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The First Haramiyoid Mammal from Asia

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The First Haramiyoid Mammal from Asia Naturwissenschaften (2005) 92:40–44 DOI 10.1007/s00114-004-0584-y SHORT COMMUNICATION Michael W. Maisch · Andreas T. Matzke · Franziska Grossmann · Henrik Sthr · Hans-Ulrich Pfretzschner · Ge Sun The first haramiyoid mammal from Asia Received: 11 August 2004 / Accepted: 6 October 2004 / Published online: 9 November 2004 Springer-Verlag 2004 Abstract A lower molar of a haramiyoid mammal is 1996) have become available. The record of the described from the Toutunhe Formation of Liuhuanggou Haramiyida was also considerably extended through the near Urumqi in the southern Junggar Basin, Xinjiang, discoveries of Eleutherodon oxfordensis in the Middle China. It is referred to Eleutherodon sp., otherwise ex- Jurassic (Bathonian) of England (Kermack et al. 1998; clusively known from the Upper Bathonian of England. It originally not assigned to the Haramiyida, which was is the first record of the order Haramiyida from Asia and done by Butler 2000), and Staffia aenigmatica, the latest the first Mesozoic mammal described from the southern known haramiyid, from the Upper Jurassic (Kimmerid- Junggar Basin. Apart from the English specimens of gian) of Tendaguru in East Africa (Heinrich 1999), which Eleutherodon and Staffia from the Upper Jurassic of East also represents the first record from Gondwana. Africa, it is the geologically youngest haramiyoid known. Here we report a well-preserved left lower molar from It is the first vertebrate taxon from the Toutunhe For- the late Middle Jurassic (Bathonian-Callovian, according mation that is probably not endemic and lends some to Eberth et al. 2001, but see discussion below) Toutunhe support to the dating of the Formation as late Middle Formation of the southern Junggar Basin that is referable Jurassic, probably Bathonian. to E. oxfordensis. The specimen was discovered in a bonebed close to the top of the Toutunhe Formation (14.75 m below the overlying Qigu Formation) in the Introduction Liuhuanggou gorge, about 40 km southwest of Urumqi in the Xinjiang Uygur Autonomous Region, People’s Re- Among the rare and enigmatic groups of Mesozoic public of China. The bonebed yielded numerous isolated mammals, the basal allotherians (Marsh 1880) of the or- remains of osteichthyan and chondrichthyan fish, tem- der Haramiyida (systematics here follows the overview of nospondyl amphibians and reptiles, as well as several Butler 2000) are particularly little known. Even their mammalian teeth, most of which are referable to a new status as mammals is questionable, as the most inclusive genus and species of docodont with pseudotribosphenic recent analysis of Mesozoic mammal phylogeny (Luo et molars that will be described elsewhere (Pfretzschner al. 2002) places them either as a sister group of trity- 2003). On top of the bonebed there is a layer rich in lodontids (non-mammalian cynodonts) or the mammalian larger, isolated bones of fish, amphibians, and reptiles that multituberculates. Until recently, only the typical, multi- has been termed the turtle–archosaur–amphibian assem- tuberculate-like teeth were recorded from several Upper blage by Maisch et al. (2001, 2003), from which tem- Triassic and Lower Jurassic occurrences in Western and nospondyl amphibians (Maisch and Matzke 2004; Maisch Central Europe (Hahn 1973; Hahn et al. 1989; Sigogneau- et al. 2004), theropod dinosaurs (Maisch and Matzke Russell 1989; Butler and MacIntyre 1994). With the re- 2003), rhamphoryhnchoid pterosaurs, goniopholidid cro- cent discovery of Haramiyavia clemmenseni in Upper codiles, shark remains, and, particularly, xinjiangchelyid Triassic rocks of Greenland (Jenkins et al. 1997), asso- turtles are known. ciated cranial and even post-cranial remains (Amaral M. W. Maisch ()) · A. T. Matzke · F. Grossmann · H. Sthr · Systematic palaeontology H.-U. Pfretzschner Institut und Museum fr Geologie und Palontologie, Infraclass Allotheria Marsh, 1880 Sigwartstr. 10, 72076 Tbingen, Germany e-mail: [email protected] Order Haramiyida Hahn, Sigogneau-Russell and Wouters, 1989 G. Sun Suborder Haramiyoidea Hahn, 1973 Research Center of Paleontology, Family Eleutherodontidae Kermack, Kermack, Lees, Jilin University, and Mills, 1998 6 Xi-Minzhu Street, 130026 Changchung, China 41 Fig. 1 Left lower molar of the eleutherodontid haramiyid Eleutherodon sp. from the up- permost Toutunhe Formation (late Middle Jurassic, ? Batho- nian) of Liuhuanggou, SW Ur- umqi, Xinjiang, China, in a oc- clusal, b mesial and occlusal, c distal, d lingual, and e buccal view. The labels a1, a2, and b2 indicate the principal cusps. Arrows labelled with m indicate the mesial, with l the lingual direction. Scale bars are 300 mm. Fig 2 Details of SGP 2001/33. a The great occlusal basin wear facet. b Fluted transversal rid- ges on the buccal surfaces of the lingual cusps. Scale bars are 200 mm. Genus Eleutherodon Kermack, Kermack, Lees and Formation) of Liuhuanggou, southwest Urumqi, Xinjiang Mills, 1998 (see Maisch et al. 2003 for further details). Type-species Eleutherodon oxfordensis Kermack, Kermack, Lees and Mills, 1998 Diagnosis: see Kermack et al. 1998 and Butler 2000 Description Eleutherodon sp. Material: SGP1 2001/33 (Figs. 1, 2): an almost com- The specimen (Figs. 1, 2) represents a lower molar, as it plete left lower molar from the uppermost Toutunhe only possesses a buccal and a lingual row of cusps. The Formation (14.75 m below the boundary to the Qigu position of the main mesiobuccal cusp allows identifica- tion as a left lower molar. In occlusal view (Fig. 1a), the crown is ellipsoidal with the mesial end wider than the 1 Sino German Project collection, currently housed at the Univer- distal one, which tapers slightly. The mesial edge of the sity of Tbingen, Germany. The collection remains the property of crown is strongly oblique in the mesiobuccal–distolingual the People’s Republic of China and will be transferred to a public direction due to the strong mesial expansion of the cusp Chinese collection after the scientific studies are finished. The final repository will be announced in an internationally accessible b2, the principal cusp of the buccal row (the homology of journal. the cusps follows Butler 2000 rather than Kermack et al. 42 1998). The buccal and lingual margins of the crown are there are two rows of cusps that are not parallel but gently and evenly convex, as is the distal margin. The two converge distally; the mesial margin of the lower molars rows of cusps are not parallel but converge distinctly is oblique, due to the strong development of the buccal distally. cusp b2; the lower occlusal basin extends for the entire The buccal row presents five cusps (Fig. 1a, b, e). The length of the tooth without an intervening saddle; there is mesial-most is by far the largest and protrudes strongly a strong fluting of the margins of the lower occlusal mesially and occlusally. Its apex curves markedly distally. groove or basin. This cusp is here identified as b2. The following cusp is The only apparent difference to the British material very small, less than one-fifth the size of the b2 cusp and lies in the fact that the Chinese specimen has only five less than one-third of the size of the following cusps. The buccal, and four (or five if the worn distal cusp is counted distal three buccal cusps are again larger and decrease in into this series) lingual cusps. In the British specimens the size and height distally. The distal-most cusp is strongly number of cusps is usually larger. However, the z lower worn or abraded at its apex. It is not clear whether there molar described by Kermack et al. (1998) also has only was a distal cusp connecting the buccal and lingual rows four to five buccal and seven lingual cusps. The b teeth and closing the occlusal basin distally. Certainly there is have 21 and 12 cusps, respectively, so that there appears no cusp remaining, but it appears as if originally one was to be an enormous variation of cusp number in the ma- present that was completely abraded or worn down, as terial attributed to E. oxfordensis. As otherwise the teeth particularly obvious in distal view (Fig. 1c). agree perfectly in morphology, the fact that the Chinese The lingual row (Fig. 1a, b, d) consists of only four specimen has two cusps less than any of the British cusps that are subequal in size. The mesial-most, which specimens does not merit taxonomic distinction. The most probably represents the cusp a1 of other haramiyids, enormous variation in the number of cusps in Eleuther- is much smaller and lower than the cusp b2. The fol- odon might be attributed to different positions of the lowing cusp a2 is even slightly higher than a1. The distal- lower molars in the jaws. It could also be caused by on- most lingual cusp is the lowest in the series. togeny. With the little material presently at hand, this is The entire crown is traversed mesiodistally by a wide impossible to decide. If with a larger sample available the occlusal basin that extends from the mesial to the distal Chinese form should turn out to constantly display fewer margin and occupies more than half the width of the cusps in the lower molars than the British Eleutherodon,a crown (Figs. 1a, 2a). Transverse fluted ridges caused by taxonomic distinction might be warranted. At the mo- wear extend from the margins of the lingual and buccal ment, considering the apparent, although small differ- cusps towards the centre of the basin (Fig. 2a, b). They are ences to the British specimens, we consider it best to refer most prominent on the lingual side of the three disto- the specimen to Eleutherodon sp. buccal cusps and on the buccal sides of the three disto- The other haramiyoid genera differ considerably from lingual cusps (Fig. 2b). There are no clear flutings evident Eleutherodon, and thus from the Chinese specimen.
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