DOI: 10.15468/6s9t8g
title: Glires (Mammalia) from the Late Paleocene Bayan Ulan Locality of Inner Mongolia

description: This dataset contains the digitized treatments in Plazi based on the original journal article MENG, JIN, WYSS, ANDRÉ R., HU, YAOMING, WANG, YUANQING, BOWEN, GABRIEL J., KOCH, PAUL L. (2005): Glires (Mammalia) from the Late Paleocene Bayan Ulan Locality of Inner Mongolia. American Museum Novitates 3473: 1-26, DOI: 10.1206/0003-0082(2005)473[0001:GMFTLP]2.0.CO;2, URL: http://www.bioone.org/doi/abs/10.1206/0003-0082%282005%29473%5B0001%3AGMFTLP%5D2.0.CO%3B2ABSTRACTTwo new early diverging members of Glires, Eomylus bayanulanensis, n.sp. and Palaeomylus lii, n.gen. and n.sp., are described from the late Paleocene Bayan Ulan Fauna, Inner Mongolia, China. These species add significantly to the diversity of Glires known from the early Paleogene of Asia. E. bayanulanensis and Palaeomylus sp. come from the lowest level of the Bayan Ulan section, from which the classic Bayan Ulan Fauna was collected. Palaeomylus lii and specimens belonging to two other genera of mammals, Pseudictops and Palaeostylops, are found from a horizon about 8 m above strata yielding the Bayan Ulan Fauna. These taxa are tentatively regarded as constituting a distinct faunal assemblage, which may prove to be of biostratigraphic utility within the region. Two calcanea tentatively assigned to Gomphos from a stratigraphic horizon slightly above the bed producing P. lii suggest the presence of strata of Early Eocene age in the Bayan Ulan section.INTRODUCTIONPaleontological investigation in the Bayan Ulan area traces back to the 1920s, when a field party of the Central Asiatic Expeditions (CAE) of the American Museum of Natural History visited the Nom Khong Shireh of Inner Mongolia while making its way northeast from Shara Murun to Erlian. Nom Khong Shireh (also known as Nomogen today, meaning‘ ‘holy’’) is an isolated mesa in the middle of a vast basin (see Meng et al., 1998, for a review of the research history). The Bayan Ulan Fauna was discovered at the northern foot of the mesa several decades later. First reported by Qi (1979), the fauna has recently been described (Meng et al., 1998). Fossils from Bayan Ulan have figured in numerous other recent studies (Miao, 1988; Meng, 1992; Meng et al., 1994, 1998; Meng and Wyss, 1994, 1995, 1997, 2001; Meng and McKenna, 1998). Current consensus places the Bayan Ulan Fauna in the late Paleocene Gashatan Asian Land Mammal Age, making it one of the earliest Tertiary mammal faunas known from the Mongolian Plateau (Meng et al., 1998; Meng and McKenna, 1998; Ting, 1998).1 Division of Paleontology, American Museum of Natural History (jmeng@amnh.org).2 Department of Geological Sciences, University of California, Santa Barbara, CA, 93106 (wyss@geol.ucsb.edu).3 Division of Paleontology, American Museum of Natural History (yhu@amnh.org); Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences; Biology Program (EEB), Graduate School and City College, City University of New York.4 Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, P.O. Box 643, Beijing 100044, P.R. China (wang.yuanqing@pa.ivpp.ac.cn).5 Department of Earth Sciences, University of California, Santa Cruz, CA 95064 (pkoch@es.ucsc.edu).6 Biology Department, University of Utah, Salt Lake City, UT 84112 (gbowen@biology.utah.edu).Early diverging members of Glires are known primarily from Paleocene and Eocene localities of Asia, Bayan Ulan included. Many of these forms are commonly termed eurymylids (or eurymyloids) and mimotonids. Eurymylids are regarded as those members of Glires, exclusive of rodents, characterized by having one pair of enlarged incisors in the lower and upper jaws. This concept changed recently with the discovery of a eurymylid taxon, Sinomylus, which has two pairs of lower and one pair of upper incisors (Kondrashov and Lopatin, 2003; Lopatin and Kondrashow, 2003). Mimotonids are generally regarded as those members of Glires, exclusive of Lagomorpha, having two pairs of incisors in both the upper and lower jaws. Eurymylids and mimotonids are quite diverse in the Paleogene of Asia and are pivotal to understanding the origin of rodents and lagomorphs on the continent. In addition, these fossils are useful in biostratigraphic correlations across the region because of their restricted stratigraphic distribution and distinctive morphology.Since Russell and Zhai’s (1987) compilation of the Bayan Ulan Fauna, additional collecting has been carried out at the locality, primarily by Meng and Wyss during field seasons in 1987 and 1992–1995. This work yielded several new taxa and additional material of previously known taxa, most of which have been published (Meng et al., 1998). Three taxa of Glires have been previously reported from Bayan Ulan: Eomylus borealis,? Khaychina elongata, and Tribosphenomys minutus, of which only T. minutus has been described in detail (Meng et al., 1994; Meng and Wyss, 1994, 2001). Efforts to understand the fauna and the stratigraphic sequence hosting it have been continuously made, particularly in the context of exploring biotic and environmental changes across the Paleocene–Eocene boundary (Bowen et al., 2003, 2005). This interval coincides with a critical period of global warming and the first appearances of several major modern clades of eutherian mammals in the evolutionary history of mammals (Koch et al., 1992; Bowen et al., 2001, 2002). New specimens were collected from the Bayan Ulan locality in 2002–2004. In addition to those pertaining to the classic Bayan Ulan Fauna, a small sample of fossils was collected from a stratigraphic horizon 8 m above the one containing the typical Bayan Ulan Fauna. As these specimens are associated with precise stratigraphic and paleomagnetic data, they enhance understanding of the biostratigraphy at Bayan Ulan considerably (Bowen et al., 2005). Herein we describe the specimens of Glires from Bayan Ulan section, except Tribosphenomys, and briefly comment on current controversies regarding their phylogenetic relationships and taxonomy as well as their biochronologic implications.