title: Two New Mylagaulid Rodents from the Early Miocene of China.
abstract: Mylagaulid fossorial rodents are a common component of North American Miocene fossil faunas. However outside of North America, only three species are known from Asia. Here we report two new mylagaulids, Irtyshogaulus minor gen. et sp. nov. and Irtyshogaulus major gen. et sp. nov., recovered from early Miocene sediments in the Junggar Basin in northwestern China. The two new taxa are small-sized, high-crowned promylagauline rodents. Their lower molars possess high metastylid crests, small mesostylids, broad and posterolingually expanded labial inflections, and transversely extending metalophid IIs. The mesoconid is absent in both species. The anterior and posterior fossettids are large and equally developed. Their upper M1-2s possess a square occlusal surface with five deep fossettes. The two new taxa are distinguished from each other mainly by their size, the morphology of fossettes and fossettids, development of mesial and distal lophs, posterior reduction of M3, and the orientation of m2 hypolophid. Our phylogenetic analysis indicates that Irtyshogaulus and Lamugaulus (another early Miocene Asian mylagaulid) are sister taxa. The two genera are nested among the North American promylagaulines, and share a common ancestor from North America, indicating early Miocene intercontinental dispersal within this clade of rodents.
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 142 Xi Zhi Men Wai Street, Beijing, 100044, China.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Lu
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 142 Xi Zhi Men Wai Street, Beijing, 100044, China.|CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, 100101, China.
authors.forename: Xijun
authors.initials: X
authors.lastname: Ni
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 142 Xi Zhi Men Wai Street, Beijing, 100044, China.
authors.forename: Lüzhou
authors.initials: L
authors.lastname: Li
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 142 Xi Zhi Men Wai Street, Beijing, 100044, China.|CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, 100101, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Li
mesh_terms: D000818:Animals; D049628:Body Size; D002681:China; D005580:Fossils; D008964:Molar, Third / Q000033:anatomy & histology*; D010802:Phylogeny; D012377:Rodentia / Q000033:anatomy & histology / Q000145:classification*