New multituberculate mammals from the Lower Cretaceous (Shahai and Fuxin formations), northeastern China

ABSTRACT

Two eobaatarid multituberculates, Heishanobaatar triangulus gen. et sp. nov. and Eobaataridae gen. et sp. indet., and an ?albionbaatarid multituberculate, Kielanobaatar badaohaoensis gen. et sp. nov., from the Lower Cretaceous (Aptian to Albian) Shahai and Fuxin formations in Liaoning Province, northeastern China, are described. Heishanobaatar triangulus is a moderate-sized multituberculate characterized by lower jaw dental formula 1.0.3.2, slender lower incisor, single-rooted p2, triangular p3 in lateral view, p4 with eight serrations, m1 with cusp formula 2:2, and m2 with cusp formula 1 (coalesced):2. Kielanobaatar badaohaoensis is characterized by upper anterior premolars with relatively flat occlusal surfaces, roughly pentangular P1 in occlusal view, P1 and P2 with three cusp rows (cusp formulae 1:3:2), and P3 with four cusps (cusp formula 2:2). Together with already described three species of eobaatarids from the same localities, they demonstrate that there were quite diverse multituberculates in Asia in the late Early Cretaceous, and suggest that the mammalian fauna known from the Shahai and Fuxin formations probably show a transitional state from the mammalian fauna of the Yixian Formation to Late Cretaceous Asian faunas.

ACKNOWLEDGMENTS

We would like to express our sincere gratitude to Chuankui Li, Shuhua Xie, as well as many other colleagues and technicians of IVPP, Zhenglu Chang (Investigation Team No. 107, Northeast Coalfield Geological Bureau, Fuxin, China), Takehisa Tsubamoto (Hayashibara Biochemical Laboratories, Inc., Okayama, Japan), Takahiro Takada (Gunma University, Maebashi, Japan), and colleagues of Kyoto University, Kyoto, Japan, for their assistance, advice, and support of this study. Specimen observation in Moscow was kindly supported by Evgeny N. Maschenko (Paleontological Institute of the Russian Academy of Sciences, Moscow, Russia). SEM photographs were taken at the Kyoto University Museum with support of Terufumi Ohno, Masahiro Ichida, and Tomohiro Nishimura (Kyoto University). We also thank Brian Davis (Sam Noble Oklahoma Museum of Natural History, Norman, U.S.A.) for English correction. This paper was greatly improved by comments and advice of Gerhard Hahn (Berlin, Germany), another anonymous referee, and an editor, Thomas Martin (Bonn University, Bonn, Germany). This study was partly supported by National Science Fund for Fostering Talents in Basic Research, Special Research Disciplinary Unit (Paleontology and Paleoanthropology), China (J0630965), and Chinese Academy of Sciences Research Fellowship for International Young Researchers.