posterior
iliacus psoas minor A semimembranosus adductor /ongus posterior
adductor bre vis quadratus femoris
semitendinosus biceps femoris anterior tenuissimus g/uteus profundus g/uteus supeficia/is g/uteus presemimembranosus medius
biceps femoris iliacus posterior Icrr---- psoas minor quadratus femoris /'.."""'1----- pectineus
HlT���---_ obturator externus -� obliquus abdominis externus graci/is B magnus rectus abdominis
Fig. 38. DA, B. Muscle attachments on pelvis in extant eutherian and marsupial mammaIs, lateral view. Last lumbar vertebrae, sacrum and first caudal vertebrae diagrammatically illustrated as tube. Musculi erector spinae and m. sacrocaudalis dorsalis, on which fasciae of the pelvic muscles originate, are not shown in this figure. DA. Meriones blackleri. DB. Antechinus stuarti. Scale bars 5 mm.
5hort postfemoralmus cles (Figs. 37--42). - In multitubercu Musculus adductor longus in Nemegtbaatar (Figs. 37A I' lates m. pectineus originated froma rounded, relatively large 41A, B) originated from the cranioventral margin of the area of the pubis, below the transverse ridge that extends pubis, immediately ventral to m. pectineus, and surrounded cranially fromthe lower margin of the acetabulum. This area the area of articulation with the epipubic bone. It covered the is comparatively larger in Chulsanbaatar than in other gen cranial part of the origin area of m. graciIis, the craniodorsal era (Fig. 37B1). This muscle inserted along the proximal half part of which extended between add. longus and add. of the medial edge of the femur and was relatively strong in magnus. In Chulsanbaatar, gracilis apparently did not ex multituberculates (Fig. 42A, B). tend between add. longus and add. magnus (Fig. 37B1 ). FOSSILS AND STRATA 36 (1994) Anatomy and ha bits of multituberculates 51
Fig. 39. Nemegtbaatar gluteus longissimus gobiensis (ZPAL MgM-I/81). superficialis dorsi DA. Transverse section of semispinalis dorsi pubic region in frontof acetabulum, at leve! of 53. semispinalis ----I!u: : proc. transversus DB. Transverse section of dorsi ilium at leve! of L? 5cale sacrocaudalis proc. spinosus bars S mm. dorsalis ----T��QIj]nt\s
gluteus medius sacrocaudalis gluteus profundus dorsalis
sacrocaudalis ventralis ----+---li=� quadratus lumborum ---+---+-1:4=H..rr� A psoas major ilia cus
adductor magnus pubis iliacus B proc. transversus
rectus femoris
Adductor longus inserted on the ventral side of the femur, tuberculate specimens described here. However, on the fe immediately lateral to the insertion of pectineus (Fig. 42A, mur of Nemegtbaatar, we infer that the area of insertion is B). Adductor magnus in Nemegtbaatar originated fromthe situated medial to the origin ofgastrocnemius medialis (Figs. ventral part of the lateral side of the pubis and ischium, 17D, 42A, B). The caudofemoralis identifiedby Simpson & immediately dorsal to gracilis and add. longus; add. magnus Elftman (1928) in ?Eucosmodon is not homologous to the reached with its cranial end the level ofpectineus (Fig. 37 AJ muscle described by us under the same name. Musculus In Chulsanbaatarit did not extend so far dorsally (Fig. 37B1). caudofemoralis of Simpson & Elftman corresponds to the
Adductor magnus in Nemegtbaatar inserted on the ventraI caudal part of gluteus superficialis ( = femorococcygeus of side ofthe femur, occupying a large area (about two thirds of Dobson 1882-1890; Jouffroy 1971 and others). the ventral surface of the femur) between the lateral and See also Figs. 40, 41 for the reconstruction of the above medial borders (Fig. 42A, B). Adductor brevis in Nemegtbaa discussed muscles and Fig. 38 fo r comparisons with extant tar and Chulsanbaatar (Figs. 37Al' Bl) extended from the mammals. ventraI part of the lateral side of the ischium, immediately to the rear of add. magnus, surrounding the postobturator Longpostfemoral muscles (Figs. 37-41, 43). - Musculus graci fo ramen (or notch), characteristic of multituberculates. Ad lis originated in studied multituberculates fromthe area in ductor brevis inserted on the lateral margin of the fe mur, front of the postobturator notch on the ventral keel of the distal to the lesser trochanter, as far as midway along the pelvis and extended along the ventraI margin of the pubis. In femur to a point between the insertions of add. magnus and Chulsanbaatar it reached the caudal margin of adductor gluteus superficialis (Fig. 42B, C). longus, whereas in Nemegtbaatar it entered between the Musculus quadratus femoris in Nemegtbaatar (Fig. 37A l) bellies of add. longus and add. magnus (Fig. 37AI, Bl). In originated fromthe ischium, among the following muscles: most extant mammals, as a rule, gracilis is the most medial semimembranosus anterior, semimembranosus posterior, muscle of the thigh group (ventral in Fig. 38) and is not add. brevis, obturator externus and gemelli. It inserted on the covered by other muscles. However, in Allactaga and Sorex, medial side ofthe lesser trochanter ofthe femur (Fig. 42B, C). for example, we fo und gracilis in a position similar to that in The insertion area on the trochanter is surrounded by a weak Nemegtbaatar (Fig. 41A, B), i.e. covered laterallyby adductor ridge, on which there are small transverse ridges, apparently longus. We conclude, therefore, that in multituberculates indicating the multipennate structure of this muscle. gracilis did not extend onto the epipubic bone. This is unlike Musculus praesemimembranosus (caudofemoralis) in the condition in Ornithorhynchus and Tachyglossus, where it small extant mammals, as a rule, originates fromthe spinous does extend onto the epipubic bone (Gregory & Camp or transverse processes of the sacrum (Fig. 38). We were 1918). In Antechinus (Fig. 38B) it extendsonly to the proxi unable to identify its site of origin in any of the multi- mal part of the epipubic bone. In Nemegtbaatar, gracilis 52 Zofia Kielan-Jaworowska & PetT P. Gambaryan FOSSILS AND STRATA 36 (1994)
g/uteus superiicia/is and tensor fa sciae /atae
.�==lrlt----- semispina/is dorsi
�/1---- /ongissimus dorsi sacrocauda/is
g/uteus medius semitendinosus ��&------� adductor brevis
adductor magnus
biceps femoris
A fl. digitorum brevis
semitendinosus g/uteus profundus g/uteus medius semispinalis dorsi
coccygeus sacrocaudalis �!'7--__ dorsa/is sacrocaudalis dorsalis /ongissimus dorsi sacrocauda/is ventra/is psoas major
gemelli cauda/is quadratus femoris adductor brevis adductor magnus semimebranosus posterior semimembranosus anterior gastrocnemius /atera/is
fl. digitorum B fib u/aris
tendo m. peronei/ongi FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 53 inserted on the medial side ofthe tibia in the long groove that Short muscles of the trochanteric fo ssa (Figs. 37, 38, 41A, C, extends along two-thirds of the tibial length and continued 42B). - Musculus gemelli originated from thedorsal side of more proximally than, fo r example, in Antechinus. the ischium. At the dorsal margin of the ischium there is in Musculus biceps femoris posterior (we were unable to Nemegtbaatar a small oval concavity for accommodation of reconstruct biceps femoris anterior) and semitendinosus are the tendon ofm. obturator intern us (Fig. 37Ad. In general only tentatively reconstructed here fo r Nemegtbaatar. We this tendon in extant mammals divides the attachment of reconstruct them as originating fromthe ischial tuber: biceps gemelli into gemelli cranialis and gemelli caudalis. In studied femoris posterior cranially, semitendinosus caudally (Fig, multituberculates this division was not complete. The area of 37 AI)' The reason for such a reconstruction is the presence of the origin of obturator internus is clearly seen in Kryptobaa well-preserved areas for the ventral part of the attachment of tar (Fig. 3 7D2), and on this basis we reconstruct it in Nemegt these muscles in Sloanbaatar (Figs. 26B, 37C) and, less baatar (Fig. 41A). It originated from themedial surface of the clearly, in Chulsanbaatar (Fig. 37BI). It appears that in mul ischium and ran along the border of the obturator fo ramen tituberculates semitendinosus also had a vertebral head on dorsocaudally. Its tendon embraced the ischium dorsally the sacral and caudal vertebrae (Fig. 40). In most extant and partially extendedonto the femur. Musculus obturator mammals this muscle has two heads (one ischial and one externus originated froma large area on the lateral side of the vertebral, Fig. 38). Verheyen (1961) believed that absence of pubis and ischium, ventrocaudally to the obturator fo ramen the vertebral head is related to swimming habits, as he noted (Figs. 37AI, BI' 41C). In extant mammals the short muscles in, e.g., Potamogale and Micropotamogale. There is no reason of the trochanteric fossa insert in this fo ssa. As a rule, obtura to postulate that the vertebral head disappeared in studied tor internus is situated most proximally; distally to it insert multituberculates, although Simpson & Elftman (1928) both gemelliand most distally obturator externus (Fig. 38). believed that it was not present in ?Eucosmodon. Semitendi Apparently, this musculature inserted in studied multituber nosus apparently inserted in the same groove as gracilis, on culates in a similar way. the medial side ofthe tibia. In Nemegtbaatarthe distal end of this groove widens, apparently fo r insertion of this muscle (Figs. 41A, B, 43C, D). In extant mammals semitendinosus Muscles of the knee joint and gracilis insert in the wider part of this groove. The site of Figs. 37-42, 44 insertion of biceps femoris posterior is not visible on the Extensors of the knee joint. - Musculus quadriceps femoris in bones of extant mammals and has not been recognized in mammals (Fig. 38) consists of fo ur heads, three of which studied multituberculates. Possibly, as in extant mammals (vastus lateralis, vastus medialis and vastus interrnedius) (e.g., those cited in Table 2), this muscle inserted in Nemegt originate from the femur and the fo urth (rectus femoris) baatar on the ventrai (cranial) side of the tibia, continued on fromthe ilium. The latter has been described above as one of the fascia cruris and possibly on the common calcaneal the flexorsof the hip joint. Musculus rectus femoris and the tendon (Fig. 40A). three heads ofvastus work together as extensors of the knee. Musculus semimembranosus anterior arises froma large In Nemegtbaatar the area of origin of vastus lateralis is well area on the caudal part of the ischium in a variety of recent preserved. This muscle originated as an aponeurosis from therians (Fig. 38). From the size ofthis area in multitubercu the crenulated ridge on the trochanter major, distal to the lates one can infer that this muscle was especially strongly insertion ofgluteus profundus, andextended mediallyto the developed (Fig. 37 AI' BI)' It inserted on the well-definedarea subtrochanteric tubercle. Distal to the subtrochanteric on the medial side of the proximal end of the tibia (arrow in tubercle, m. vastus lateralis fits tightly with vastus medialis. Fig. 17I). As the tubercle for the lig. collaterale mediale is The area of origin of these two muscles occupied the proxi situated distally, and its central area is elongate, we conclude mal one-third of the dorsal surface of the femur. The distal that semimembranosus anterior passed under this ligament one-third ofthis surface was occupied by the area of attach (Figs. 4IB, 43C, D). Musculus semimembranosus posterior ment ofvastus intermedius (Figs. 41A, B, 42A, C, D). Allfo ur originated fromthe ischium, ventral to semimembranosus heads apparently inserted on the patella, which, in the stud anterior, and was surrounded cranially by add. brevis and ied multituberculates, has been preserved only in Chulsan dorsally by quadratus femoris. It inserted on the medial side baatar (Fig. 24B, C). of the tibia, ventral (cranial) to the insertion ofpopliteus and distal to the lig. collaterale mediale (Fig. 43C, D). Flexors of the knee joint. - Musculus popliteus apparently originated in Nemegtbaatar (Figs. 17C, 41B, 42C, 43C, D), fromthe ventral part of the lateral epicondyle of the fe mur (as in modern therian mammals). Its insertion on the Fig. 40. Nemegtbaatar gobiensis. Reconstruction of muscles of right hind mediocaudal surface of the tibia was triangular in shape, limb, lateral views. DA. Superficial layer. Musculus gluteus superficialis and tensor fasciae latae reconstructed as one muscle (see p. 49). DB. Deep distally tapered and occupied the proximal one third of the layer. Scale bar 10 mm. tibial surface. 54 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
sacrocauda/is ventralis obturator internus sacrocaudalis dorsa/is
/ongissimus dorsi
psoas major
tensor fa sciae /atae semimembranosus anterior ----.-:>� ::--.,;��-- vastus media/is
semimembranosus posterior adductor magnus
semimembranosus anterior semitendinosus ------��
gastrocnemius medialis caput ossis femoris semimembranosus f. obturatum posterior A
gemelli crania/is
gemelli rectus femoris cauda/is
adductor magnus
vastus medialis
��tfillf---__ semimembranosus anterior
adductor brevis pop/iteus g/uteus superficialis
gastrocnemius media/is semitendinosus femur B c
Fig. 41. Nemegtbaatargobiensis. DA, B. Mirror images of reconstructions of muscles of right hind limb in media! views. DA. Superficia!layer.DB. Deep layer. De. Reconstruction of muscles of right hind limb in ventrocaudal view. Scale bar 10 mm. FOSSILS AND STRATA 36 (1994) Anatomy and ha bits of multituberculates 55
g/uteus medius gemelli piriformis piriformis ------, caudalis g/uteus medius ---.�_ g/uteus medius ---,;v obturator internus gemellicrania/is obturator externus --*-+-----',." g/uteus profundus psoas major psoas 'S'J+IIIll#t--- g/uteus superficialis pectineus -----4-l:1
V/,",--,,"-- vastus media/is vastus /atera/is adductor /obngus adductor brevis vastus media lis adductor magnus
vastus intermedius J----"'II--_ adductor magnus vastus intermedius presemimembranosus k.,.,.---i
ext. digitorum gastrocnemius /ongus medialis
A B D Fig. 42. Reconstruction of muscle attachments based on surface topography of right femur in Nemegtbaatar gobiensis, proximal two thirds based on ZPAL MgM-I/81, distal part on ZPAL MgM-II110 (reversed). DA. Medial view. DB. Ventrai view. DC Lateral view. OD. Dorsal view. Scale bar 5 mm.
Muscles Of the tarsal joint proximal end of the fibulathere is a surface evidently corre Figs. 40-44 sponding to the origin ofm. soleus. This surface abuts against In Nemegtbaatarm. gastrocnemius medialis originated, as in the surface of the origin of gastrocnemius lateralis on the modem therians (Jouffroy 1971), from the medioventral parafibula, as reconstructed in Figs. 43A, B, 44A. It seems surface of the femur, in a shallow depression proximal to the that in studied multituberculates soleus was not completely medial condyle (Figs. 17E, 42A, B). The area of origin of this separated from gastrocnemius lateralis. Musculus plantaris muscle has not been exposed in Kryptobaatar. possibly was not present in the studied multituberculates, In all eutherians m. gastrocnemius lateralis originates and this condition is also characteristic of monotrernes fromthe femur (Jouffroy 1971). In some extant marsupials, (Haines 1942). On the calcanea fromthe Late Cretaceous of e.g., Antechinus stuarti (Fig. 44B), gastrocnemius lateralis North America (Fig. 55F-I) and in ?Eucosmodon (Fig. 56H originates not fromthe femur but fromthe parafibula. The J), which are better preserved than in studied Mongolian parafibula has been preserved in Kryptobaatar(F igs. 2, 3A, multituberculates, there is no tuberosity on the tuber calca B, 44A), Chulsanbaatar (Fig. 24B, C) and an uncertain frag nei fo r its insertion. ment in Nemegtbaatar (Fig. 17F, H, I). The area of the origin of gastrocnemius lateralis is seen on the parafibulain Kryp Muscles of the foot tobaatar, where there is a distinct concavity for its origin (less Figs. 40, 42, 43 obvious in Chulsanbaatar). As in A. stuarti, in studied multi Long extensors.- Musculus tibialis anterior originated on the tuberculates the parafibula was probably connected by a large part of the laterocaudal surface of the tibia and cranio strong ligament with the patelIa, which has been preserved medial surface of fibula and at the prominent, triangular, only in Chulsanbaatar (Fig. 24B, C). Gastrocnemius latera hooked processes on the lateral side of the proximal ends of lis, which originates on the parafibula in A. stuarti (on the these bones in Kryptobaatarand Nemegtbaatar (Figs. 2, 17F, dorsal side of which inserts lig. parafibularo-patellare) acts H, 40B, 43A-C). In contemporary mammals (e.g., Antechi as extensor of the knee joint and assists in the extension of nus and in Meriones, personal observations) this muscle the tarsal joint (referred to as flexionin human anatomy, see originates fromthe proximal one-third of the tibia, fromthe Davies & Davies 1962). We conclude that in studied multi fascia of peroneus longus, and on the proximal part of the tuberculates gastrocnemius lateralis acted as in A. stuarti fibula. In Kryptobaatarand Nemegtbaatar, between the two (Fig. 44B). tendons that originated fromthe lateral hooked processes of In Nemegtbaatar (Figs. 17F, H, 43A, B) and, less obvious, the tibia and fibula,a tendon of ext. digitorum lo ngus passed in Kryptobaatar (Fig. 2) on the laterocaudal part of the onto the femur. Its course is more apparent in Kryptobaatar 56 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
biceps femoris peroneus /ongus semimembranosus anterior
fig. col/atera/e tibiafis posterior laterale so/eus
fig. col/atera/e pop/iteus media/e 1-I,'A1IlIrA"lI'- so/eus pop/iteus
peroneus brevis peroneus digiti fig. col/atera/e peroneus digiti quinti media/e quinti semimembranosus semimembranosus ext. hal/ucis posterior posterior /ongus fl. digitorum ---1'<1 tibiafis gracifis
peroneus semitendinosus tibiafis anterior brevis
fl. digitorum fibu/aris peroneus digiti biceps quarti femoris fl. digitorum tibiafis tibiafis anterior fl. digitorum fibu/aris
Fig. 43. Left tibia and fibula.Reconstruction of muscle attachments based on surface topography ofbones in Nemegtbaatar gobiensis (ZPAL MgM-I/I IO). DA. LateraL DB. CaudaL DC CraniaL OD. Medial views. Scale bar 5 mm. than in Nemegtbaatar. In the latter these hooked processes are very dose to each other, but area of the origin of the ten don of ext. digitorum longus at the lateral epicondyle of the fe mur (Fig. 42C) demonstrates the existence of this tendon. In Kryptobaatar m. tibialis anterior inserted on a fovea at the mediodorsal surface of the entocuneiform and femur parafibula lig. patellaro possibly on the proximal end of Mt I (Fig. 7E). Extensor parafibufare digitorum lo ngus originated from the lateral epicondyle of the femur (Fig. 42C). In most modem mammals there are two sites ofinsertion ofthis musde. As a rule it inserts directly on the ungual phalanges or on the distal ends of Ph 2 ofD Il - D N. In Kryptobaatarthis musde possibly inserted directly femur onto the ungual phalanges. tibia fibula Extensor hallucis lo ngus is large in contemporary climb ing mammals. In non-dimbing mammals it is small, and fig. patellarofibulare lig. collaterale there is no trace of its origin on neither the fibula nor the laterale ----f!.?---lil: patefIa tibia. We have not fo und such a trace in Nemegtbaatar or fig. patel/are peroneus digiti Kryptobaatar, but this does not exdude the possibility of its quinti ------\---l\-.l!I lig. cruciatum presence, and we tentatively reconstruct it in Fig. 43A. caudale lig. collaterale Musculus peroneus longus originated in Nemegtbaatar fibula mediale and Kryptobaatar from the lateral side of the triangular tibia hooked process of the fibula, immediately lateral to the origin of soleus (Fig. 43A, B). This musde lies in a fissure Fig. 44. Reconstruction of origin of m. gastrocnemius and tendons on fo und only on the leftfibula in Kryptobaatar (to the right and parafibulain multituberculates and mars upi als. DA. Kryptobaatardashze vegi; AI' A, lateral and medial view. DB. Antechinus stuarti; BI' tibia in below the number 12 in Fig. 2B). In other specimens this part lateral, fibulain cranial view; B2, tibia in medial, fibulain caudal view. Scale of fibulais broken. Peroneus longus in Kryptobaatarappar- bar 5 mm. FOSSILS AND STRATA 36 (1994) Anatomy and habits of multitubereulates 57 ently passed through the peroneal groove in the calcaneum tions frommost small modem therian mammais. Because of onto the plantar side of Mt V (number Il in Fig. 2B), but we limb abduction, their body was held lower to the ground were unable to reconstruct its further course. However, we than in mammals with more parasagittally oriented limbs reconstructed the course of the tendon of m. peroneus and is similar in proportions to that reconstructed for Gobi longus in ?Eucosmodon (see Fig. 57B and 'Functional anato conodon (Jenkins & Schaff 1988, Fig. l). A characteristic my'). Musculus peroneus brevis originated fromthe medial feature of the multituberculate body is the relatively large side of the fibula,starting near the origin of peroneus longus head and short neck. For example, in Kryptobaatarthelength and covering about "15 of the length of this bone. Peroneus of the skull is 34 mm, which corresponds to 600% of the brevis passed through a sulcus situated cranial to peroneus length between pre- and postzygapophyses ofL7. In Nemegt longus. In Kryptobaatar it inserted at a bulge at the latero baatarthe length of the skull is 40 mm and the width 31 mm, proximal end of Mt V, and on this basis we reconstruct it in which corresponds to 570% and 440%, respectively, of the Nemegtbaatar (Fig. 40B). Peroneus digiti quarti and peron length between pre- and postzygapophyses ofL7. In marsu eus digiti quinti originated in Nemegtbaatarand Kryptobaa pials, the same proportions are 563% and 287% in Didelphis tar on the lateral surface of the fibula between soleus and marsupialis and 360% and 220% in Phalanger maeulatus; in peroneus brevis, peroneus digiti quarti more distally than rodents the proportions are 425% and 300% in Spermo peroneus digiti quinti (Fig. 43A, B). The sites of insertions of philopsis leptodacytlusand 445% and 210% in Rattus norvegi these muscles were not fo und, and the insertion of peroneus eus; while in Gobieonodon ostromi (measured in the recon digiti quinti is only tentatively reconstructed in Fig. 40B. struction in Fig. l ofJenkins & Schaff1988) the length of the skull is 660%. Longflexors.- Musculus tibialis posterior, fl.digitorum tibia In comparison to the length ofthe femur, the length of the lis and fl.digitorum fibularis in Kryptobaatarand Nemegt skull is 140% in Kryptobaatar, 126% in Didelphis mar baatar originated on the intemal surface of the tibia and supialis, 97% in Phalanger maeulatus, 120% in Spermophil fibula and fromthe interosseous membrane (Fig. 43C, D). opsis leptodacytlus, 125% in Rattus norvegieus and 181% in Flexor digitorum fibularis originated laterally and fl.digi Gobieonodon. torum tibialis medially. In extant mammals, a part of this It follows that the multituberculate skull is relatively latter muscle usually originates distal to popliteus. Only in longer than in marsupials and rodents measured by us but some contemporary mammals a small slip of fl.digitorum shorter than in Gobieonodon (if the latter was correctly re tibialis originates outside m. popliteus. Such a slip probably constructed by Jenkins & Schaff19 88); it is, however, nota also existed in Nemegtbaatar. In Kryptobaatarthis part of the bly wider than in measured extant mammals (unknown in tibia is poorly preserved. In contemporary mammals the Gobieonodon) . tendon of fl. digitorum fibularis passes medial to the calca neum and then divides into the fivetendons for five ungual phalanges. Flexor digitorum tibialis merges with the com mon tendon of the fl. digitorum fibularis or passes towards Hyoid apparatus the internal surface ofthe calluses ofthe foot. In Kryptobaatar We have fo und an incomplete hyoid apparatus (previously m. tibialis posterior probably inserted on the plantar surface unknown in multituberculates) in Chulsanbaatar. Because of the cuboid. of its incompleteness (only apparent stylohyoidbones have We were unable to identify short extensors and short been preserved) it is difficult to compare it with those of flexorsin the multituberculates we studied. other mammals (Gasc 1967).
Anatomical comparisons Vertebral column Cervical vertebrae In the present chapterwe do not cite the 19th-centurypapers referring to multituberculate postcranial fragments(s ome of The atlas, previously unknown in multituberculates has been which were wrongly allocated). We refer readers to a thor found in Chulsanbaatar and Nemegtbaatar. The transverse ough review of previous descriptions of multituberculate fo ramen is absent in Monotremata and most Marsupialia postcranial material by Krause & Jenkins (1983). but occurs in extant Eutheria. Among Late Cretaceous euth erians, it is absent in Asioryetes but present, although very small, in Barunlestes (Kielan-Jaworowska 1977, 1978). The Proportions of the body transverse processes are imperforate in Chulsanbaatar. In Nemegtbaatar, there is a foramen similar in position to that As appears from our reconstructions of the skeleton and of the transverse fo ramen in Barunlestes, but smaller, possi body (Figs. 45, 61), the multituberculates differ in propor- bly toa small to transmit the arteria vertebralis, and recog- 58 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
Fig. 45. Reconstruction of skeleton of Nemegtbaatargobiensis, based in part on Kryptobaatardashzevegi and Chulsanbaatar vulgaris, in dorsal and lateral views. The manus, carpus, shoulder girdle (except for the ventrai part of the scapulocoracoid), sternum, most of the ribs, part of the thoracic vertebrae and part of the caudal vertebrae have not been preserved and are reconstructed. Scale bar 20 mm.
nized by us as a ?vaseular fo ramen. In Barunlestes, there is a relatively small, in partieular in relation to a large and heavy dis tinet suleus arteriae vertebralis extending eraniodorsally head. In multitubereulates the eervieal vertebrae are short from the anterior transverse fo ramen (Kielan-Jaworowska with relatively high arches. 1978, Pl. 2: la), whieh is not obvious in Nemegtbaatar. The There are seven eervieal vertebrae in extant mammals with transverse foramen in the multituberculate atlas was appar few exeeptions (Lessertisseur & Saban 1967a, Table I). The ently absent. number of eervieal vertebrae is not known for triconodonts The ineomplete axis has been fo und for the first time in and other Mesozoie mammals (Jenkins & Parrington 1976, multitubereulates in Nemegtbaatar and Chulsanbaatar. Lillegraven et al. 1979). In the galeosaurid cynodont Thrin Judging fromthe preserved parts, the spinous proeess (most axodon, Jenkins (1971a, p. 49) fo und that 'The determina complete in the juvenile Nemegtbaatar, Fig. 9A, C) was tion of the number [of eervieal vertebrae l is eomplieated by FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 59 the fact that Thrinaxodon, unlike most mammals, retained Cervical ribs cervical ribs, the absence of which is a primary feature of In cynodonts the cervical ribs are slender, directed latero mammalian cervical vertebrae'. Jenkins concluded, how caudally and ventrally, and do not overlap each other ever, that Thrinaxodonhad seven cervical vertebrae. In the (Kiihne 1956; Jenkins 1971a; Kemp 1980). Fragmentary Liassic tritylodontid cynodont Oligokyphus (Kiihne 1956) cervical ribs, not in articulation with the vertebrae, have been there are also seven cervical vertebrae. fo und in the Triassic morganucodontid triconodont Mega The complete cervical series associated with the firstth o zostrodon; on this basis Jenkins & Parrington (1976, Fig. 18) racic vertebrae is preserved in Nemegtbaatar (ZPAL MgM-1/ reconstructed slender and ventrally directed cervical ribs in a 82) and (without thoracic vertebrae) in an unidentified Triassic triconodont. In modern mammals cervical ribs oc taeniolabidoid (ZPAL MgM-1/165, Kielan-Jaworowska cur in monotremes (on C2-C7 in Ornithorhynchus and 1989). In addition, two specimens of Chulsanbaatarpreserve Tachyglossus and on the axis in Zaglossus) and on the axis in the damaged cervicals. In most mammals the seventh verte one marsupial (Perameles), while freeribs may occur rarely bra differs fromthe preceding ones in lacking the transverse on C7 or even more anterior cervicals in a few eutherians foramen (e.g., Lessertisseur & Saban 1967a; Getty 1975; (Lessertisseur & Saban 1967a). Cervical ribs are wide, Evans & Christensen 1979). In Nemegtbaatar, although the rounded at the ends, and overlap each other in Ornithorhyn complete transverse processes on C7 have not been pre chus; they are more pointed in Tachyglossus. served, the groove between the broken ventral and dorsal We have found damaged cervical ribs on C2 and C4 in branches of the process indicates the presence of a transverse Nemegtbaatar and on C2 (uncertain), C5 and possibly also fo ramen. In an unidentified taeniolabidoid (Kielan-Jawo C7 in Chulsanbaatar (Figs. 9, 20B). In these taxa they are rowska 1989, Text-fig. l, PIs. IS, 16:1) the transverse process relatively large and roughly oval in lateral view. Multitu on C7 is long and perforated by a transverse canal, rather berculate cervical ribs are reminiscent of those of mono than reduced to a single-pronged process. The caudal costal tremes, rather than those of cynodonts and triconodonts. In fovea that occurs on C7 in many mammals is not obvious in a taeniolabidoid fam., gen. et sp. indet. (Kielan-Jaworowska Nemegtbaatarbutis preserved in the unidentifiedtaeniolabi 1989, PIs. IS, 16:1), which possibly belonged to an old doid noted above. This and the broken-offheads of the first individual, the transverse processes are very long and ribs cemented to the cranial costal foveae of Tl in Nemegt pointed, and the ribs are not discernible. It is possible that the baatar (Fig. 9A-C) demonstrate that there were seven cervi cervical ribs were present in young individuals of this taxon cal vertebrae in multituberculates, as in most mammals. and became fusedto the transverse processes in old individu Jenkins & Parrington (1976) do not mention the transverse als, as we observed in Tachyglossus. We conclude that cervical fo ramina on the cervical vertebrae in a triconodont Mega ribs were characteristic of at least some multituberculate zostrodon, although the fo ramen appears to be present (Fig. taxa. 6b of their paper), at least on C5. The transverse foramen on C7, characteristic of multitu berculates, occurs in Tachyglossus, where it is smaller than on Thoracic vertebrae, ribs and sternum the sixth vertebra. It is rarely present in extant eutherian The number of thoracic vertebrae and ribs is not known in mammals. In Lepus, fo r example, the transverse process, multituberculates. On the basis of the damaged vertebral situated opposite the anteriormost part of the body, is column in Chulsanbaatar (Fig. 18) we estimate that there pierced by a transverse fo ramen (personal observations); were 13 thoracic vertebrae in this genus. Several broken ribs such a fo ramen occurs also in Homo (Davies & Davies 1962). preserved in Nemegtbaatar and Chulsanbaatar do not allow The caudal costal fovea on C7 is, in Lepus, very small, and the an estimation of their number. firstrib articulates mostly with the cranial fovea of Tl, as is The manubrium of the sternum and one sternebra have characteristic also of Nemegtbaatar. However, the shape of been preserved only in an unidentifiedtaeniolabidoid ZPAL the body of C7 differsin multituberculates fromthat in Lepus MgM-I/165 (Kielan-Jaworowska 1989). This specimens and most extant small eutherian mammals. In Lepus the shows that multituberculates had ossifiedsternebrae. body of C7 differs from C6 in having a trapezoidal shape (ventral view), while C6 is rectangular with prominent infe Lumbar vertebrae rior (ventral) lamellae (Howell 1926). In multituberculates the difference between the shape of C6 and C7 is less dra The number of lumbar vertebrae in multituberculates is matic, as the inferior lamella (for the origin of m. longus uncertain. Krause & Jenkins (1983) stated that in Ptilodus at capitis and longus atlantis and insertion of m. longus colli) is least seven, but possibly eight, lumbar vertebrae are present. not developed on C6 and both vertebrae have a roughly We tentatively conclude that there were seven lumbar verte trapezoidal shape in Nemegtbaatar;they are more rectangu brae in multituberculates, on the basis of a poorly preserved lar in the unidentified taeniolabidoid (Kielan-Jaworowska specimen of Chulsanbaatar(Fig. 18), although the diaphrag 1989). matical vertebra cannot be recognized with any certainty. 60 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
The multituberculate lumbars differ fromthose of modem Pectoral girdle and forelimb therians, monotremes and some cynodonts (but not of the tritylodontids) in lacking the anapophyses (Jenkins 1970b; Scapulocoracoid, interclavicle and clavicle Sues 1985). They also differ from those in all extant mam All described multituberculate scapulocoracoids (Simpson mals in having poorly developed metapophyses that are not 1928; McKenna 1961; Clemens & Kielan-Jaworowska 1979; well separated from the prezygapophyses. We have fo und Jenkins & Weijs 1979; Krause & Jenkins 1983) are incom very long transverse and spinous processes of the lumbar plete. The multituberculate scapulocoracoid has been, until vertebrae in Asian multituberculates (Table 2); it is not recently, considered to be narrow, have a trough-like infra known whether similarly long processes were characteristic spinous fossa and a laterally retlectedcranial border, and lack of all multituberculates. a supraspinous fossa. It appears fromthe fragmentaryscapu locoracoids preserved in Kryptobaatar and Nemegtbaatar that the infraspinousfo ssa widens dorsally rather than being Sacrum trough-like. Clemens & Kielan-Jaworowska (1979, p. 117) pointed out that the supraspinous fossa 'is absent during part The number of sacral vertebrae in mammals varies consider of the embryological development of therians. For example, ably. There are two sacrals in monotremes and marsupials the foetus of Didelphis possesses only an infraspinous fo ssa (but only one in Perameles), most commonly three in eu until it reaches 7.5 mm in crown-rump length (Cheng, therian mammals, but for example fo ur to fivein domestic 1955)'. Jenkins & Weijs (1979, p. 407) stated with respect to mammaIs, nine in most recent xenarthrans and as many as the multituberculate scapulocoracoid: 'The laterally re 17 in glyptodonts (Lessertisseur & Saban 1967a; Getty19 75; tlectedanterior border lies above the middle of the glenoid, Starck 1979). and thus the musculature arising fromthe anterior aspect of Granger & Simpson (1929) mentioned a crushed frag the border (presumably homologous with the supraspi ment of a sacrum of the taeniolabidoid ?Eucosmodon, con natus) passed directly ventrad to the greater tuberosity.' We sisting of at least two fused vertebrae. Krause & Jenkins recognize, however, in Kryptobaatar and Nemegtbaatar the (1983) stated that there are fo ur sacral vertebrae in the narrow fossa lying to the rear of the cranial (anterior) border ptilodontoid Ptilodus kummae. In the material studied by as an incipient supraspinous fossa (Figs. 5, 12, 131, 28C). us, incomplete sacra are preserved in seven specimens Such an incipient supraspinous fo ssa is also apparently belonging to Kryptobaatar, Chulsanbaatar, Nemegtbaatar, present in front of thespine in an unidentifiedmultitubercu Sloanbaatar and Kamptobaatar (the latter poorly preserved late scapulocoracoid fromthe Lance Formation, figuredby and not described here). We support the conclusion of McKenna (1961, Fig. 3). The scapulocoracoid ofNemegtbaa Krause & Jenkins (1983) that the multituberculate sacrum tar shows that the cranial border is developed ventrally as a consisted of fo ur fusedvertebrae. In all of the studied genera prominent keel and is more retlected late rally than previ the sacrum is long, and the second sacral vertebra is longer ously known. than the firstone. The supraspinous fo ssa does not occur in monotrernes The firsttwo sacral vertebrae articulate with the ilium in (Gregory & Camp 1918), nor in Liassic triconodonts (Jen Kryptobaatar and in Chulsanbaatar, but this is not known in kins & Parrington 1976). It has been fo und, however, by Nemegtbaatar. Because of the elongation ofS2, the iliosacral Jenkins & Schaff(19 88) in a scapula attributed to the Early contact in Kryptobaataris relativelyvery long. This contact is, Cretaceous triconodont Gobiconodon, where it is very large at least in Kryptobaatar, more dorsoventral than medio (similar to that of therians). Gregory & Camp (1918) de lateral, and in the latter genus the sacrum appears to be more scribed an incipient supraspinous fossa in Cynognathus (see firmly synostosed with the ilia than in Chulsanbaatar and Jenkins 1971a, fo r a review of literature on the shoulder Nemegtbaatar. girdle in cynodonts). Kiihne (1956) does not mention its presence in the advanced tritylodontid Oligokyphus, in which the scapular part of the scapulocoracoid is narrow, as Caudal vertebrae in multituberculates, while the coracoid part is very exten sive. It seems to us that the narrow fo ssa reconstructed by We have fo und three anterior caudal vertebrae in Kryptobaa Kiihne (1956, Fig. 52B) on the right side ofthe cranial view of tar and two isolated caudals in Catopsbaatar. Caudal verte the scapulocoracoid, might correspond to an incipient sup brae in Nemegtbaatar have not been preserved, but on the raspinous fossa. basis of distinct scars fo r the origin of m. sacrocaudalis The multituberculate coracoid is developed as a small dorsalis (Fig. 36B) on the last fo ur lumbar vertebrae (dam pro cess on the ventral angle of the scapula and is not bent aged on anterior lumbars), we conclude that the tail was mediallyas in therian mammals. The ventral surface of the possibly longer than the rest of the body in Nemegtbaatar. coracoid prolongs the longitudinal diameter of the glenoid FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 61 fossa and thus reduced the flexor-extensor mobility of the humeral joint. We should make it clear that in animals with abducted limbs, flexion-extensionof the fo relimb does not correspond to protraction-retraction as in mammals with parasagittal limbs (referred to further as 'parasagittal'; see 'Functional anatomy') but is more complicated, as at the same time abduction-adduction takes place. In multituber culates there is no supraglenoidtubercle characteristic of the Theria (Fig. 28). The multituberculate acromion described herein is peg-like and 'embraces' the humeral head cranio laterally. One can visualize a clavicle abutting against it as reconstructed by Jenkins & Weijs (1979, Fig. 12c) but situ ated lower than in their reconstruction, in a position rather similar to that in Didelphis (Jenkins & Weijs 1979, Fig. 12d). We reconstruct the multituberculate scapulocoracoid as leaning backwards as in therian mammals (Fig. 45). Until recently the multituberculate interclavicle and clavicle were not known with certainty (see Krause & Jenkins D 1983, fo r review). Sereno & McKenna (1990) reported the Fig. 46. Diagram illustrating proximal views of left humeri and degree of twisting in rnultituberculates (A, Bl, eutherians (Cl and marsupials (Dl. presence of these elements in a multituberculate from the The greater tubercle is to the right. DA-B. ?Lambdopsalis bulla, lVPP Late Cretaceous of Mongolia, but the material has yet to be V90S l and lVPP V8408, respectively. DC Rattus norvegicus ZIN 83. OD. described. We have not found interclavicles and clavicles in Marmosa sp., ZIN 1110. To establish the angle oftwisting, the hurneruswas the material studied. placed vertically, and its distal axis, across the epicondyles (a), correspond ing to the axisof the flexor-extensorsin the ulnar joint, was drawn with the carneralucida. Then on the same drawing the humeraI head and the line across the proximal end of the hurnerus, between the middle of the Humerus intertubercular groove and the rniddleof the caudal margin of the hurneral Numerous incomplete multituberculate humeri have been head (bl, were drawn. The perpendicular to the latter line (cl corresponds to the flexor-extensorexcursion in the shoulder joint; the angle of twisting described or figured by Gidley (1909), Simpson (1928a), lies between it and the axis ofthe flexor-extensorsof the distal end. In C and Deischl (1964), Sahni (1972), Jenkins (1973), Kielan-Jawo D the lines a and c are subparallel, and there is almost no twisting. Scale bars rowska & Dashzeveg (1978), Krause & Jenkins (1983), Srnm. Kielan-Jaworowska (1989) and Bleefeid (1992); two COill plete multituberculate humeri (both broken and glued to gether) were described by Kielan -J aworowska & Qi (1990). The multituberculate humerus is characterized by a spheri culates, the reconstruction of the Tugrigbaatar humerus cal head, the lesser tubercle only slightly smaller than the should be corrected. greater one, wide intertubercular gro ove, teres tuberosity Two right humeri of? Lambdopsalis bulla allow us to estab crescent-shaped; posterior crest, extending in dorsal aspect lish the degree of relative twisting of the proximal and distal from the head to ectepicondylar flange; a robust and wide ends fo rthis genus (Fig. 46; see also Simpson 1928b, Fig. 52). distal end, with very convex radial and ulnar condyles, ent In small therian mammals measured by us the angle of epicondylar fo ramen and a strong degree of twisting. The twisting is about 5°, in Tachyglossus aculeatus 45° and in multituberculate humerus is reminiscent ofthat in primitive Eozostrodon about 50° (Jenkins & Parrington 1976). In triconodonts in having aImost subequal greater and lesser ? Lambdopsalis IVPP V8408 it is 38° while in IVPP V9051 it is tubercles, a crescent -shaped teres tuberosity and wide distal 24°; this difference is apparently due to inaccuracy in gluing end (Jenkins & Parrington 1976). These characters occur the parts ofboth humeri. It seems to us that IVPP V8408 is also in cynodonts (Jenkins 1971a) and monotremes (per closer to the natural condition and that the angle was about sonal observations); in both these groups, however, the lesser 33-35°. The intertubercular groove is very wide in multi and greater tubercles are less clearly defined,and the humeri tuberculates; it is 32% of the width of the proximal epiphysis are more robust than in multituberculates. in Nemegtbaatar and 28-3 1% in ?Lambdopsalis, while in Kielan-Jaworowska & Dashzeveg (1978) possibly over small modem rodents it is only 14-23%. estimated the length of the humerus in Tugrigbaatar and underestimated the width of the distal part. The humeri of Radius and ulna ?Lambdopsalis (Kielan-Jaworowska & Qi 1990) and those of the North American multituberculates belonging to Ptilo Proximal parts of multituberculate ulnae have been de dontoidea and Taeniolabidoidea (Krause & Jenkins 1983) scribed by Jenkins (1973) and incomplete radii and ulnae by have an expanded distal end. If this holds fo r all multituber- Jenkins & Krause (1983). The proximal part of the leftradius, 62 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994) preserved together with an almost eomplete ulna (with a and ? Mesodma that cloesnot open to the pelvieeavity. In the broken oleeranon) in Nemegtbaatar (ZPAL MgM-I/81), is fo ur taeniolabidoid genera deseribed or discussed here the most eomplete multitubereulate fo rearm known so far (Kryp tobaatar, Chulsanbaatar, Sloanbaatarand Kamptobaa (Fig. 14A). The distal end of our ulna, although damaged, tar) the pelvis is narrowwith a keel-like isehiopubie symphy resembles that in small therian mammals and strongly differs sis, and a postobturator noteh (or foramen) was possibly fr om that in Tachyglossus. Therefore we suggest that the present within the symphysis, at least in Kryptobaatar rotation between the distal parts of radius and ulna in multi (Fig. 2). The only pubis of Nemegtbaatar (Fig. 16F) has been tubereulates was around the styloid proeess, as in primitive distorted, and the ventral keel has not been preserved. As, therian mammals (Lewis 1989). Krause & Jenkins (1983) however, the keel oeeurs in all the genera belonging to both deseribed the multitubereulate radius as mediolaterally the Ptilodontoidea and Taeniolabidoidea in whieh this compressed. The proximal and distal parts of the radii pre region is known, we assurnethat it oeeurred also in Nemegt served in Nemegtbaatar are eranioeaudally compressed. baatarand was eharaeteristie of Cimolodonta and possibly is a multitubereulate autapomorphy. Manus The multitubereulate pelvis differsfrom those of therian mammals in being deeper. This is related to the abdueted Anineomplete manus of Ptilodus was deseribed by Krause & position ofthe multitubereulate hind limbs and the origin of Jenkins (1983). In this paper we deseribe four tentatively femoral adduetors ventraI to the aeetabulum, rather than identified carpal bones of Nemegtbaatar. These, together eaudal, as in therian mammals (see 'Funetional anatomy' with the material deseribed by Krause & Jenkins, show that and Figs. 48, 49). A deep pelvis is also eharaeteristie of there were three bones in a proximal row in the multituber monotrernes (Gregory & Camp 1918; Jouffroy& Lessertis eulate carpus and five (including the praepollex) in a distal seur 1971), but the multitubereulate pelvis differs greatly row, but the centrale has not been found as yet. As the manus fromthat of monotrernesin having a very narrow isehial are; has not been preserved in multitubereulates studied by us, its whereas in monotrernes, in relation to oviparity, the isehial reeonstruetion in Fig. 45 is entirely tentative. are is widely open, U -shaped. In multituberculates the iliosaeral angle is very large in comparison to that in extant therian mammals (Fig. 37B2, Dl Pelvie girdle and hind limb and Table 1). In extant mammals with 'parasagittal' hind limbs (see 'Funetional anatomy') the iliosaeral angle varies Pelvis with the body mass of the animal (Lessertisseur 1967). In
An incomplete pelvis of Ptilodus was deseribed by Gidley (1909), who suggested that multitubereulates probably had marsupial (epipubie) bones. Kielan-Jaworowska (1969) Table 1. Iliosaeral angle in multituberculates and extant mammaIs. fo und multitubereulate epipubie bones in Kryptobaatar(s ee also Fig. 2 in this paper). Cato No. Speeies Ang Hab Granger & Simpson ( 1929) deseribed an ineomplete pelvis 81 Nemegtbaatar gobiensis 33° of ?Eucosmodon and stated that it differs from those of 85 Chulsanbaatar vulgaris 37° therian mammals in having the aeetabulum open dorsally 41 Kryptobaatar dashzevegi 36° and the ischia meeting eaeh other at an aeute angle. An open * Ornithorhynchus anatinus 40° aq 31024 Tachyglossus aculeatus 38° f, t aeetabulum is eharaeteristie also oftrieonodonts (Jenkins & 13951 Antechinus stuarti 17° Parrington 1976), the tritylodontid Oligokyphus (Kiihne 1I10 Marmosa sp. 1I0 1956) and some arboreal (gliding) marsupials (Elftman 192 Neomys fo diens 9° aq, t 1929), while in monotrernesit is only partly eovered dorsally 1380 Elephantulus rozeti 16° 800 Sciurus persicus 19° (see 'Funetional anatomy' for interpretation). 175 Citel/us fu lvus 18° Deisehl (1964) deseribed several incomplete multituber 206 Citel/us xanthoprymnus 9° eulate pelves. Kielan-Jaworowska (1969, 1979) demon 59 Spermophylopsis leptodactylus 14° strated that in Kryptobaatar the isehial are is very small, 215 Dryomys nitedula 15° 221 Glis glis 14° limited only to the dorsal part of the ischia, the isehial tuber 83 Rattus norvegicus 16° is developed as a parabolie proeess, strongly protruding 314 Mesocricetus brandti 10° dorsally, and parts of the pubes and ischia are firmly fused 311 Cricetulus migratorius 9° ventrally to form a keel. Krause & Jenkins (1983) fo und the 428 Meriones tamariscinus 13° lI7 Allactaga jaculus 19° keel of the isehiopubie symphysis in North Arnerieangenera belonging to both the Taeniolabidoidea and Ptilodontoidea. Cat. No. (eatalogue numbers) refer to ZPAL MgM-I/ colleetion for the They also noted the presenee of a postobturator fo ramen firstthree taxa; the remainder to ZIN, Laboratory ofMammals colleetion. Ang = angle; Hab = habits; aq = aquatie; f = fossorial; r = ricoehetal; t = within the isehiopubie symphysis in Ptilodus, ?Eucosmodon terrestrial; s = seansorial; * = after Lessertisseur 1967. FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 63 small mammals this angle ranges from9° to 19°. In multitu head. The morphology of the femora of therian mammals is berculates this angle is 35-37° (measured by the method of diverse, but in general the head is placed on a well-developed Huxley 1879, rather than Le Damany 1906, because of the neck and projects craniomedially as in multituberculates. lack of complete skeletons; see also Lessertisseur 1967 and The greater trochanter, which is very prominent in multitu Fig. 37B2 and Dl herein). This angle in multituberculates is of berculates, is variably developed in therians, usually lower roughly the same value as in Tachyglossus (38°), while in than, or as high as the head (Greene 1935; Lessertisseur & Ornithorhynchus it is 40°. A large iliosacral angle in mono Saban 1967b; Getty 1975; Starck 1979; and personal observa trernes and multituberculates is possibly a plesiomorphic tions). The lesser trochanter in multituberculates as charac fe ature. terized above is very different from that in therians. The Jenkins & Schaff (1988) reconstructed the pelvis of the subtrochanteric tuberde characteristic of multituberculates Cretaceous triconodont Gobiconodon (in which the ventral does not occur in other mammals, to our knowledge. The part has not been preserved) as very shallow, similar to that of function of this tuberde is not dear to us. Simpson & Elft therians. As the hind limbs in Gobiconodon were abducted, man (1928) regarded it as the insertion of ill. iliocapsularis we speculate that the triconodont pelvis was possibly deeper, (which they regarded as a synonym of iliofemoralis). How similar to that of multituberculates, and the iliosacral angle ever, iliocapsularis is a synonym of capsularis, and iliofemo larger. ralis of reptiles is homologous to gluteus (Romer & Parsons 1986). As m. capsularis in modem mammals inserts more Femur medially, dose to the lesser trochanter, it seems more prob able that the discussed tuberde corresponds to the insertion The femur is the stoutest bone in the multituberculate skel oflig. iliofemoralis. eton, and several fragmentaryand complete femora belong ing to differentgenera are known (Gidley 1909; DeischI 1964; Tibia, fibulaand parafibula Simpson & Elftman19 28; Granger & Simpson 1929; Sloan & Van Valen 1965; Krause &Jenkins 1983; and this paper). The Fragmentary or complete tibiae, belonging to several ptilo multituberculate femur is characterized by a head with an dontoid and taeniolabidoid genera, are known (Gidley 1909; extensive articular surface and a long neck forming an angle Granger & Simpson 1929; Deischl 1964; Krause & Jenkins of 50-60° to the shaft; a prominent greater trochanter ex 1983). For a long time the fibulaewere incompletely known, tending beyond the head; a prominent plate-like lesser tro and the first complete one (belonging to Ptilodus) was de chanter, convex lateroproximally and concave medio scribed by Krause & Jenkins (1983). We described above distally, stronglyprotruding ventrally and placed at the point tibiae and fibulaepreserved together in Kryptobaatar, Nem of confluence of the greater trochanter with the neck; ab egtbaatar and Chulsanbaatar. sence of the third trochanter; in dorsal aspect a distinct In mammals with 'parasagittal' (see 'Functional anato subtrochanteric tuberde (see 'Terminology'); small distal my') limbs, the craniocaudal diameter of the tibia is much condyles; and a shallow trochlea. greater than the mediolateral (Kummer 1959a, 1959b; Soko The trochanteric (digital) fossa has been described by lov et al. 1974). In multituberculates, in contrast, the medio Simpson & Elftman (1928) and Krause & Jenkins (1983) as lateral diameter is relatively large in respect to the cranio divided into a proximal part situated between the two tro caudal, which is possibly related to the fact that because ofthe chanters and a distal part, fissure-like in shape, placed lateral abducted position of their limbs, the stress on the tibia to the lesser trochanter. Granger & Simpson (1929, p. 641) during the propulsive phase is directed medially. In Krypto stated: 'Lateral to the lesser trochanter and between it and the baatar (ZPAL MgM-I/4l) the craniocaudal diameter of the gluteal crest is another equally definite and larger [than the tibia is 54% of the mediolateral diameter, in Nemegtbaatar digital fo ssa l elongated fo ssa which do es not have any certain (ZPAL MgM-IJ110) 60% and in ?Eucosmodon 63% in the separate homologue on any other femur compared by us.' proximal part and 65% in the distal part. In modem therian We believe that the latter fo ssa is not related to the trochan mammals these values are 81% in Marmosa sp. (ZIN 1110), teric fo ssa and we designate it (see 'Terminology') the post 107% in Elephantulus rozeti (ZIN 1380) and 105-150% in trochanteric fo ssa. different species of rodents cited in Table 2. The multituberculate femur is very different fromthat of The multituberculate tibia is characterized by a markedly monotrernes,triconodonts and docodonts (Vialleton 1924; asymmetrical proximal end, with a small medial and a large Parrington 1961; Jenkins & Parrington 1976; Jenkins & lateral facet. The prominent, hook-like triangular process Schaff 1988; Henkel & Krusat 1980; Krusat 1991), in which overhangs the shaftlaterally and bears a facet for the fibula. the femoral neck is short and wide, the greater trochanter Deischl (1964) noted that the distal end of multituberculate does not extend beyond the head, and both trochanters are tibia is similar to that of Didelphis, where there is a very triangular. These trochanters are verydifferent in shape and prominent medial malleolus and a large, relatively flatlateral position from those in multituberculates and arise sym condyle. We observed similar structure in other marsupials, metrically (in ventral and dorsal views) on both sides of the induding Antechinus stuarti (Dasyuridae), Trichosurus vul- 64 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994) pecula and Phalanger maculeatus (Phalangeridae), as well as Pes in Kryptobaatar, Nemegtbaatar and an unidentified multi Isolated bones of multituberculate pedes were described or tubereulate from the Hell Creek Formation (Fig. 55A). In figured by Gidley (1909), Simpson (1928a), Granger & ?Eucosmodon the distal end of the tibia differsfrom that of Simpson (1929), Deischl (1964), Sahni (1972), Bleefeld Asian multituberculates and froma tibia fromthe Hell Creek (1992) and Szalay (1993). Granger &Simpson (1929) recon Formation in having a small, flatmedial condyle developed structed the multituberculate pes (of? Eucosmodon sp.) with in addition to the medial malleolus (Fig. 56F). Krause & the longitudinal axis extending along the third ray of the fo ot Jenkins (1983, Fig. 22) referred to the medial malleolus in the (we follow Leonardi 1987 in definingthe position of the pes tibia of? Eucosmodon as the medial tibial condyle. This nota afterthe position of the third ray of the foot - Mt III and D tion may be justified as, in fact, on the cranial and caudal Ill). They also demonstrated that the cuboid facet in the sides of the medial malleolus there are articular surfaces fo r multituberculate calcaneum is arranged obliquely medio the astragalus (see 'Functional anatomy'). distally, rather than distally as in all other mammals, and The fibular head bears on its lateral part a hook-like reconstructed the calcaneum not supported distally by any triangular proeess for articulation with the above-men bone. Krause & Jenkins (1983) and Jenkins & Krause (1983) tioned hook-like proeess on the tibia. In lateral view these described a nearly complete pes ofPtilodus and discussed its proeesses are aligned. The fibular shaft appears relatively function. They argued that the multituberculate femora more robust (with respect to that of the tibia) in Nemegtbaa were not parasagittal, with which we agree. aur reconstruc tar and Chulsanbaatar, than in Kryptobaatar. Although the tions (Figs. 54 and 57) differ from those of Granger & fibula in Ptilodus has been preserved in an articulated skel Simpson (1929, Fig. 29), Krause & Jenkins (1983, Fig. 24) eton, Krause & Jenkins (1983) were not able to establish its and Szalay (1993, Fig. 9.10) in that we place Mt III at an angle orientation with certainty. The speeimens described here of 30° in respect to the longitudinal axis of the tuber calcanei. show that the fibulain multituberculates does not participate In our reconstruction Mt V articulates with the distal margin in the knee joint and is situated caudal to the tibia in the of the calcaneum medial to the peroneal groove (see 'Func proximal part, but lateral in the distal part. tional anatomy'). In the Triassic triconodont Erythrotheriumthe fibulapar Multituberculate calcaneum differs fromthat ofthe Lias ticipates in the knee joint and is placed lateral to the tibia, sic triconodonts Oenkins & Parrington 1976) in having a arranged obliquely craniodorsally to ventrocaudally (Jen well-developed tuber calcanei, compressed laterally and kins & Parrington 1976). In the Early Cretaceous tricono similar to that in therians. However, Jenkins & Schaff(19 88, dont Gobiconodon the exact position of the fibulain relation Fig.1) reconstructed the calcaneum of the Early Cretaceous to the tibia is not known, but Jenkins & Schaff(19 88, Fig. l) triconodont Gobiconodon with a tuber calcanei similar to reconstructed it subparallel and lateral (slightly laterocau that in therians. dal) to the tibia. In monotremes the large fibula is very At least two types of multituberculate calcanea may be different from that in multituberculates, and it is placed recognized. In one type, represented by Asian calcanea de entirely lateral to the tibia (Haines 1942). The respective sizes scribed here, an unidentified multituberculate calcaneum of tibia and fibulain extant therian mammals vary (Lessertis fromthe Hell Creek Formation (Fig. 55E-G) and an uniden seur & Saban 1 967b). As demonstrated by Barnett & Napier tified Late Cretaceous ptilodontoid calcaneum figured by (l953b), in marsupials (but not in the Peramelidae) there is Szalay (1993, Fig. 9.8), the peroneal gro ove is wide and the generally some degree of femorofibular contact, which is peroneal tubercle is directed laterodistally. In the other type, absent in Eutheria (Barnett & N apier 1953a). In both groups, represented by an unidentified multituberculate from the however, irrespective of the differences in the size of the Lance Formation (Fig. 55H, I) and ? Eucosmodon sp. (Fig. fibula, this bone is placed more laterally with respect to the 56H-J) , the peroneal groove is narrow and the peroneal tibia than in multituberculates. tubercle directed more distally. However, in both types the Krause & Jenkins (1983) described the firstmultitubercu peroneal groove is very deep and the peroneal tubercle is late parafibulae, found in association (but not in articula clearly set offfrom the calcaneal body; in this respect the tion) with the hind limbs of Ptilodus. We have found the multituberculate calcaneum differs from those of other parafibulae in articulation, although slightly displaced, in mammals. Kryptobaatarand Chulsanbaatar and an apparent fragment If our reconstruction of the multituberculate pes is cor of the parafibulain Nemegtbaatar (Figs. 2B, 3A, B, 17F, H, I, rect, multituberculates would differ from all mammals in 24B, C). It seems probable that the presenee of this ossicle having Mt V articulating with the calcaneum. Among extant was characteristic of multituberculates as a whole. As argued reptiles Mt V articulates with the calcaneum (fused to the under 'Myological reconstructions' (Fig. 44A), m. gastro astragalus) only in Sphenodon (Romer & Parsons 1986). cnemius lateralis possibly originated in multituberculates Calcaneo-Mt V contact occurs in various extinct tetrapods, from the parafibula (as in some marsupials), rather than e.g., in a few therapsids (gorgonopsians, dinocephalians and fromthe femur as in eutherians. dicynodonts); it has also been found in a primitive archo- FOSSILS ANDSTRATA 36 (1994) Anatomy and habits of multituberculates 65
sauromorph, some lizards, an early rhynchosaur and some the 'astragalar head', rather than being situated on its distal theeodonts (Romer 1956; Bonaparte 1971; Cruickshank end as in therians. 1972; Carroll 1976, 1988; Chatterjee 1978). It follows that multituberculates 'solved' the movements In pelycosaurs the fifthtarsal is situated between the calca in the astragalonavicular joint differentlythan therians and neum and Mt V. In bauriamorphs, cynodonts and most monotrernes: there is abduction-adduction in a horizontal therapsids (see, e.g., Schaeffer 1941a, 1941b; Jenkins 1971a; plane, around a vertical axis, in multituberculates; prona Szalay 1993), there is a gap between the calcaneum and Mt V, tion-supination (rotation around longitudinal axis) in which, as demonstrated by Schaeffer (1941a) on the roent therians; and flexion-extension in dorsopiantar direction, genogram of Bauria pes, is not an artefact. Schaeffer argued around a transversal axis, in monotrernes(per sonal observa that this gap may be filled either with a lateral fibrocarti tions by PPG). The movements in the astragalonavicular laginous extension fromthe cuboid, or by apersistent, carti joint in other mammals still need to be explored. laginous fifthtarsal. Schaeffer (1941b, p. 5) stated: 'Granger & Simpson (1929) have recorded the presenee of a large gap in the same position in the multituberculate Eucosmodon, although in this case the fifthmetatarsal does not articulate with the extreme lateral border of the cuboid. This gap Functional anatomy certainly was not filled by a cartilaginous fifth tarsale.' As argued above, we believe that this gap does not exist in Reconstruction of locomotion multituberculates. Introductory remarks In the Middle Triassic Manda cynodont examined by Jenkins (1971a) and Szalay (1993), there is a large gap be It was generaUy accepted afterthe analysis of the functionof tween the calcaneum and Mt V, and the calcaneo-cuboid the multituberculate pes by Krause & Jenkins (1983) and facet is distal rather than mediodistal. One can visualize that Jenkins & Krause (1983) that at least some multituberculates during the evolution leading fromtherapsids to multituber were arboreal in their habits. Rowe & Greenwald (1987, p. culates, when the fifth tarsal disappeared, the calcaneum 25A) went further and stated: 'It now appears more likely came into contact with Mt V. At the same time the cuboid that arboreality was the ancestral habit ofTheriiformes [the facet on the calcaneum shiftedfrom nearly distal to medio taxon comprising the immediate common ancestor ofMul distal position. The calcaneo-Mt V contact and mediodistal tituberculata and Theria and aU its descendants l and that the cuboid facet on the calcaneum are multituberculate autapo origin of Multituberculata involved dietary specialization morphies. In the evolution leading to therian mammais, within that niche.' We do not see any reason to presume that when the fifthtarsal disappeared, the cuboid extended later arboreality was primitive for multituberculates. We shaU aUy, supporting the distal end of the calcaneum, and the argue below that the Late Cretaceous Asian multitubercu cuboid facet acquired a distal position. lates studied by us were possibly terrestrial runners. For this In the Mongolian taxa studied by us, the plantar side of reason the discussion on the reconstruction oftheir locomo the astragalus is poorly exposed, and we have not described tion begins with a recapitulation of terrestrial gaits. the astragalar canal. Szalay (1993, p. 121) stated: 'The In symmetrical gaits a movement of one fo relimb is fol unique and arched buttress around the astragalar canal (ac) lowed by the movement of either of the hind limbs, after of multis requires an eventual explanation - it is highly which the next fo relimb and the next hind limb move; at the diagnostic.' Granger & Simpson (1929), referring to the same time the lateral flexures of the body take place. As a proeess on the astragalus for articulation with the navicu result the pattern oflimb movements on the right side of the lar, stated (p. 644): 'The latter proeess is, of course, homol body is a mirror image of those on the left. In asymmetrical ogous with the head of normal primitive therian astragalus, gaits the fo relimbs move firstand then the hind limbs. There but here it has no neck and is not cut offfrom the main is no symmetry of movements between the right and left body of the bone.' This proeess has also been referred to by sides of the body, no lateral flexures,and the extension and Krause & Jenkins (1983) as the astragalar head. We do not flexion of the vertebral column occur in a sagittal plane fo llow this usage for the following reasons. Szalay (1993, p. (Howell 1944; Sukhanov 1974; Gambaryan 1967, 1974). 121) pointed out that: 'The articulation of the astragalus Amphibians, most extant reptiles, and monotrerneshave a with the navicular is ... diagnostic [for multituberculatesl, sprawling limb posture, and the proximal segments of their as it is an extreme and decidedly unique modificationof the limbs, when seen in caudal and cranial views, are arranged at primitive mammalian trait of a convex, or sellar navicular about 90° to the parasagittal (vertical) plane. We refer to the AN facet.' We agree with Szalay and argue that the astrag sprawled limbs as abducted. The angle under which the alonavicular articulation worked in multituberculates dif abducted limbs are positioned may be much smaUer than ferently than in therians and aU other mammais. In multi 90°. With limbs arranged at 90°, the humerus and femur tuberculates the facet for the navicular is saddle-shaped, show their full lengths in dorsal view, and if the angle is extending along the dorsal and medial sides of the base of smaUer the humerus and femur appear shorter in both dorsal 66 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994) and lateral views. The limbs of therian mammals were tradi Function of the spinous processes of the tionally referred to as parasagittal. However, as demon lumbar vertebrae strated by Jenkins (1971b), Didelphis, Tupaia, Rattus and The function of the spinous proeesses of the vertebrae in Mustela have humeri that functionat angles of 10-30° from mammalian gait has been diseussed by Slijper (1946), Brovar the parasagittal plane, while the femoral axis is positioned (1935, 1940) and Kummer, (1959a, 1959b) who demon 20-50° fromthe parasagittal plane (see also Jenkins 1974 and strated that the length of the spinous processes is related to Jenkins &Weijs 1979). Even in cursorial mammals the femur the load on the flexionand extension of the spine. In order to is slightly abducted (Jenkins & Camazine 1977). The gait of establish the relative lengths of the spinous proeesses in therians, however, differsfrom that of animals with sprawl multituberculates and in small extant therianmammals, we ing posture. In therians the distal end of the femur moves in measured the lengths of the spinous processes in relation to a parasagittal plane and during the propulsive phase no the respective lengths between the anterior margin of the adduction takes place (Jenkins &Camazine 1977, Figs. 1-3). prezygapophysis and the posterior margin of the postzyga In monotremes (Pridmore 1985), during the propulsive pophysis (Fig. 4 and Table 2). phase adduction of the femur occurs, and as we shall argue The partly broken-off spinous proeesses ofthe last lumbar below, the same apparently took place in multituberculates. vertebrae have been preserved in Nemegtbaatar (Figs. 8A, Il Because of this difference (in spite of the more or less ab and 35). In Fig. 36B2 we give two reconstructions of the ducted position of the femur in therian mammals), in the spinous processes in Nemegtbaatar, marked by dashed and discussion that follows, we conditionally accept that the dotted lines. limbs of therians move in a parasagittal plane, and we refer to In extant mammals that use asymmetrical gaits, there is a them as 'parasagittal'. correlation between the lengths of the spinous proeesses and In extant small mammals there occur three basic quadru the mass of m. erector spinae. If our first reconstruction of pedal asymmetricalgaits: primitive ricochet (e.g., Meriones), the lengths ofthe spinous proeesses in Nemegtbaatar( dashed ricochet (e.g., Allaetaga) and gallop (e.g., Lepus) (Gambar lines in Fig. 36B2 ) were true, one may conclude that the mass yan 1967, 1974). In galloping mammals there are two phases of erector spinae in Nemegtbaatarwas relatively greater than of flightin the cycle: extendedflight and gathered flight(s ee in highly specialized ricochetal mammals such as, e.g., 'Terminology'). In ricochetal and primitively ricochetal Allactaga (Table 3, Fig. 47). If our second reconstruction mammals only the extended tlight occurs. In galloping were true (dotted lines in Fig. 36B2), then the mass of the mammals (e.g., in Lepus) the angle oftake-offis smallerthan erector spinae would be smaller than in Allaetaga, but still in the primitively ricochetal and ricochetal mammals (Gam greater than in, e.g., Meriones. baryan et al. 1978).
Table 2. Ratio of the length of the transverse and spinous proeesses of the last lumbar vertebrae to the length between the pre- and postzygapophyses (in percent).
Cat. L4 L5 L6 L7 No. Speeies spi tr spi tr spi tr spi tr
81 Nemegtbaatar gobiensis, l 94 100 106 100 100 133 81 Nemegtbaatar gobiensis, 2 81 86 106 86 86 133 13951 Antechinus stuarti 60 35 62 37 62 37 63 34 1380 Elephantulus rozeti 90 62 93 102 800 Sciurus persicus 41 44 47 54 55 61 72 67 175 Citellus fu lvus 27 20 30 32 32 37 37 59 159 Citellus xanthoprymnus 26 27 28 37 30 41 35 53 59 Spermophilopsis leptodactylus 49 52 63 60 65 68 60 96 79 Glis glis 34 34 38 42 43 53 45 59 83 Raffus norvegicus 63 37 65 47 64 47 55 45 314 Mesocricetus brandti 27 22 30 28 30 37 50 48 311 Cricetulus migratorius 30 50 35 54 35 70 37 63 403 Calomyscus bailwardi 52 31 58 55 62 67 79 85 428 Meriones tamariscinus 75 87 79 97 90 110 80 III 114 Meriones meridian us 56 41 66 57 67 80 71 109 117 Allactaga jaculus 75 61 79 66 85 73 98 99 143 Lepus europaeus 70 125 73 126 74 131 70 121
Cato No. (catalogue numbers) refer to ZPAL MgM-I/ collection for Nemegtbaatar and to ZIN, . Laboratory of Mammals collectlOn for all other taxa; spi = spinous proeess; tr = transverse proeess. Two dIfferent data fm Nemegtbaatar gobiensis refer to two different reconstructions of the lengths of sp mo us proeesses m Flg. 36 B,; l = the lengths marked by dashed lines; 2 = by dotted lines. For jumping mdexes (Jumpmg dlstance to body length) see Table 5. FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 67
As a rule, the spinous processes of the lumbar vertebrae in 6.0 Nemegtbaatar gobiensisp mammals are longer than those of the caudal vertebrae. In ' Kryptobaatar the spinous process of L6 and L7 (numbers 2 5.5 AI/actaga ela ter - and 3, respectively, in Fig. 2) have been broken, while Cd1 5.0 Weighing factor (WF) = 17
(number 5) has been completely preserved. If the spinous 0 4. pro cess ofL6 was at least as long as that of Cd1, it would be 5 � 4.0 91 % of the length between the pre- and postzygapophysis, � Meriones blackleri ..c while that of L7 would be 97% of the same length. In ·�3.5 Chulsanbaatar (ZPAL MgM-I/83) these processes are not 5: well observable (Fig. 18). We measured thepreserved parts of 3.0 '" Rattus norvegicus broken L4, L5 and L7, and they correspond to 71 %, 65% and EI/obius lutescens 54%, respectively, of the length between the corresponding 2.5 pre- and postzygapophyses; this shows that even when 2.0 Mesocricetus raddei broken they are relatively longer than the corresponding 1.5 spinous processes in Meriones meridianus (Table 2). This O 10 20 3) 40 50 60 7000 100 suggests that our first (dashed lines) reconstruction of the Length ratio lengths of the spinous processes in Nemegtbaatar (Fig. 36B2) Weighing factor, WF, in small modem mammals and is more probable. Fig. 47. Nemegtbaa tar, representing a correlation between the mass of m. erector spinae and of the mean height of the two last spinous processes of the lumbar vertebrae. Numerals on abscissa (length ratio) represent mean length of spinous pro cess oftwo last lumbar vertebrae (L.) as percentage of distance between Table 3. Weight of erector spinae muscles in percent of the total weight of prezygapophysis and postzygapophysis (L,). Numerals on ordinate the skeleton and muscles, excluding hind limbs. (weight ratio) represent mass of erector spinae (Wm ) as percentage of total mass of skeleton and muscles of body (W,), excluding mass of hind limbs. Species a b c I,a+b+c = Length The weighing factor WF can be expressed as length ratio/weight ratio. In iliocos. semispi. longi. e. spinae ratio measured extant mammals WF is 17, except in Rattus norvegicus, where it
is 22. Assuming WF = 17 also for a tentative value for its Mesocricetus raddei 0.10 0.59 1.18 1.27 30.0 Nemegtbaatar, Ellobius lutescens 0.51 0.41 1.3 2.22 34.0 weight ratio is 5.7. (See also Table 3.) Meriones blackleri 0.29 0.78 2.86 3.93 68.0 Rattus norvegicus 0.21 0.43 2.11 2.75 60.5 Allactaga elater 1.09 1.06 3.25 5.40 97.0 Nemegtbaatar gobiensis 100.0 86.0 structed the origin of the pelvic muscles in Nemegtbaatar, the iliocos. = iliocostalis; semispi. = semispinalis dorsi; longi. = longissimus scars ofwhich are discemible on the verywell preserved bone dorsi; e. spinae = erector spinae. Length ratio = ratio of the average length surface (Fig. 37A), and we compare them with those of of the spinous processes ofL6 and L7 to the distance between the prezyg apophyses and postzygapophyses (in percent). Two numerals for Nemegt Meriones tamariscinus and Antechinus stuarti (Fig. 38), baatar refer to two reconstructions of the lengths of the spinous processes which are of approximately the same size as Nemegtbaatar. in Fig. 36 B" The firstnumeraI (100.0) corresponds to the dashed lines, the In these modem taxa all of the femoral adductors originate second (86.0) to the dotted lines. caudal to the vertical line extending ventrally from the acetabulum; in Nemegtbaatar they originated ventral to the acetabulum and cranial and caudal to the mentioned vertical line. The distance between the acetabulum and the ventral We found in mammals that use asymmetrical locomotion margin of the symphysis (although this is broken) is, in a correlation between the length of the spinous processes of Nemegtbaatar, much greater than in Meriones and Ant the last lumbar vertebrae and the length ofthe jump (Table 2 echinus. In Kryptobaatar, in which the ventral keel has been and Fig. 47). We define the jumping index (afterZug 1972) preserved, this distance is still relatively greater than in Nem as a ratio of the jumping distance to the body length. The egtbaatar. spinous processes of Nemegtbaatar (if the reconstruction in We also suggest that the ventral keel of the multitubercu dashed lines were true) would be relatively longer than in all late pelvis, a feature not found in other mammals, developed the taxa cited in Table 2, which indicates the capability fo r as a response to the origin of femoral adductors ventral to the strong extension and flexion of the vertebral column in a acetabulum. The fenestration of the keel (postobturator sagittal plane and long asymmetrical jumps. fo ramen or notch) is possibly related to muscular attach ments, as speculated by Krause & Jenkins (1983). In order to understand how the hip joint worked in the pelvie muscles Function of multituberculates, we compared it with that of Rattusnor For the analysis of the locomotion it is important to recon vegicus, the running mechanism of which has been studied struct the topography of the pelvic muscles. We recon- by cinematography (Kuznetsov 1983). The configurationof 68 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
Fig. 48. Diagram illustrating position of fe moral adductors and gluteus medius during the propulsive phase in caudal view. Dashed lines denote horizontal plane. DA. Eutherian mammal exemplified byRattus Cp arasagittal' limbs). DB. Multituberculate, exemplified by Nemegtbaatar, reconstructed partly on the basis of Kryptobaatar(abducted limbs). The quadratus lengths of the pelves ofboth taxa have been femoris adductor brevis enlarged to the same size to make comparisons easier. Al' Bl' beginning of propulsive phase; adductor longus A" B" middle of propulsive phase; DA" B" end of propulsive phase. Bold lines in Al and �j----+--- adductor magnus A3 Bl illustrate how moment arm has been measured for adductor magnus. Moment arms for other muscles were measured in the same way. Scale bars 10 mm. (See also Table 4.)
adductor magnus
the pelvic musculature in Rattus is generally the same as in 49B1), adductor longus and add. magnus prevented the Meriones and Antechinus (Fig. 38). caudal movement of the femur. In Nemegtbaatarthe muscle Figs. 48 and 49 illustrate a diagrammatical comparison of attachments of these two adductors are relatively large, the geometryofthe bones and muscles ofthe hip joint during which indicates their great mass. the propulsive phase in caudal and lateral views in Rattus and The moment arm alone, without estimation ofthe force of Nemegtbaatar (based in part on Kryptobaatar). The moment a muscle, is relatively uninformative, but the ratio of adduc arm of a muscle that medially retracts the femur is the tor to retractor moments allows one to evaluate the main distance between a point on the fem oral head at the axis of function ofa given muscle. As can be seen in Table 4, all the rotation (fulcrum) and the muscle; the moment arm is adductors and quadratus femoris in Rattus have retractor perpendicular to the direction of contraction of the muscle moments greater than a sum of all adductor moments. In fibers (bold lines in Figs. 48Al, Bl and 49Al, Bl)' We deter Nemegtbaatar, however, the adductor moments for all the mined angles of the direction of muscle contraction between adductors and quadratus femoris are greater than the retrac the pelvis and femur by measuring angles between the hori tor and protractor moments. This shows that in Rattus the zontal plane (perpendicular to the sagittal plane in caudal main movements of the femur are due to retraction (in a view) and the direction of the muscle contraction. Figs. 48 craniocaudal direction). For this reason add. longus is rela and 49 and Table 4 give the data on the moment arms of the tively small, its mass being 7-8% of a sum of the mass of all retractors of the hip joint in Rattus and in Nemegtbaatar. In the adductors of the femur and quadratus femoris Rattusthe retractors during the entire propulsive phase work (measured by us). In contrast, the main movements in to move the femur caudally, with the exception of adductor Nemegtbaatar were due to the action of the adductors (in longus, which during the end of the phase (Fig. 49A3) pre both medial and craniocaudal directions). In Nemegtbaatar vents furthercaudal movement of the femur; in this position the relatively great protractor moments of add. magnus and adductor longus acts as a protractor ofthe femur. In Nemegt add. longus and the reduced retractor moments of add. baatar, during the beginning of the propulsive phase (Fig. brevis and quadratus femoris resulted in a more vertical shift FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 69
Fig. 49. Same taxa and skeIetal parts as in Fig. 48, in lateral view. For explanations, see Fig. 48. Scale bars 10 mm.
rf::;o�f------quadratus femoris
__� adductor brevis .\::-:#'-��Q:c_ __ tt------adductor longus
- � -- '-..c- ---- adductor magnus -__ + + __� d-J
of the pelvis than in therian mammals (in which the protrac had a very steep trajectory of jump, they possibly did not tor moment ofadd. longus is very small and add. magnus has develop the gathered phase. only the retractor moment). The great retractor moments The main difference in the mechanics of the propulsive hinder the anterior excursion of the pelvis (and body). phase in therians and multituberculates is that in therians Therefore we speculate that in multituberculates the pelvis retraction of the femur predominates (designated here moved steeply vertically during the propulsive phase (as retractoral mechanics), whereas in multituberculates adduc illustrated in Figs. 51-53) which resulted in a steep jump tion predominates (adductoral mechanics). For retractoral trajectory. mechanics it is important that the adductoral component is In extant, small, fast -running mammals the two phases of balanced by the action of the gluteals. Therefore, in Rattus flightoccur only in fo rms in which the angle oftak e-offisless norvegicus the mass of m. gluteus medius is 1.3 times greater than 7°. lf the angle is greater, the hind limbs touch down than the combined mass of all the adductors and quadratus before the fo relimbs take off,and the phase of gathered flight femoris (Gambaryan, in preparation). This shows that glu does not occur (Gambaryan et al. 1978). lf multituberculates teus medius, working as an abductor, balances the action of 70 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
Table 4. The moment arm of muscles at the hip joint (in millimeters, ally. At that time the moment arm of iliopsoas was the measured in Figs. 48 and 49 and enlarged x2) and angle of muscular greatest and that of gluteus medius the smallest (Fig. 50A). contraction between the pelvis and fe mur (in degrees) in Rattus and Nemegtbataar during the propulsive phase. During the propulsive phase the rotation of the fem ur in creased, the moment arm of gluteus medius increased and Muscles Rattus Nemegtbaatar the moment arm ofiliopsoas decreased (Fig. 50B, C). At the Part of prop. phase Part of prop. phase end of the propulsive phase the dorsal surface of the femur 2 3 2 3 was directed cranially, as in modem therian mammais. For the pronation (medial rotation) of the femur it is desirable Moment arm: lateral view that the force of gluteus medius would act parallel to the Adductor longus R 16 R2 P13 RI P 16 P 21 sagittal plane. The prolongation of the ilium and the reflec Adductor brevis R23 R26 R25 R8 R8 R7 tion of its cranial ends in Nemegtbaatar (seen in Kryptobaa Adductor mag. R35 R37 R31 Ril P 23 P 31 Quadratus fe m. R9 RIO RIO R5 R7 R7 tar, Fig. 3A) contribute to this aim. Gluteus medius At the end of the propulsive phase, m. gluteus medius pars sacralis R6 R4 R4 R3 R3 R4 started to act as an abductor and retractor of the femur. We R4 pars iliacus R 14 RIS RIS R6 R6 speculate that this caused in multituberculates an increase in I +/- 103/0 94/0 92/13 34/0 24/39 22/52 the size of the greater trochanter, elongation of the femoral Angle neck and the medial shiftof the head, and at the same time an Adductor longus B24 B 84 B 140 A 124 A 156 A 175 elongation of the ilium for the insertion of the powerful Adductor brevis B4 B8 B3 A42 A45 A35 gluteus medius. Adductor mag. B13 B40 B80 An A 158 A 178 We also suggest that the dorsocaudally open (referred to Quadratus fe m. B 14 B 16 B 12 A36 A28 A22 usually as dorsally open) structure of the multituberculate Moment arm: caudal view acetabulum, may be due to the action of the retractor Adductor longus +19 +15 +20 +19 +19 +22 muscles. During the vertical movement of the pelvis, the Adductor brevis +11 +10 +13 +14 +12 +19 Adductor mag. +37 +34 +35 +27 +31 +35 main pressure of the femoral head in multituberculates was Quadratus fe m. -5 -5 -3 +10 +9 +10 directed ventrally rather than dorsally, and that is why the Gluteus medius acetabulum remained open dorsocaudally. pars sacralis -10 -1 1 -8 -19 -16 -17 The acetabulum is open dorsally in some modem therian pars iliacus -15 -18 -15 +8 +8 -3 mammals, as for example in Petaurista (Elftman 1929) and I +/- 68/26 79/16 86/20 67/30 59/34 76/19 Desmana (Gasc & Gambaryan, in preparation), which is Angle related to gliding and swimming habits, respectively. In both Adductor longus B 35 B 50 B33 A38 A28 A 19 these types of locomotion, the femur is abducted at alm ost Adductor brevis B49 B 38 B25 A44 A42 A34 right angles to the sagittal plane, which results in an open Adductor mag. B30 B40 B 31 A28 A 16 A 14 Quadratus fem. B 50 B 53 B46 A45 A42 A35 acetabulum. Elftman (1929) stated that the acetabulum is open dorsally in arboreal marsupials such as Didelphis and Parts of the propulsive ph ase: l beginning; 2 middle; 3 final. += adduction; Pseudochirus. We have not had an opportunity to examine - = abduction. A = above horizontal plane; B = below horizontal plane; Pseudochirus, R = retraction; P = protraction; mag. = magnus; fe m. = femoris. the skeletons of but in several specimens of Didelphis examined by us we have not fo und the dorsally open acetabulum. We also examined skeletons of two other arboreal marsupials, Trichosurus velpecula and Phalanger all the adductors and quadratus femoris; at the same time all maculatus, and in both of them we fo und the acetabulum these muscles act as retractors of the femur (Table 4). dorsally closed. For adductoral mechanics it is important to reduce the Simpson & Elftman(1 929) reconstructed the movements retractor component, and therefore this is partly balanced by of the femur in ? Eucosmodon sp. and noted its rotation and the protractors. The complete reduction of the retractor abducted position. Jenkins & Krause (1983) argued that in component is, however, impossible, as in such a case the Ptilodus the femur was abducted about 45° fromthe sagittal anterior propulsion would disappear and the jump would be plane. We speculate that the multituberculate femur was vertical. In multituberculates, in order to retain the retractor abducted from60° at the beginning of the propulsive phase component, the femur rotated and therefore gluteus medius to about 30° at the end. Abduction greater than 60° was apparently acted differentlyin Nemegtbaatarthan in Rattus. physically impossible, as in such a position the greater tro In Nemegtbaatar the lesser trochanter is very prominent, chanter would interfere with the ilium (Fig. 48B[). During situated in the middle of the ventral surface of the fe mur, the beginning of the propulsive phase, the adduction of the while in Rattus it is much smaller, placed at the medial femur displaced the pelvis strongly craniodorsally (Figs. 51- margin of the femur. We infer that in multituberculates, m. 53). The range of pelvic movement decreases exponentially iliopsoas rotated the femur to such extent that its dorsal with the decrease of the angle of abduction, as it depends on surface at the beginning of the propulsive phase faced later- the cosine of the angle (Figs. 48 and 51). An abduction ofless FOSSILS AND STRATA36 (1994) Anatomy and habits of multituberculates 71
cond. trochanter lateralis minor caput ossis femoris
trochanter
minor
Fig. 50. Nemegtbaatar gobiensis (ZPAL MgM-I/8l). Diagram illustrating inferred rotation of right femur around longitudinal axis during beginning (A), middle (B) and end (C) ofthe propulsive phase. Femur is seen in proximal view. In A the ventraI side is up; in B and C it is moved to the left.Black circle on femoral head denotes center of rotation; m = medial condyle (condylus medialis ). U pper arrow denotes direction of constriction of m. iliopsoas, lower arrow of m. gluteus medius and m. gluteus profundus. Scale bar 5 mm.
than 300would move the pelvis only insignificantly upwards gravity, the tail at the end of the propulsive phase moves and would not result in an increase of the thrust of propul ventrally, as demonstrated by Fokin (1978, Figs. 6, 9, 11, 15) sion. On this basis we suggest that the femur possibly did not fo r many rodents. However, in some modern mammals, the abduct less than 30° in multituberculates. impulse of the fo rce oflimbs extends caudal to the center of The main difference between the hind-limb movements the gravity. In such fo rms, (e.g., Pygerethmus; see Fokin 1978, of multituberculates and those of modem therians is that in Fig. 10) at the end of the propulsive phase the tail moves multituberculates adduction of the femur took place during upwards, in order to balance the ventral rotation of the the whole propulsive phase (Fig. Sl). In therians there is no anterior part of the body. We speculated under 'Function of adduction of the femur during the propulsive phase (Jenkins the pelvic muscles' that multituberculates had a steep trajec & Camazine 1977). Whereas in therians the distal end of the tory of jumps. If so, the impulse of the fo rce of limbs was femur moves only in a parasagittal plane during the propul directed craniodorsally, caudal to the center of gravity. sive phase, in multituberculates it moved in both parasagittal Therefore we believe that before the take-off, the multi and transverse planes. tuberculate tail had to move upwards (Fig. 52), as in Figs. 51-53 present the inferred movements of the hind Pygerethmus. limbs and pelvis in multituberculates (in Nemegtbaatar, Aristov et al. (1980) demonstrated that a long, heavy tail based in part on Kryptobaatar) during the propulsive phase commonly occurs in smallterrestrial mammals and acts as a in caudal, lateral and dorsal views. At the beginning of the balancing organ not only during jumping, but also during propulsive phase the femur (as argued above) lay about 60° turning. The tail is also used as a prehensile organ in many to the parasagittal plane and the pes stroke the ground with arboreal mammals. all the phalanges. During propulsion the ungual phalanges Krause & Jenkins (1983) regarded the tail of the Paleocene remained at the same place, but at the end the firstand fifth multituberculate Ptilodus kummaeto be prehensile and cited digits were clear ofthe ground. During propulsion the femur four characters that they considered characteristic for pre adducted and rotateed cranially about its longitudinal axis hensile-tailed mammals: great length of the tail; haemal (upper arrows in Figs. 51 and 53, curved arrow in Fig. 52); the arches developed along nearly the entire length of the tail; crus rotated in the knee joint and the calcaneal tubercle (and robust transverse processes; and large sacral spinous pro tarsus and metatarsals) rotated laterally (lower arrows in cesses, nearly equalling in height the spinous processes ofthe Figs. 51 and 53). As a result of the hind limbs movements and posterior lumbar vertebrae. All these characters occur in rotation, the pelvis was shiftedcraniodorsa lly. arboreal mammals, but at the same time they are fo und in terrestrial running and jumping mammals. We have exam Macropus rufus, Petrogale penicillata, Function of the tail ined the skeletons of Elephantulus rozeti, all the species of Allaetaga, all the species In modem small therian mammals, during the propulsive of all the genera of the Dipodinae, and many others, and we phase the impulse of the fo rce of the limbs is directed cranio have fo und these fo ur characters in all of them. The only dorsally. If this impulse extends cranial to the center of fe ature that characterizes prehensilityand is absent in terres- 72 ZofiaKielan -Jaworowska & Petr P. Gambaryan FOSSILS ANDSTRATA 36 (1994)
trial fo rms is the com (a local hardening and thickening of the skin, formed especially on the toes) on the ventral side of the tail, which is not preserved in fo ssils. In modem mam mals the com on the tail occurs, fo r example, in Arctictis binturong (Viverridae) and Brachyteles arachnoides (Ce bidae). In these and many other taxa with com, the vertebrae in the area of com widen and then at the very end of the tail they narrow again. This is the only character that allows one to define theprehensile tail in fo ssil mammals, which, how ever, is not known in multituberculates (induding Ptilodus, see Krause & Jenkins 1983, Table 2). The few caudal verte brae preserved in Kryptobaatar and Catopsbaatar and the structure of the lumbar vertebrae in Nemegtbaatar (see 'Os teological descriptions') allow us to assume that the tail in the studied Asian multituberculates was long and similarly built as in Ptilodus.
Function of the transverse processes In Nemegtbaatar the transverse processes of the lumbar vertebrae are robust (Figs. 11, 35, 36B); their lengths relative to the distances between the prezygapophyses and postzyga pophyses are greater than in most taxa cited in Table 2 and smaller only than those of Lepus europaeus, which belongs to a different size category. With 'parasagittal' position, the limbs strike the substrate dose to the sagittal plane. Because of this the force rotating the pelvis, sacrum and the lumbar vertebrae around the Fig. 51. Diagram illustrating inferred movements of hind limbs and pelvis longitudinal axis is relatively small (Jenkins & Camazine in Nemegtbaatar (based in part on Kryptobaatar), at beginning (bold lines) and end of propulsive phase, in caudal view. Upper arrow denotes cranial 1977, Table I). With abducted position this force increases. rotation of femur about its longitudinal axis; lower arrow denotes lateral In Nemegtbaatar the long transverse processes are possibly rotation of tarsus. See text for explanation. Scale bar 10 mm. an adaptation for balancing the force of the vertebral rota tion during the propulsive phase. In ?Eucosmodon sp. and Ptilodus kumrnaethe spinous and transverse processes were approximately as long as in Nemegtbaatar (Krause & Jenkins third digit in the pes of Kryptobaatar are relatively longer 1983, Figs. 1, 2,7and 28). than in extant mammals cited in Table 5. Relatively short Abducted limbs occur in amphibians and reptiles, which tibia and metatarsals would indicate that Kryptobaatarwas employ symmetrical locomotion with strong lateral flexures running rather slow, similar to, for example, Cricetulus mig of the body. In relation to this the transverse processes of the ratorius (4 m per second; unpublished experimental data of lumbar vertebrae are short, as their elongation would hinder Gambaryan). the lateral flexures. The long transverse processes of the However, there is a contradiction between the data ob lumbar vertebrae in multituberculates thus indicate asym tained from the lengths of the spinous processes of the metrical locomotion. lumbar vertebrae (which indicate long jumps in studied multituberculates) and those obtained fromrelative lengths Proportions of hind limb segments of the hind-limb segments (which indicate relatively short jumps). This contradiction may be the result of the ab As may be seen in Table 5, the tibia in Kryptobaatar is ducted position of multituberculate limbs, because ofwhich relatively shorter than in slow runners such as the Cricetidae their movements were different frommammals with 'para (Mesocricetus raddei) and terrestrial Sciuridae (Citellus xan sagittal' limbs. The direct transposition of data obtained thoprymnus and C. fulvus). Mt III in Kryptobaatar (com fromthe analysis of gaits in modem mammals would thus pared to the length of the femur) is relatively longer than in be incorrect. Mesocricetus raddei and Cricetulus migratorius, and similar to In order to understand the mechanics of multituberculate that in the terrestrial Sciuridae, but shorter than in taxa more locomotion, we made an attempt to compare it with that of specialized for jumping (Table 5). Only the segments of the frogs,which are the only modem vertebrates that use asym- FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 73
Fig. 52 (left).Diagram illustrating inferred movements of hind limbs, pelvis and tail in Nemegtbaatar (based in part on Kryptobaatar) during beginning (A), middle (B; bold lines) and end (C) of propulsive phase. Epipubic bone omitted. Straight arrow denotes direction of force of propulsion; round arrow denotes rotation of fe mur. See text for explanations. Scale bar 10 mm.
Fig. 53 (right). Diagram illustrating inferred movements ofhind limbs, pelvis and sacrum in Nemegtbaatar (based in part on Kryptobaatar) during beginning (A), middle (B) and end (C) of propulsive phase, in dorsal view. Straight arrows denote direction of fo rce of propulsion; leftround arrows denote rotation of femur, round right arrows denote rotation of calcaneal tubercle. See text for explanation. Scale bar 10 mm.
metrical jumps with abducted limbs. In frogsthe trajectory metrical and two others asymmetrical, the asymmetrical of jump is verysteep : the angle of take-offis 30-35° (Gans ones were classified by him as gallop ('andar galopado'). 1961, 1974) or even 45° (Gray 1968). We speculate that in Ameghinichnus had the hind limbs more abducted than the multituberculates during the jump the hind limbs probably fo relimbs and was digitigrade. At the beginning of gallop it moved rapidly medially (as in frogs), which resulted in a placed the forelimbs slightly to the rear and inside the hind jump trajectory that was higher than in modem therian limbs. In the second phase of gallop all four feet were placed mammais. In small mammals with 'parasagittal' limbs stud approximately at the same transverse line. The tracks are ied byus, afterthe propulsive phase the center ofgravity takes roughly reminiscent of those of Microtus gud and Alticola offat 3-10° to the horizontal plane (Gambaryan 1974; Gam strelzovi figured by Gambaryan et al. (1978). Casamiquela baryan et al. 1978), and the trajectory of their jump is very attributed Ameghinichnus tentatively to Pantotheria. Al low. though the evidence is inconclusive, we believe that it might Casamiquela (1964; see also Leonardi 1987) described the belong to multituberculates which we regard as digitigrade tracks of a small mammal designated Ameghinichnus pata (see below). If so, these tracks would indicate that multitu gonicus from theLate Jurassic of Patagonia. He attributed to berculates employed both symmetrical and asymmetrical Ameghinichnus three types of tracks, one of which is sym- gaits with jumps. 74 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
Table 5. Lengths of the hind limb segments in pereent of the femur length, Szalay (1993) studied the tarsus of?Eucosmodon and iso and the jumping index. lated calcanea and astragali of a ptilodontoid fromthe Gryde
Cato Speeies Tibia Mt DIll DIll Ind Hab Locality of the Frenchman Formation, Alberta, and recon No. m Phi Ph2 structed relevant tarsal joints. His reconstruction of? Eucos modon 41 Kryptobaatar dashzevegi 84 33 22 16 pes is similar to those of Granger & Simpson (1929) 1110 Marmosa sp. 121 25 19 12 and Krause & Jenkins (1983). 1380 Elephantulus rozeti 140 72 14 9 11 We reconstruct the pes ofKrypt obaatar (Fig. 54) primarily 46 Sciurus persicus 114 36 18 14 6-7 on the basis of ZPAL MgM -I!41 (Figs. 2, 6A-C, 7) in which 175 Citel/us fu lvus 98 32 17 11 2-3 159 Citel/us xanthoprymnus 100 30 19 10 3-4 both pedes have been preserved in articulation, and on the 59 Spermophilopsis leptodactylus 108 34 19 13 6-7 basis of an articulated leftpes of Chulsanbaatar, ZPAL MgM 79 Glis glis 107 34 21 13 5-6 I/99b (Fig. 25). We also used in this reconstruction uniden 83 Rattus norvegicus 113 43 18 11 4-5 tified multituberculate hind-limb elements from the Late 11 Mesocricetus raddei 91 21 11 9 1-2 314 Mesocricetus brandti 92 19 10 6 1-2 Cretaceous ofN orth America (Fig. 55), on which the articu 311 Cricetulus migratorius 104 29 13 10 4-5 lar surfaces are weU preserved. We present a new reconstruc 403 Calomyscus bailwardi 129 57 20 13 6-7 tion of the pes of?Eucosmodon on the basis ofAMNH 16325 428 Meriones tamariscinus 116 46 18 12 6-7 (Figs. 56, 57). Although pedes of Kryptobaatarand ?Eucos 114 Meriones meridianus 131 53 21 12 7-8 117 Allactaga jaculus 139 93 26 15 14-15 modon differfrom one another in details, they share fe atures that we regard as characteristic of multituberculates as a Cat. No. (eatalogue number) refers to ZPAL MgM-1/ colleetion for Kryp- whole. In our reconstruction the astragalus is placed ob tobataar and to ZIN, Laboratory of Mammals eolleetion for extant taxa.
D = digit; Hab = habits; lnd = jumping index (ratio of jumping distanee liquely lateroproximally to mediodistally with respect to the to body length); Mt = metatarsal; Ph = phalanx; r = ricoehetal; s = tuber calcanei, Mt III is abducted about 30° fromthe longitu seansorial; t = terrestrial. Jumping indexes are given after experimental dinal axis of the tuber calcanei, and Mt V articulates with the unpublished data of Gambaryan (see Gambaryan et al. 1978 for deserip- distal margin of the calcaneum medial to the peroneal tion ofmethods). groove. In the three pedes of Mongolian multituberculates men tioned above, the distal part of the tarsus is preserved in its Structure and function of original position in articulation with the metatarsals. Our multituberculate pes observations on the movements at the astragalonavicular joint in multituberculates agree with those ofSzalay (1993). In cursorial therian mammals the pes as a rule is situated There is an extensive concave facet on the navicular, fo r paraUel both to the sagittal plane and to the direction of articulation with the astragalus. In Mongolian multitubercu movement. In animals with abducted limbs the pes may be lates the astragalus is directed obliquely, but in Kryptobaatar placed in various positions. For example, in Ornithorhynchus it has been slightly shiftedfrom its original position on both the manus is directed almost parallel to the direction of sides. In spite of the shifting it is obvious that the saddle movement, and the pes lies at an angle of about 70° (Prid shaped fa cet on the mediodistal side of the astragalus (at the more 1984, Fig. 1). In Tachyglossus the manus is directed base ofthe 'astragalar head' of other authors), which extends mediaUy, at about 60°, and the pes is directed laterally at below the short margin (medial in the reconstruction of about 70° (Jenkins 1970a, Fig. 2). In lacertilians the manus ? Eucosmodon by Granger & Simpson 1929, and medio distal and pes may be placed from transverse to almost paraUel in our reconstructions of Kryptobaatar and ? Eucosmodon - positions to the direction of movement (Sukhanov 1974; Figs. 54, 57), articulated with the concave facet on the proxi Leonardi 1987). mal margin of the navicular. In an isolated unidentified The first multituberculate pes ever fo und was that of multituberculate astragalus from the Late Cretaceous of ?Eucosmodon sp. (AMNH 16325) fromthe Early Paleocene North America (Fig. 55B-D) and in ?Eucosmodon sp. (Fig. of New Mexico, reconstructed by Granger & Simpson 56C, D), the astragalonavicular facet is similarly extensive as (1929). In their reconstruction (Fig. 23) Mt III is arranged in Kryptobaatarand extends fromthe medio distal astragalar parallel to the longitudinal axis of the tuber calcanei, and the process medially around the corner below the shorter mar distal part of the calcaneum is 'hanging in the air' and is not gin of the astragalus. If one would place the astragalus trans supported distally by any tarsal or metatarsal bone. versely, only a part of the astragalonavicular facet would The skeleton of? Eucosmodon sp. was subsequently studied match the concave fa cet on the navicular. by Krause & Jenkins (1983) and Jenkins & Krause (1983). We made an attempt to place all of the tarsal bones of They estimated that the longitudinal axis ofthe fo ot (passing ?Eucosmodon sp. (AMNH 16325) in various positions, so along the third ray) deviated 30-400 from a sagittal plane. that all of the articular facets of all the bones would fit one They demonstrated a wide range of the pedal mobility (es another, and only in the position shown in Fig. 57 did we pecially abduction) in ? Eucosmodon and Ptilodus, character obtain a perfect match. In this position the surface of the istic for arboreal mammals that descend trees headfirst. calcaneum bearing sustentacular and astragalocalcaneal FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 75
facets, and usually referred to as dorsal (e.g., Krause & groove on the cuboid and then extends to Mt I. In Tachy Jenkins 1983, Fig. 24; Szalay, 1993, Fig. 9.10), is placed glossus the tendon of m. peroneus longus, as stated by Lewis obliquely medially, and the tuber calcanei is shifted in a (1963, p. 57), 'enters the sole through an aperture between plantar direction relative to the metatarsals (Fig. 57e, D). the calcaneus and the cuboid. After establishing a slender In Kryptobaatar the proximal end of Mt V protrudes attachment to the base of the fifthmetatarsal, the major part proximally, and there is a small facet on it that fits thedistal of the tendon crosses the sole obliquely, as in other mam margin of the calcaneum medial to the peroneal groove. A mals, to be inserted on the flattenedand disc-like firstmeta small medioproximal facet on Mt V articulates with the distal tarsal.' part of the lateral margin on the cuboid. In ? Eucosmodon on A peroneal groove on the multituberculate calcaneum can the plantar side of the distal margin of the calcaneum there is only be interpreted as housing the ten don of peroneus a facet for articulation with Mt V. On the proximal margin of longus, as correctly recognized by Szalay (1993). However, in Mt V, on the dorsal side, there is a distinct oblique facet (seen his reconstruction (Szalay 1993, Fig. 9.10), the peroneal in Fig. 23 ofGranger & Simpson 1929 and in Fig. 24 ofKrause groove points laterodistally rather than towards the bone & Jenkins 1983) for articulation with the distal end of the housing the distal part of this tendon. In modem mammals, calcaneum. the bones of the pes with grooves fo r the tendon of peroneus In all of the multituberculate calcanea the prominent longus contact one another (see, e.g., Lewis 1963, 1989; laterodistal peroneal tubercle is separated fromthe calcaneal Evans & Christensen 1979; Schaller 1992; and others). We body by a deep gro ove (e.g., Figs. 55F-I, 56J). In some reconstruct the course of this tendon in ?Eucosmodon (Fig. marsupials and rodents along a groove on the lateral surface 57) as passing along the bones that contact one another: of the calcaneum there extends the tendon of m. peroneus extending along the dorsal side ofthe calcaneum and passing longus; This tendon passes along the notch on Mt V to the through the peroneal groove onto the plantar side to Mt V,
f \ f \ I \ f I \ I I I I I V, I i \"-.( I f \ \ I \ t I f \ t I f t I I f \ I V V B \ I \ t f I \ \ , \ l/ -0
Fig.54. Reconstruction of right pes of Kryptobaatar dashzevegi (ZPAL MgM-I/41), in dorsal (A), plantar (B), medial (C) and lateral (D) views.Phalanges not preserved are shown in A and B by dashed lines. Sesamoid bones not preserved in Mt I have been reconstructed. In A and B metatarsals and phalanges are drawn in the same plane. Scale bar 5 mm. 76 ZofiaKielan -Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
Fig. 55. Unidentifiedmultituberculate postcranial elements from theLate Cretaceous of North Ameriea. DA. Lefttibia, distal view (AMNH 117143). DB, C, D. Rightastragalus (AMNH 118887), distal, dorsal and plantar views. In B the medioproximal margin is up; in D it is down. DE, F, G. Leftcalcaneum (ZPAL Z.p. M/123), distal, medioplantar and dorsolateral views. OH, l. Right calcaneum (AMNH1 17990), laterodistal and dorsal views. Calcaneum in H is arranged at 45° in respect to position in I and therefore appears smaller. A is fromthe Lull Il locality UCMP-V5620, Wyoming, all others fromthe Bug Creek Anthills site, Hell Creek Formation, Montana. l = medial malleolus; 2 = lateral condyle; 3 = mediodistal proeess of astragalus ('astragalar head'); 4 = saddle-shaped facet on astragalus for navicular; 5 = astragalocalcaneal facet; 6 = sustentacular facet of astragalus; 7 = astragalocalcaneal facet; 8 = sustentacular facet of calcaneum; 9 = peroneal groove; 10 = cuboid facet; arrow in A = pit for lig. collaterale mediale; arrow in H = cuboid facet. All x6; stereo-pairs coated with ammonium chloride. FOSSILS AND STRATA36 (1994) Anatomy and ha bits of multituberculates 77
Fig. 56. Isolated right bones of ?Eucosmodon sp. (AMNH 16325), Nacimiento Formation, Early Paleocene, locality east of Kimbetoh, San Juan Basin, New Mexico. DA, B. Navicular in plantar and proximal views. De. D. Astragalus in dorso-laterodistal and laterodistal views. DE, F. Distal part of the tibia in craniomedial and distal views. OG. Cuboid in lateral view, proximal margin is to the left.DH-J. Calcaneum in lateral (slightly distal), medial (slightly distal) ' and dorsal views. l = facet for astragalus in navicular; 2 = mediodistal process of astragalus ('astragalar head ); 3 = groove for tendon of m. peroneus longus in cuboid; 4 = medial malleolus; 5 = lateral condyle; 6 = medial condyle; 7 = sustentacular facet; 8 = cuboid facet; 9 = astragalocalcaneal facet; 10 = peroneal groove; arrows in A and B = distoplantar facet for articulation with ectocuneiform and mesocuneiform; arrow in D = saddle-shaped facet on astragalus for navicular. All X4; stereo-pairs, coated with ammonium chloride. 78 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 ( 1994) then along the grooves on the plantar side of the cuboid and the malleolus, as seen in an unidentified multituberculate ectocuneiform onto Mt Il, distal to the small tuber on the tibia (arrow in Fig. 55A), there is a deep pit for the liga plantar side ofMt Il, and finallyreaching Mt I (see also details mentum collaterale mediale. This pit is also preserved, but of individual bones in Figs. 55 and 56). If this were not the less clear, on the tibia of Nemegtbaatar (arrow in Fig. 17G). case, the presenee of the peroneal groove would be a puzzle. Ligamentum collaterale mediale inserted on the astragalus. In the right astragalus (AMNH 118887) from the Hell Krause & J enkins, ( 1983, Fig. 30) described the rotation in Creek Formation of Montana, on the plantar surface there the tibioastragalar and astragalocalcaneal joints in ? Eucosmo are two facets (Figs. 55D, 58). The astragalocalcaneal facet don sp. We measured the rotation in these joints in ?Eucos (lateral) is semilunar, as fo und by Krause & Jenkins (1983) in modon sp. and found that the rotation in the tibioastragalar Ptilodus kummae. The sustentacular facet (medial) is almost joint (about 30°, around the longitudinal axis of the tibia) entirely circular. If one would move the astragalus in a was possibly more extensive than in the astragalocalcaneal horizontal plane around the midpoint of the sustentacular joint (about 25°, around the same axis), the shared rotation facet, 10-15° each way, then on the middle part of the being about 55°. In recent eutherian mammals, in contrast to astragalocalcaneal facet one would produee a trace that cor multituberculates, rotation at the tibioastragalar joint is not resp on ds almost exactly to the astragalocalcaneal (lateral) possible because of the trochlear structure of the astragalus facet of the calcaneum (as seen in a dorsal horizontal projec (Szalay 1984). tion) (Fig. 58). In some marsupials, however, e.g., Didelphis marsupialis, The medial malleolus of multituberculate tibia fits the Phalanger maculatus, Trichosurus vulpecula, Antechinus craniomedial side of the astragalus. On the medial surface of stuarti and Marmosa sp. (personal observations by PPG), in
Fig. 57. Reconstruction of right pes of ?Eucosmodon sp. (AMNH 16325), dorsal (A), plantar (B), medial (C) and lateral (D) views. Note the tendon of m. peroneus longus in A and B. Reconstruction of all digits is tentative, based on isolated phalanges. The pes is reconstructed with the adducted position of the firstdigit. In A and B metatarsals and phal anges are drawn in the same plane. Sesamoid bones are reconstructed. Scale bar lO mm. FOSSILS AND STRATA36 (1994) Anatomy and habits of multituberculates 79
locomotion, in which the gastrocnemius constricts during the whole duration of the propulsive phase. Jenkins (197la) 4 described in cynodonts an incipient tuber calcanei, which 3 indicates that the plantar aponeurosis possibly inserted 2 1 partly on the calcaneum. In symmetrical locomotion the load on the tarsal joint is relatively small, as it is responsible only for retaining the speed of the gait. With asymmetrical jumps the pressure on the tarsal joint increases, and the tuber calcanei (which acts now as a lever for gastrocnemius) en larges. At the same time the proximal part of the pes raises and becomes digitigrade. This confirms the condusion of
Fig. 58. Diagram based on an unidentified multituberculate astragalus Kuznetsov (1985) that digitigrady is an early mammalian (AMNH 118887) showing different positions of astragalocalcaneal facet adaptation. We reconstruct the multituberculate pes as during movement of astragalus on calcaneum. Plantar view. l = original digitigrade (contra Simpson & Elftman19 28). position; 2 = 5° of the original position, 3 = 10°, 4 = 15°. Scale bar 2 mm.
Pedal adaptations of Asian and North addition to the rotation (pronation-supination as in eu American multituberculates therians) between astragalar head and navicular, there is also a rotation in the tibioastragalar joint (abduction-adduction) The pedes of Asian taxa studied here differ in many details as in multituberculates. This rotation is possible because of from those of the North American genera Ptilodus and the lack ofthe trochlea and presence ofthe flattuberde on the ?Eucosmodon described by Krause & Jenkins (1983). In the dorsoproximal part of the astragalus. The tibial medial mal pes of? Eucosmodon the grooves on the dorsal surface of the leolus may rotate on the surface of this tuberde, around the astragalus are more prominent than in Kryptobaatar. The longitudinal axis of the tibia. calcaneum in ?Eucosmodon is relatively narrower, the astra We measured also the rotation in the astragalonavicular galocalcaneal facet is more prominent (buibous) and placed joint in ?Eucosmodon (30°, abduction-adduction) and in the doser to the sustentacular facet, the peroneal tuberde is less joint between the cuboid and the calcaneum (35°, flexion shiftedlaterally, and the peroneal gro ove is narrower. extension). On the laterodistal end of the navicular there We were not able to measure the mobilityin all the joints occurs a flatfa cet for articulation with the matching facet on of the pes in Asian taxa studied by us. It seems, however, that the cuboid. These facets are of the same size and are flat, the mobility at the astragalocalcaneal, astragalonavicular and which mayprevent movements at this joint. However, on the tibioastragalar joints was smaller in Kryptobaatarand Chul ectocuneiform and mesocuneiform there are proximal sanbaatarthan in ?Eucosmodon. We base this condusion on facets for articulation with a large distoplantar facet on the the structure of Kryptobaatarand Chulsanbaatarcalcanea, in navicular (arrows in Fig. 56A, B). This suggests that the flat which the sustentacular and astragalocalcaneal facets, al facets between the cuboid and navicular could separate dur though poorly preserved, are possibly less prominent and ing movements, as otherwise the movements between the more distant from one another than in ?Eucosmodon. In navicular and both ectocuneiform and mesocuneiform Kryptobaatarthe mediolateral diameter of the navicular is would not be possible. only slightly smaller than the maximal length of the astra In Kryptobaatar (ZPAL MgM-I/41) on both sides, the galonavicular facet of the astragalus (1.5 mm and 1.8 mm, calcaneum has been displaced in a plantar direction (Figs. 2, respectively); in ? Eucosmodon the diameter ofthe navicular is 6A, B, 7A-D). If one would place the calcaneum in its much smaller than the length of the corresponding facet on original position, as reconstructed in Fig. 54, the lo ad of the the astragalus (3.8 mm and 5.5 mm, respectively). This calcaneum on the cuboid would extend perpendicularto the demonstrates a wider range of the astragalonavicular move direction of movement of the pes (as it does in other mam ment in ?Eucosmodon than in Kryptobaatar. mals), rather than obliquely medially, as would appear from The dorsal surface of astragali is less undulate in Asian taxa the reconstructions of Granger & Simpson (1929) and than in ? Eucosmodon. In relation to this the distal condyles on Krause & Jenkins (1983). An abducted position of the multi the tibia are more prominent in ?Eucosmodon (Fig. 56E, F) tuberculate pes and the compulsion to retain the load per than in Kryptobaatar, Nemegtbaatar (see 'Osteological de pendicular to the direction of the movement explain the scriptions') and an unidentifiedtibia fromthe Lance Forma presence of an oblique, rather than distal (as in all other tion (Fig. 55A). mammals) cuboid facet on the multituberculate calcaneum. It would be interesting to compare the lengths of metatar In modem reptiles, m. gastrocnemius inserts on the plan sals and digits in Kryptobaatar and ?Eucosmodon and in tar aponeurosis (Romer & Parsons 1986). As argued by extant small marsupial and eutherian mammals of different Gambarjan (1990), this is an adaptation for symmetrical life-styles. In most scansorial mammals, e.g., Glis glis, Tricho- 80 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
23 Second phalanges surus vulpecula and Phalanger maculatus (Fig. 59), the fo urth 45 and fifth digits of the foot (but not the metatarsals) are the longest, which is an adaptation fo r holding branches. In 1111 1111 1111 1111I11 I 1111 1111 1111 1111 1111 1111 1111 Didelphis marsupialis elongation occurs but is less conspicu ous. Similarly, in Sciurus presicus, which can move freely between the ground and trees (as, e.g., Tupaia; Jenkins 1974), the elongation ofthe phalanges ofthe fo urth and fifthdigits is modest and may be seen only in comparison with purely terrestrial fo rms belonging to the same family, such as, e.g., Citellus xanthoprymnusand C.fu lvus (Table 5 and Fig. 59). In a terrestrial marsupial, Antechinus stuarti, the fo urth and fifth digits are not elongated and are similar to those in Citellus, Rattusand other terrestrial rodents (Fig. 59). Unfortunately, measurements of allthe phalanges for all 1�11111111111 �i��I�'illll [1111 11111 11111 11111 11111 111, the digits cannot be taken fo r any of the three multitubercu late genera (? Eucosmodon, Ptilodus and Kryptobaatar) in ABCDEFGH J KL & which incomplete pedes are known (Granger Simpson Fig. 59. Lengths of metatarsals of firstand second phalanges in percent of 1929; Krause & Jenkins 1983; and this paper). In the case of total length of hind limb along third digit without ungual phalange in ?Eucosmodon the association of individual phalanges with multituberculates and extant therian mammais. Phalanges enlarged x2 in particular digits is not certain. In Ptilodus the digits Il-V are respect to the metatarsals. The metatarsals and phalanges are numbered. Kryptobaatar DA. Kryptobaatar dashzevegi (ZPAL MgM-1/41). DB. Ptilodus kumrnae completely preserved, and in digits IV and V (UA 9001, after Krause & Ienkins 1983, Table 1). De. Antechinus stuarti are complete and in digits Il and III the unguals have not (ZIN 13951). DO. Mesocricetus raddei (ZIN 660). DE. Rattus norvegicus been preserved. Because of this we compare below the (ZIN 83). OF. Meriones tamariscinus (ZIN 428). OG. eitel/us fulvus (ZIN lengths of the second to fifthdigits without ungual phalanges 175). OH. Sciurus persicus (ZIN 800). Dl. Glis glis (ZIN 221). Dj. Didelphis Kryptobaatar, Ptilodus marsupialis (ZIN 66). DK. Phalanger maculatus (ZIN 10952). DL. Tricho of with similarly incomplete digits of surus vulpecula (ZIN 31713). C-G are terrestrial, H may move freely (rather than ?Eucosmodon) to make the comparisons more between the trees and ground, I-L are seansorial. Note elongation of credible. In Ptilodus (afterKrause & Jenkins 1983, Table 1) phalanges of O IV and O V in scansorial fo rms. The respective lengths ofthe the combined length of Ph l and Ph 2 ofD Il is 12.1 mm, D phalanges in multituberculates (A and B) are similar to those ofterrestrial rather than scansorial taxa. (See also Table 5). III 11.9 mm, D IV 11.8 mm and D V 8.3 mm. In Kryptobaatar the combined lengths of Ph 1 and Ph 2 are: D Il 8.3 mm, D III 7.9 mm, D IV 6.8 mm, D V 5.6. It followsthat both taxa show similar pattern of relative lengths of fo ot digits (without ungual phalanges): DIl > DIll > DIV > DV, the fifth being In three pedes of Mongolian multituberculates described notably shorter than D Il-D IV. This pattern differs from here (right and left pedes of Kryptobaatar and left pes of that characteristic of scansorial mammals (Fig. 59). Chulsanbaatar, Figs. 2, 6, 7, 25 and 54) the entocuneiform is The lengths of the first ray cannot be compared, but it is elongated and protrudes strongly distallybeyond the distal important to note that while in ? Eucosmodon and in Ptilodus level of the mesocuneifo rm, ectocuneiform and the cuboid. kummae Mt I is the shortest of all the metatarsals, in Krypto The joint between the metatarsal I and entocuneiform is of a baatar Mt V and Mt I are of the same length. hinge type and permits movements of Mt I in a dorsopIantar In Table 6 we give the lengths, widths and depths (the latter direction; it seems, however, that a very small abduction was measured in dorsopIantar direction) of Mt I and the ento also possible. In mammals with an opposable hallux, this cuneiform, as a percentage of the corresponding dimensions jomt is saddle-shaped, and the entocuneiform does not of MT III in multituberculates and small modern mammals protrude distally (or protrudes only slightly) beyond the of various life-styles. As may be seen in Table 6, Mt I in level of the other cuneiforms. In these mammals the ento ?Eucosmodon is smallerin all dimensions than that in Kryp cuneiform is wide relative to its length (Table 6) and the tobaatar. Mt I in ?Eucosmodon is smaller in width and depth entocuneiform-metatarsal I joint is placed mediodistally, or relative to Mt I in all modern mammals cited in Table 6, in medially (Lessertisseur & Saban 1967b; Starck 1979; Nowak particular in scansorial fo rms with an opposable hallux, as & Paradiso 1983; Gebo et al. 1991; and many others), rather for example Phalanger, Trichosurus, Marmosa and Didelphis. than distally as in Mongolian taxa. We conclude that the The relative dimensions of Mt I in ?Eucosmodon are compa hallux was not divergent in Kryptobaatarand Chulsanbaatar. rable (but a little smaller) to those of scansorial rodents, in Kryptobaatar and Chulsanbaatar differ from ?Eucosmodon which Mt I is not opposable, as for example Glis and Sciurus, (Fig. 57) and Ptilodus kummae (Krause & Jenkins 1983, Fig. and are similar to those of terrestrial rodents, such as Rattus, 27), where the entocuneiform protrudes less strongly distally Cricetulus and Citellus, and to the terrestrial marsupial Ant beyond the level ofthe other cuneiforms. As far as the relative echinus stuarti. lengths of entocuneiforms are concerned, the entocunei- FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 81
Table 6. Length, width and depth of Mt I and entocuneiform in percent to The shape of the ungual phalanges of the ? Eucosmodon the length, width and depth of Mt Ill. fo ot speaks against its scansorial mode of life. In the scan Cat. No. Speeies MT ! Entocuneif. H sorial mammals the ungual pedal phalanges are strongly L W D L W D compressed laterally and curved. Rose (1990), Van Valken
UA 9001 Ptilodus kummae 58 burgh (1987) and MacLeod & Rose (1993) studied the struc ZPAL MgM Kryptobaatar 73 71 112 33 168 ture of ungual phalanges of the manus in Paleogene and -I/41 dashzevegi some extant mammals. We were unable to make direct AMNH 16325 ?Eucosmodon sp. 63 70 58 29 116 108 comparisons with their data, as the only multituberculate ZIN 10952 Phalanger maculata 103 261 llO 28 466 142 s ZIN 31713 Trichosurus vulpecula 70 150 115 32 318 261 s unguals available to us belong to the hind limb. The pedal ZIN 1110 Marmosa sp. 86 180 76 12 316 unguals have been preserved in ? Eucosmodon and Krypto ZIN 66 Didelphis marsupialis 72 131 110 14 258 194 s baatar(Fig. 2B), but the latter could not be prepared fromthe ZIN 13951 Antechinus stuarti 57 86 100 26 114 100 matrix. The two pedal ungual phalanges of? Eucosmodon (of ZIN 379 Rattus norvegicus 54 90 88 33 112 142 ZIN 221 Glis glis 55 92 69 39 110 187 s undetermined digits) are wide and little curved and are ZIN 800 Sciurus persicus 77 83 107 20 100 214 s reminiscent of those of modem terrestrial mammals such as ZIN 203 Citel/us xanthoprymnus 62 71 100 30 130 137 t Citellus, rather than those of scansorial taxa such as Sciurus,
Cato No. = catalogue number; D = depth; H = habits; L = length; s = Glis and Marmosa (Fig. 60). As demonstrated by MacLeod &
seansorial; t = terrestrial; W = width. The measurements of Ptilodus Rose (1993), the ungual phalanges of the manus differ in kummae are fromKrause & Jenkins (1983, Table 1). mammals of various life-styles: in scansorial fo rms they are deep and narrow, similar to the pedal ones of scansorial fo rms shown by us in Fig. 60C-E. The pedal ungual phalanx of? Eucosmodon sp. (Fig. 60A) is reminiscent of those of the manus of cursorial and some fo ssorial forms figured by fo rm in ?Eucosmodon is, in fact, relatively longer than in MacLeod & Rose. However, the fo ssorial forms in question, Kryptobaatar (Table 6). As, however, the joint between the e.g., Cynomys ludovicianus and Marmota monax,mainly use navicular and entocuneiform in ?Eucosmodon is placed on the incisors for digging rather than the phalanges (personal the mediodistal side of the navicular, while in Kryptobaatarit observations by PPG). In addition, MacLeod & Rose (1993) is placed distally, the entocuneiform appears longer in Kryp did not provide the transverse sections ofthe phalanges, and tobaatarthan in ?Eucosmodon (Figs. 54 and 57). the comparisons of only the lateral and dorsal views may be The distal facet on the entocuneiform in ? Eucosmodon was misleading. referred to by Krause & Jenkins (1983) as saddle-shaped. If follows fromthe fo regoing comparisons that the pedes These authors argued that the entocuneiform-Mt I joint of Kryptobaatarand Chulsanbaatardiffer in manycharacters permitted both flexion-extension and abduction-adduc from those of ? Eucosmodon and Ptilodus. While arboreal tion of the hallux. The proximal part of the entocuneiform in adaptations of? Eucosmodon and Ptilodus might be possible, ? Eucosmodon is relatively narrower than in Kryptobaatarand Kryptobaatarand Chulsanbaatar do not show such adapta possibly permitted a considerable degree ofmobility (abduc tions in their pedal structure. We conclude that Kryptobaatar tion) in the navicular-entocuneiform joint, apparently lim and other Mongolian taxa studied by us were terrestrial ited in Kryptobaatar. runners.
I � A B E �
Fig. 60. Comparison of right ungual phalanges. Upper row- lateral view, middle- transverse sections along the lines shown in lateral and plantarviews, bottom - plantar view. DA. ?Eucosmodon sp. (AMNH 16325). DB. Citel/us xanthoprymnus (ZIN 159). De. Sciurus presicus (ZIN 800). OD. Glis glis (ZIN 221). DE. Marmosa sp. (ZIN 1110). Scale bars 2 mm. 82 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSliS AND STRATA 36 (1994)
Forelimb movements three planes arranged perpendicular to one another. The most important movements in this case are abduction, ad In small mammals during fast asymmetrical gaits the fo re duction and rotation, while flexionand extension are used to limbs work mainly to absorb the shock of landing; the a smaller degree. absorption increases with speed, steepness of the trajectory, The origins of m. coracobrachialis and biceps brachii (see and the animal's mass. We argued in the preceding sections 'Myological reconstructions') allow speculations on the that the multituberculate gait, when they were running fast, changes ofthese musdes at early stages ofmammalian evolu was asymmetrical and the trajectory of the jump was steeper tion. In cynodonts, as in modem reptiles, m. coracobrachi than in extant therians ofsimilar size and that because ofthis, alis longus, coracobrachialis brevis and biceps brachii were they did not have the gathered phase of flight. If so, their apparently present, all of them originating from the cora fo relimbs would act only for absorbing the shock oflanding. coid. During the reduction of the coracoid, all these origins In frogswhich usually also use asymmetrical locomotion, came dose to one another, producing an almost joint tendon the coracosternal joint is retained. In frogsthe short ribs do (as was probablythe case in multituberculates). In all reptiles not join the sternum, and the musdes connecting the fore and mammals m. biceps brachii inserts on the fo rearm, and limb with the sternum and coracoid on one side and with the the direction ofits excursion do es not interfere with the work thoracic vertebrae on the other side act as shock absorbers of the shoulder joint. Museulus coracobrachialis longus in (Gans 1961, 1974). serts on the humeral entepicondyle and can work only if the Eutherians, marsupials and, apparently independently, line of its excursion does not interfere with the lesser tu multituberculates solved the problem of absorption of the berde, and coracobrachialis brevis inserts on the crest of the shock of landing by the reduction of the coracoid to a small lesser tuberde. In multituberculates, because of the twisting proeess. The musdes of the shoulder girdle act as shock of the humerus, the entepicondyle is situated more ventrally absorbers and move the thorax vertically between the shoul than in therians and the line of excursion ofm. coracobrachi der girdle and fo relimbs. alis longus and m. coracobrachialis brevis extended along the Cheng (1955) described migration of m. supracora intertubercular gro ove (between greater and lesser tu coideus onto the scapula and its division into m. sup ra berdes). This gro ove in multituberculates is wider than in spinatus and infraspinatus in the embryological develop modem therians: in Nemegtbaatar ZPAL MgM-I/81 its ment of Didelphis. In primitive tetrapods the main function width is 36% of the humeral width at the level of the tu of supracoracoideus is to keep the body fromfa lling down berdes, in ?Lambdopsalis IVPP V8408 it is 36% and in IVPP wards between the limbs (Romer & Parsons 1986). The V9051 37%. In rodents this groove occupies 17-23% ofthe musde fibersof supracoracoideus are arranged horizontally. humeral width. The width of the groove and the twisting of In running laeertilians the forelimbs are only loaded slightly, the humerus in multituberculates allowed the work ofboth and the horizontal arrangement of the musde fibers issatis coracobrachialis musdes and movements of the shoulder factory to keep the body from saggingbetween the limbs. girdle. At the absorption of the shock of landing during the Acquisition of the 'parasagittal' position of the forelimbs asymmetrical gait, the main function of supracoracoideus in therian mammals resulted in reduction of the humeral increases, its fibersextend onto the scapula and are arranged twisting. This eventually caused the medial shiftof the cora vertically. This apparentlywas also the case in multitubercu coid pro cess and a secondary division of the origin of m. lates which used asymmetrical gaits when running fast and in coracobrachialis and m. biceps brachii. which supracoracoideus originated on the scapula. Romer & Parsons (1986, p. 296) stated that in mammals 'this major museular migration [of supracoracoideus l is presurnably Concluding remarks responsible fo r the reduction of the coracoid region of the girdle'. We agree, and we believe that the demand fo r shock We have argued that multituberculates had long spinous absorption eau sed migration ofthe fibersof this musde onto proeesses of the lumbar vertebrae and abducted limbs. the scapula, the disappearance of the coracostemal joint and Multituberculate locomotion is difficult to reconstruct, as reduction of the coracoid. apparently their gait when they moved fast was different Twisting of the humerus (Fig. 46) is correlated with the fromthose occurring in modern mammals. Although asym position of the fo relimbs. In animals with 'parasagittal' metrical, it cannot be dassifiedeither as primitive ricoehet, limbs, during the phase of flight, flexionand extension of the ricoehet, or gallop, which occur in small modem mammals humeral and elbow joints occur; during the propulsive phase (Gambaryan 1967, 1974). On the basis of the functional flexion and extension is repeated (Gambaryan 1974). All analysis and comparisons in the preceding sections, we ten these movements take place in the same plane, and the tatively suggest that in the studied Asian multituberculates parallel position of the axes of the humeral and elbow joints the gait, when theywere moving fast, was most similar to that is most favorable. In mammals with abducted limbs (e.g., of small extantmammals such as, e.g., Meriones (Gambaryan monotrernes)the movements in the humeral joint occur in 1974; Gambaryan et al. 1978); the important difference was FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 83
that the trajectory of the multituberculate jump was prob • Radial and ulnar condyles (no trochlea).
ably much steeper than in any modem small mammal. • Entepicondylar fo ramen. Abducted limbs and steep jumps limited multituberculate • Strong degree of twisting. endurance fo r prolonged run. Pelvis
• Large iliosacral angle. Plesiomorphies and apomorphies of multituberculates Hind limbs • Abducted. It is beyond the scope of this paper to provide a cladistic analysis of early mammals. However, the preceding com Tibia parisons of the skeleton of multituberculates with those of cynodontsand both non-therian and therian mammals, as • Mediolateral diameter greater than craniocaudal. weU as the functional analysis, permit identification of plesiomorphic and apomorphic character states for multitu berculates. This discussion also draws on previously pub lished studies on the postcranial skeleton of multitubercu Synapomorphies lates (Granger & Simpson 1929; Krause & Jenkins 1983; Ve rtebral column Szalay 1993; Sereno & McKenna 1990), as weU as on studies on the postcranial skeleton ofcynodonts and early mammals • Axis with a weU developed dens. Shared with tritylo (Kiihne 1956; Jenkins 1970b, 1971a; Jenkins & Parrington dontids and all mammals. 1976; Sues 1985; Kemp 1980, 1982, 1983) and many others cited in the references. Ribcage
• Ossified stemebrae. Shared with tritylodontids and all Plesiomorphies mammals.
Ve rtebral column Shoulder girdle • Lack of the transverse fo ramen in atlas. • Cervical ribs. • Scapulocoracoid with an incipient supraspinous fo ssa. • Lumbar vertebrae without anapophyses. Kiihne (1986, Shared with Cynognathus (Gregory & Camp 1918) and Text-Fig. 45D) figuredthe apparent anapophyses on the tritylodontids (Kiihne 1956, Fig. 52B), but lacking in lumbar vertebrae in Oligokyphus, but Sues (1985, and Liassic triconodonts (Jenkins & Parrington 1976). personal communication, March 1994) believes that • Procoracoid lacking. Shared with therians. In tritylo they are lacking in tritylodontids. Jenkins (1970b, p. 235 dontids and triconodonts the procoracoid is reduced in wrote): 'Cynodont vertebrae typically bear anapophyses, respect to cynodonts, but still present (Kiihne 1956; short processes which represent the attachment of Jenkins 1970b; Jenkins& Parrington 1976; Sues 1985). longissimus fascicles and which are common only in • Prominent acromion. Shared with tritylodontids and all mammals'. Sues (1985) pointed out that the anapo mammals, although in multituberculates and therians it physes are present in most, but not in allcynodonts. is more prominent than in other mammals (Kiihne 1956; Jenkins & Parrington 1976; Kemp 1983; and per Pectoral girdle sonal observations).
• Interclavicle and clavicle. Humerus
• Lack of ectepicondylar fo ramen. Shared with tritylo Forelimbs dontids and all mammals, but not with the monotremes. • Abducted. Jenkins (1970b, p. 238) stated that: 'There are basic similarities between a cynodont and monotreme hu merus, fo r both retain large ect- and entepicondylar Humerus fo ramina'; however, we have not found the ectepicon
• Teres tuberosity crescent-shaped. dylar foramen in Ornithorhynchus. 84 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
Ulna Femur
• High, compressed olecranon proeess. Shared with trity • Lesser trochanter plate-like, convex lateroproximally, lodontids and all mammals. concave mediodistally and strongly protruding ven trally. • Posttrochanteric fossa. Pelvis • Subtrochanteric tuberde.
• Ilium rod-like, strongly elongated anteriorly, with a longitudinal ridge on the lateral side. Shared with tritylo Tibia dontids and all mammals. • • Acetabulum open dorsocaudally. Shared with tritylo Hook-like proximolateral proeess. dontids, triconodonts, some arboreal (gliding) marsupi als and some swimming eutherians (Desmana). Fibula • Lack of the posterior pro cess of ilium. Shared with trity lodontids and all mammals. • Hook-like proximolateral pro cess. • Epipubic bones. Shared with tritylodontids, mono trernes, marsupials, possibly with earliest eutherians, Ankle joint unknown in triconodonts. • Calcaneum with a deep peroneal groove. • Peroneal tuberde dearly set offfrom the calcaneal body. Femur • Mediodistal calcaneocuboid facet. • Calcaneo-Mt V contact. • Head spherical, on a constricted neck, set apart fromthe • Astragalar canal (sulcus) surrounded by arched buttress shaft. Shared with therians. (Szalay 1993). • Greater trochanter prominent, separated fromthe head • Astragalonavicular joint saddle-shaped. by a deep incisure. Shared with therians. • Abduction-adduction at the astragalonavicular joint, in a horizontal plane, around vertical axis. Kn ee joint The above synopsis, although it does not indude the fo rmal • Patella. Shared with monotrernes and therians, un analysis of the distribution of character states, shows that known in triconodonts, apparently absent in tritylo there are ten postcranial skeleton synapomorphies shared by dontids (Hans-Dieter Sues - personal communication, multituberculates and tritylodontids, the majority of which March 1994). is also shared with all or some other mammals (see, however, • Parafibula. Shared with most marsupials (Haines 1942). Sues 1985 for criticism of tritylodontid-mammal relation ships). Our synopsis do es not support the condusion of Rowe & Greenwald (1987) and Rowe (1988, 1993) on the Ankle joint dose relationships of multituberculates and therians.
• Calcaneal tuberde high, laterally compressed. Shared Rowe's definition of mammals has been criticized by with therians. Lucas (1990), Miao (1991) and Lucas & Luo (1993), while Wible (1991) and Miao (1993) challenged his cranial charac ter analysis. To this criticism, with which we agree, we would like to add comments on the postcranial skeleton. Rowe (1988) recognized twenty postcranial-skeleton synapomor Autapomorphies: phies of the Theria and Multituberculata. We have fo und in Scapulocoracoid the postcranial skeleton only fo ur therian and multitubercu late synapomorphies: procoracoid laeking; femoral head • Coracoid developed as a small proeess on the ventral spherical, placed on a constricted neck, set apart from the angle of the scapula and not bent medially as in therians. shaft;greater trochanter prominent, separated from the head by a deep incisure, and high, laterally compressed, calcaneal Pelvis tuberde. It seems that all of these characters developed independently in multituberculates and therians. • Very small ischial are, placed high dorsally. We give the list of eighteen autapomorphies that distin
• Ischial tuber process-like. guish the multituberculate postcranial skeleton fromth ose • Postobturator fo ramen (or notch). of all other mammals and cynodonts.It is, however, interest • Long ischiopubic symphysis, with ventral keel. ing that recent thorough analyses of the cranial structure of • Iliosacral contact dorsoventral. early mammals by Wible (1991), Wible & Hopson (1993), FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 85
Hopson & Rougier (1993), Rougier et al. (1993) and Lucas & rower, a conclusion corroborated independently by Kielan Luo (1993) place the multituberculates closer to other mam Jaworowska & Qi (1989). mals than the data fromthe postcranial skeleton do. One of The fo regoing analysis of the postcranial anatomy of Late the reasons may be that the braincase is more conservative Cretaceous multituberculates fromthe Gobi Desert does not than the postcranial skeleton and does not change easilywith indicate arboreal habits fo r the studied fo rms. We believe demands of the environment. that the habits of the multituberculates we studied were Another reason is that the characters cited by us as multi similar to those ofmodern murid rodents -jirds (known also tuberculate autapomorphies were fo und in the Late Creta as gerbils), in spite of notable, and sometimes even dramatic ceous and Early Tertiary multituberculates. As the postcra differences in anatomy of multituberculates and placentals nial skeletons of the Late Triassic, Jurassic and Early in general. We have investigated, for comparative purposes, Cretaceous multituberculates are not known, it cannot be the musculature of two representatives of jirds Meriones shown atwhich moment in multituberculate evolution these tamariscinus and Meriones blackleri, both of which live in characters made their appearance. However, one can specu semi-desert regions of northem Caucasus and Armenia, late that the multituberculate ankle joint could have devel respectively. Meriones species studied by us are approxi oped from that of cynodonts (Jenkins 1971a), from which mately of Nemegtbaatar size. Although we have fo und that the Liassic triconodonts and therians can also be derived. Nemegtbaatar and Meriones solved anatomical adaptations These three mammal groups 'solved' the problems of func in a different way, their life-styles may have been compa tional anatomy each in its ownway, and therefore it seems rable. Nowak & Paradiso (1983, p. 652) stated: 'Jirds inhabit reasonable to presume that the functional adaptations clay and sandy deserts, bush country, and steppes, low plains, unique to multituberculates were established at the begin cultivated fields,grasslands and mountain valleys. They are ning oftheir evolution. Our data agree with the conclusion of terrestrial and construct burrows, where they spend much of McKenna (1987) and Miao (1993) that multituberculates their time.' Meriones species are nocturnal, which might have are a sister gro up to all the other mammals. also been the case with studied multituberculates. We agree with Jerison (1973), Crompton etal. (1978) andmanyothers that Mesozoic mammals were night dwellers (Fig. 61). Krause (1986) provided measurements oforbit size relative to skull size for two North American multituberculate spe Habits and extinction cies and argued that the multituberculates studied by him had eyes that were smaller than those of small-eyed, noctur The habits of multituberculates have fascinated paleontolo nal living mammals. Krause (1986, p. 106) stated: 'Interest gists since their discovery in the middle of the 19th century. ingly, while the eyes of Ptilodus are relatively small fo r living Because of the superficial similarity of the lower jaw and the mammals, the olfactory bulbs are relatively the largest dentition pattern to rodents, they have been occasionally (Simpson, 1937; Jerison, 1973), suggestingthat olfaction was referred to as the rodents of the Mesozoic and generally indeed a dominant sense, more so than vision.' He con regarded as the first mammals that occupied herbivorous cluded (contra Landry 1976) that multituberculates prob niches. Krause (1982) reviewed the literature on multituber ably were nocturnal. culate diets and on the basis of a detailed analysis of their In all Late Cretaceous Asian multituberculates studied by dental function argued that they were omnivorous. As we us, the postorbital process is placed far posteriorly on the have not investigated masticatory musculature in this paper parietal (not on the frontalas in therian mammals), indicat (see Wall & Krause 1992 fo r biomechanical analysis of mas ing the presence ofbig eyes. We argue elsewhere (Gambar ticatory apparatus in Ptilodus), we shall not discuss the prob yan & Kielan-Jaworowska, in preparation) that the recog lem of multituberculate diet further. nition of small eyes by Krause (1986) in Ptilodus and As far as locomotion is concerned, Gidley (1909) sug Ectypodus was based on incorrect reconstructions of the gested that Paleocene Ptilodusmight have been saltatorial, position of the postorbital process (on the frontal) in these Simpson (1926) suggested a possibility of semi-arboreal genera by Simpson (1937) and Sloan (1979). The presence of mode oflife fo r multituberculates, and Simpson & Elftman big eyes provides additional support to the idea of the noc (1928, p. 18) stated: 'The pelvic musculature, in agreement turnal mo de oflife of multituberculates. with all other known anatomical and environmental fea We speculate that, similarly to Meriones, Asian multitu tures, indicates an arboreal mode of life [of? Eucosmodon]'. berculates inhabited semi-deserts. Our conclusions are The question was further explored by Jenkins & Krause based in part on the sedimentological evidence. Jerzykiewicz (1983) and Krause & Jenkins (1983), who argued that Pale (1989) and Jerzykiewicz et al. (1994) argued that the dino ocene Ptilodus and ?Eucosmodon were arboreal and con saur eggs, skeletons ofdinosaurs, lizards, mammals and birds cluded (p. 243) that 'some multituberculates, at least, were fo und in the Gobi Desert Djadokhta formation were buried arboreal in habit'. Miao (1988) suggested that Paleocene in eolian sand. Kielan-J aworowska (1977) claimed that there Eocene Lambdopsalis from China might have been a bur- are no remnants of trees in the Djadokhta and Barun Goyot 86 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994)
fo rmations, although tree trunks are common in sandy through an arboreal phase (contra Dollo 1899; Bensley dinosaur-bearing sediments of the younger Nemegt Forma 1901a, 190 1b; Matthew 1904; Lewis 1964, 1989; Steiner 1965; tion, in which mammals have not been fo und. She con Martin 1968; Rowe & Greenwald 1987; and many others; cluded that Late Cretaceous mammals of the Djadokhtaand and in agreement with Gidley 1919; Haines 1958; Kielan Barun Goyot formations were living in steppe or semi-desert Jaworowska 1977; Szalay 1984; and (implicitly) with Napier habitats. She also demonstrated that the two eutherian gen 1961; Altner 1971; and Jenkins 1974). era Kennalestes and Asioryctesfo und together with the mul The problem of multituberculate extinction has been tituberculates studied here had non-opposable pollex and thoroughly reviewed by Van Valen & Sloan (1966) who hallux and certainly were not arboreal. The same holds for concluded that first condylarths, then primates, and finally the somewhat larger eutherian genera Zalambdalestes and rodents contributed to the gradual extinction of multituber Barunlestes from the Djadokhta and Barun Goyot forma culates. Hopson (1967) discussed the competitive inferiority tions, respectively. These were compared in their habits to of multituberculates to placental herbivores in the early modem African Macroscelididae (Kielan-Jaworowska Tertiary. Krause & Jenkins (1983, p. 244) stated: 'However 1978), which also inhabit semi-desert regions. attractive is Hopson's hypothesis, our review of postcranial Asian Late Cretaceous multituberculate genera do not skeleton of North American forms provides no evidence of show unequivocal fo ssorial adaptation, although a possibil features that might be considered significantly inferior to ity of such adaptations has been suggested for an unidenti those of eutherians'. Krause (1986) reviewed the problem of fiedtaeniolabidoid fromthe Djadokhta Formation (Kielan competitive exclusion and taxonomic displacement in the Jaworowska 1989). Paleocene and Eocene mammal communities in North The structure of the pes of Asian multituberculates and America. He demonstrated inverse correlations in generic ?Eucosmodon (and possibly also Ptilodus, which was not diversity and relative abundance between multituberculates studied by us) indicates differences in life-styles. Some ofthe and rodents in the Paleocene and Eocene of the Westem characters of the ? Eucosmodon pes, such as the high mobility Interior of North America. He argued that the sudden ap of the tarsal joints, point to a scansorial mode of life, while pearance of paramyid rodents (which apparently originated others, such as relatively short fo urth and fifth digits, gracile in Asia) in earliest Clarforkian (latest Paleocene) deposits of first metatarsal and wide, not laterally compressed ungual North America (Gingerich & Rose 1977; Rose 1980, 1981) phalanges, speak against it. If? Eucosmodon and other Paleo may have caused major restructuring of early Cenozoic cene multituberculates were indeed scansorial, they must mammal communities in North America, and that competi have solved the adaptation to life in the trees somewhat tive exclusion may have played a role in the decline of differentlythan most modem mammals do. multituberculates. We speculated under 'Functional anatomy' that the re We agree with Hopson (1967) and Krause (1986). Al duction ofthe coracoid to ok place in multituberculates as an though we are aware of the objection of Krause (1986) that adaptation for running with asymmetricalju mping. In the competitive inferiority in terms of individual anatomical evolution of mammals the coracoid became reduced inde features cannot be demonstrated in the fossil record, we pendently at least two (but possibly more) times: in multitu speculate that the structure of the pelvis and limb abduction berculates and in the common ancestor of marsupials and may indicate competitive inferiority of multituberculates to eutherians. We do not know whether it was reduced in the placentals. As demonstrated by Kielan-Jaworowska (1979), evolution of the triconodonts. In Liassic triconodonts, as the pelvis of the multituberculate Kryptobaatar shows a demonstrated by Jenkins & Parrington (1976), the coracoid unique structure characterized by the complete fusionof the is relatively large, similar to that in cynodonts. The coracoid opposite pub es and ischia that form a ventral keel. We regard has not been preserved in the Early Cretaceous triconodont the ventral keel as a multituberculate autapomorphy. Gobiconodon, but the scapulae attributed to this taxon have a Kielan-Jaworowska (1979) argued that because of a very very large supraspinous fo ssa, similar to that in therians, small ischial arc and a long immobile symphysis, the space which indicates a reduction of the coracoid (Jenkins & Schaff available for the passage of an egg in Kryptobaatarwould be 1988, Fig. 13). Likewise, the coracoid has not been preserved less than 3.4 mm, which would be smaller than any known in the only known postcranial skeleton of a docodont cleidoic egg (it would be still notably smaller in Chulsanbaa (Krusat 1991). The coracoid is reduced in an eupantotherian tar). She concluded that multituberculates were bom vivipa fromthe Late Jurassic of Portugal (Krebs 1991), and this may ro us with an extremely small neonate. indicate that it was reduced in the common ancestor of Lillegraven (1975, 1979) argued that the appearance ofthe marsupials and eutherians. We suggest that each time the trophoblast and the ensuing prolongation of the gestation coracoid became reduced, it was as an adaptation for asym period had an enormous impact on the adaptative potential metrical jumping. If this is true, all of the mammals with ityof eutherians. He stated (1979, p. 273): 'I believe that the reduced coracoids must have gone through a stage of the gait extensive development of the eutherian trophoblastic func with asymmetrical jumping. Therefore we believe that the tion was unique and perhaps the single most important post ancestors of mammals with a reduced coracoid did not pass Jurassic event within the Mammalia. It allowed the eutheri- FOSSILS AND STRATA 36 (1994) Anatomy and habits of multituberculates 87
Fig. 61. Reconstruction of Nemegtbaatar. Drawing by Bogdan Bocianowski.
ans to develop precocial young, enter new habitats, fo ster evolution (in some dinosaurs, running birds, different advanced societal behavior and ultirnatelymake possible the hoofed mammals and others) and has always been associated evolution of culture and the historical record. Whole new with the upright limb posture. In multituberculates, because realms of adaptation and behavior not possible within the of the abducted limbs, the mechanics of jumps was very marsupials became realitywithin the Eutheria because ofthis different from that in therian mammals. They apparently breakthrough in reproductive biology.' It is obvious that the were able to run fast on short distances, using asymmetrical extremely narrow pelvis and immobile symphysis of multi gaits with steep jumps, when passing open areas between the tuberculates precluded such evolutionary prospects. bushy parts of the semi-desert, but their endurance for Another character implying competitive inferiority of running prolonged distances was limited. It is also possible multituberculates to eutherians may be the abducted posi that they moved relatively slowly, using symmetrical gaits, tion of their limbs. The sprawling stance, as argued by Rew when seeking food in bushes around their burrows, as castle (1981), is not adaptive for large and cursorial tetra Meriones and many other small modem mammals also do pods: 'The shiftto erect stance occurred in small tetrapods, (Gambaryan 1974). initially as a cursorial adaptation, but also providing the We argued above that the keel in the multituberculate possibility for dramatic size increase' (Rewcastle 1981, p. pelvis might have been developed as a response to the origin 262). Cursorial gait developed several times in tetrapod of femoral adductors ventral to the acetabulum; this in turn 88 Zofia Kielan-Jaworowska & Petr P. Gambaryan FOSSILS AND STRATA 36 (1994) was related to the abducted position of the hind limbs. 1fthis Clemens, W.A., Jr. 1963: Fossil mammals of the type Lance Formation, is true, one may speculate that the abducted position of Wyoming. Part I. Introduction and Multiuberculata. 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Membres et Ceintures des Vertebres Tetrapodes. 710 pp. Zug, G.R. 1972: Anuran locomotion: structure and function.1. Preliminary Librairie Octave Doin, Paris. observations on relation between jumping and osteometrics of ap pen Wall, e.E. & Krause, W.O. 1992: A biomechanical analysis of the mastica- dicular and postaxial akeleton. Copeia 1972, 613-624. ) I Instructions to authors Consult the editor at an early stage regarding suitability of topic, technical Illustrations requirements, and financing. Final acceptance for publication, however, will not be made until the manuscript has been refereed. Illustrations may be either figures in the text or plates fo llowing the text. Plan the figuresso that they take up either the entire width of the type area (170 mm) or the width of one column (80 mm). If an intermediate width Text has to be used, do not exceed 120 mm. Maximum height is 233 mm. 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