Table of Content

15 September 2007, Volume 45 Issue 3

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A New Late Jurassic Docodont (Mammalia) from Northeastern Xinjiang, China

HU Yao-Ming, MENG Jin, James M. CLARK

2007, 45(3):  173-194. 

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A new genus and species of docodontid (Docodonta, Mammalia),Acuodulodon sunae, represented by a partial left lower jaw and dentition, is described. It is from the upper part of the Shishugou Formation in the Wucaiwan area of the Junggar Basin in northeastern Xinjiang, China, with an estimated age of 159~161 Ma (Oxfordian, early Late Jurassic). The new mammal is typical of docodonts in having a cusp b in front of cusp a, a cusp c distolingual to cusp a and a cusp g mesiolingual to cusp a on lower molariforms. Differing from other docodonts, it has no cusp e or crest b–e developed on lower molariforms. Unique among docodonts, cusps a and c of the new animal maintained their sharpness while cusp g and crest b–g wore away fast, indicating that both shearing and crushing/grinding occurred in the chewing cycle and probably last for most of the life span of the animal. Phylogenetic analysis of a data matrix with 24 lower molariform characters across 15 taxa recovers a monophyletic Docodonta, which has distinct diagnostic characters in lower molariforms. Within docodonts, Docodon andBorealestes are successively basal to other docodonts; Acuodulodon andItatodon + (Simpsonodon, Castorocauda + (Tegotherium + Sibirotherium)) form a monophyletic clade. Tegotheriid genera are nested within Docodontidae, but a monophyletic tegotheriid clade composed of Tegotherium,Sibirotherium, Itatodon, and Tashkumyrodon is not recovered. The dentary ofAcuodulodon is typical of docodonts. It has a shallow postdentary trough and a wide and sharp medial ridge, both of which do not extend onto the medial side of the condylar peduncle, indicating looser contact between postdentary bones and the dentary than in morganucodontids, a more derived condition in the evolution toward the definitive mammalian middle ear. 

LATE EOCENE CRICETIDS (RODENTIA, MAMMALIA) FROM NEI MONGOL, CHINA

WANG Ban-Yue

2007, 45(3):  195-212. 

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Among the micromammal fossils collected from the Upper Eocene of Nei Mongol by the teams of IVPP in 1980-1990's(Wang,2001,2007) there were some specimens of cricetids. They represent the first cricetids ever found in Late Eocene of Nei Mongol. The discovery not only has expanded the distribution of these cricetids in Asia, added new genera and species of the cricetids to the local faunas, but also plays an important role in determining the ages of the fossiliferous beds in these localities. The cricetids are described below.

NEW MATERIALS OF SINOHIPPUS FROM GANSU AND NEI MONGOL, CHINA

HOU Su-Kuan, DENG Tao

2007, 45(3):  213-231. 

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New materials of Sinohippus from the Late Miocene"Hipparion Red Clay"of Gansu and Nei Mongol, China, are described and identified as Sinohippus robustus sp. nov.A review of the known specimens of Sinohippus indicates that this genus is generically distinct from other members of Anchitheriinae. The sympatry of the low-crowned Sinohippus with the high-crowned Hipparion indicates that there should have been a small quantity of shrub distributed during the Late Miocene in northern China.

PLIO-PLEISTOCENE SMALL MAMMALS FROM THE NIUTOUSHAN SECTION OF THE YUXIAN BASIN, CHINA

Cai Bao-Quan, Zheng Shao-Hua, Li Qiang

2007, 45(3):  232-245. 

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The Niutoushan (or Pulu) section, which was originally described by Du et al.(1988) as one of the stratotypes in erecting the"Daodi Formation", is located about one kilometer south of Pulu village, Yuxian county, and 1.2 km north of the Danangou section(Cai et al.,2004). Both the Niutoushan and the Danangou sections are on the east side of the highway connecting Xuanhua city to the Yuxian county seat.In addition to the Donggou section near the Qianjiashawa village, the Niutoushan section potentially represents the only other record of the Pliocene/Pleistocene boundary in the Nihewan district, as indicated by the presence of derived Mimomys cf.M. youhenicus. We remeasured the Niutoushan section to develop a more complete profile in 2005. The profile was original 43.18 m measured by Du et al.(1988). As a result of our fieldwork, the profile is now 82 m, with an additional 12 stratigraphic layers (11 to 23)(see Fig.1). Small mammals were collected from Layers 3,6,9,12,15 and 16 by screen-washing(see Table 1). The mammals from each layer represent one faunal complex with some species spanning multiple layers.

A new thalattosaurian (Reptilia: Diapsida) from the Upper Triassic of Guizhou, China

CHENG Yen-Nien, WU Xiao-Chun, SATO Tamaki

2007, 45(3):  246-260. 

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A new thalattosaurian, Miodentosaurus brevis gen. et sp. nov., is established on the basis of the fairly preserved skull and mandible of a skeleton from the Triassic Falang Formation, Guizhou Province. M. brevis is a relatively large thalattosaurian, with a total length of more than 4 m. The very short snout, with a straight profile, is the most striking of the diagnostic characters of the new taxon. Other diagnostic features include the presence of a crest along the anterodorsal midlines of the premaxillae, the edentulous maxilla, the presence of a groove-like trough along with the anterolateral margin of the maxilla on the ventral surface, the presence of six conical premaxillary teeth, and no more than six conical dentary teeth which are restricted to the anterior portion of the dentary. The absence of the vomer and pterygoid teeth, the anterior shift of the large pineal foramen, and the elongation of the neck indicate that M. brevis may have had a close relationship with the Askeptosauroidea, to which the Chinese genus, Anshunsaurusis referred.