Abstract

The mammalian fauna of the so-called chalicothere pit, lower Eocene basal Arshanto Formation, Erlian Basin, Inner Mongolia, comprises at least eight species, of which Litolophus gobiensis is the most abundant large mammal, represented by at least 24 individuals and 1252 specimens of skulls, mandibles, and postcranial elements. The Litolophus assemblage is dominated by young adult individuals, while juveniles are under-represented, an age profile that conforms to the theoretical model of a catastrophic assemblage. The assemblage is characterized by skeletal elements with limited weathering and moderate disarticulation, and a paucity of isolated teeth, suggesting that the carcasses were probably exposed to the environment after death for only a brief period. Fluvial activity was prominent and had sufficient energy to align most long bones of Litolophus (∼153.1 kg in mean value) in a NNE-SSW direction. Most elements in the assemblage belong to Voorhies Groups II and/or III, while elements of Group I are rare. In addition, the Litolophus carcasses were evidently disturbed by predators and/or scavengers before burial. Damage to the ends of long bones is unevenly distributed, probably reflecting both preferential feeding behavior by predators or scavengers and the timing of epiphyseal fusion in Litolophus. The scarcity of juvenile individuals can also partially be attributed to predation or scavenging; however, it seems unlikely that the chalicothere pit was a scavenger den.

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