The first record of the late Miocene Hyaenictitherium hyaenoides Zdansky (Carnivora: Hyaenidae) in Inner Mongolia and an evaluation of the genus

ABSTRACT

New dental material of the hyaenid Hyaenictitherium hyaenoides Zdansky, 1924 from the late Miocene Baogeda Ula Formation in central Inner Mongolia is described. An evaluation of the morphological trends and spatial and temporal ranges of the genus Hyaenictitherium follows. The unworn isolated teeth described here represent a nearly complete set of dentition. Furthermore, the Baogeda Ula material is the eastern-most record of this genus, and the only hyaenid record in eastern Asia associated with a layer of basalt capping the fossil producing sediments. Previous studies of the capping basalt and associated small mammal fauna constrain the age of the Baogeda Ula hyaenid at 8–7 Ma. In addition to the Baogeda Ula material, other occurrences of the genus in eastern Asia include Gansu, Shanxi and Shaanxi provinces of northern China. Of the ten species currently thought to belong to the genus, two (H. intuberculatum and H. minimum) appear more primitive than the others. The rest seem to follow a morphological trend of increasing size and robustness of the teeth, as well as reduction of the trigonid of m1. This trend is observed roughly from H. wongi (MN9) to H. namaquensis (MN14). The genus appears to be a cursorial form and first appeared in western Eurasia in MN9. Subsequent range expansion occurred in northern Asia, southern Asia, and in Africa from MN12 on. The observed phylogenetic and morphological gaps between H. namaquensis and H. minimum prevent a clear interpretation of Hyaenictitherium immigration into Africa.