[N] 2006 A peculiar palaeryctid-like mammal from the Maastrichtian of Mongolia
Bolortsetseg, M., Minjin, C. & Geisler, J. (2006) A peculiar palaeryctid-like mammal from the Maastrichtian of Mongolia. JVP 26(3) Abstracts pp.44
Unlike North America, the record of Maastrichtian mammals in Asia is poor. Excluding India, which was separate from Asia at the time, the only definitive Maastrichtian mammal from Asia is an undescribed metatherian skull from Guriliin Tsav, Mongolia. Apossible second record consists of the multituberculate Buginbaatar transaltaiensis, which is known from Mongolian locality of Khaichin-I. The reported fauna of this locality is meager and is consistent with a Late Cretaceous or Paleocene age. In the summer of 2005, we collected additional vertebrate fossils from Khaichin-I. Although the focus of this abstract is the mammal fossils we discovered, we also found fragmentary remains of non-avian theropods, which together with the stratigraphic position of Khaichin-I, establishes the age of this locality as late Maastrichtian.
Our most important discoveries from Khaichin-I are 3 specimens of mammals. The first of these is a partial dentary of the metatherian Deltatheridium pretrituberculare, which was formerly restricted to Campanian age strata from Mongolia and Kazakhstan. The remaining two specimens, including a partial skull, represent a new and unusual species of eutherian mammal. Remarkable features of this species are large “saber-like” upper canines, loss or extreme reduction of lower incisors, and only two lower premolars. Like Cimolestes and Palaeoryctidae, our new taxon has talonids narrower than trigonids, trigonids that tower above the talonids, transversely elongate upper molars, and P4 paracone higher than those on the molars.
Like palaeoryctids, the paracone and metacone on M1 and M2 are twinned and have steep lingual and labial faces. These similarities suggest that our new mammal is
more closely related to Cretaceous and Paleocene taxa from North America than to other Cretaceous, Mongolian, endemic mammals. A similar argument has been put forth for Buginbaatar, thus the late Maastrichtian may have been a period of increased faunal exchange between Asia and North America.