title: New Early Eocene basal tapiromorph from southern China and its phylogenetic implications.
abstract: A new Early Eocene tapiromorph, Meridiolophus expansus gen. et sp. nov., from the Sanshui Basin, Guangdong Province, China, is described and discussed. It is the first reported Eocene mammal from the basin. The new taxon, represented by a left fragmentary mandible, is characterized by an expanded anterior symphyseal region, a long diastema between c1 and p1, a rather short diastema between p1 and p2, smaller premolars relative to molars, an incipient metaconid appressed to the protoconid on p3, a prominent entoconid on p4, molar metaconid not twinned, cristid obliqua extending mesially and slightly lingually from the hypoconid, inclined metalophid and hypolophid, and small hypoconulid on the lower preultimate molars. Meridiolophus is morphologically intermediate between basal Homogalax-like taxa and derived tapiromorphs (such as Heptodon). Phylogenetic analysis indicates Equidae is more closely related to Tapiromorpha than to Palaeotheriidae, although the latter is only represented by a single species Pachynolophus eulaliensis. 'Isectolophidae', with exception of Meridiolophus and Karagalax, has the closest affinity with Chalicotherioidea. Furthermore, the majority rule consensus tree shows that Meridiolophus is closer to Karagalax than to any other 'isectolophid', and both genera represent stem taxa to crown group Ceratomorpha.
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China; Division of Paleontology, American Museum of Natural History, New York, New York, United States of America.
authors.forename: Bin
authors.initials: B
authors.lastname: Bai
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Yuanqing
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Division of Paleontology, American Museum of Natural History, New York, New York, United States of America; Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Meng
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Xun
authors.initials: X
authors.lastname: Jin
mesh_terms: D000818:Animals; D002681:China; D005580:Fossils / Q000033:anatomy & histology*; D008334:Mandible / Q000033:anatomy & histology*; D010527:Perissodactyla / Q000033:anatomy & histology / Q000145:classification*; D010802:Phylogeny