title: Earliest known unequivocal rhinocerotoid sheds new light on the origin of Giant Rhinos and phylogeny of early rhinocerotoids.
abstract: Forstercooperiines are a group of primitive rhinocerotoids with a relatively large body size in the Eocene, and normally considered to be closely related to Giant Rhinos. Here we report a new forstercooperiine, Pappaceras meiomenus sp. nov., from the late Early Eocene Arshanto Formation, Erlian Basin, Nei Mongol, China. Pappaceras is the earliest known unequivocal rhinocerotoid, and the holotype of the new species, represented by the most complete cranium of forstercooperiines known to date, shows the earliest evidence of reduction of the first upper premolar in rhinocerotoids, and resembles paraceratheriine Juxia in basicranial features, supporting the interpretation that the forstercooperiine clade is ancestral to paraceratheriines. The new species also displays some similarities with amynodontids in craniodental structures. Phylogenetic analysis identifies P. meiomenus as a basal taxon of the monophyletic forstercooperiines. It also reveals novel phylogenetic relationships of early rhinocerotoids that indicates Uintaceras is the sister group of paraceratheriids, to which amynodontids are more closely related than to any other group of rhinocerotoids. Furthermore, the eggysodontid clade is excluded from hyracodontids and placed as the sister group of rhinocerotids. Hyracodontidae, excluding paraceratheriids and eggysodontids, is placed as the most basal group of the rhinocerotoids.
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, 100044, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Haibing
authors.initials: H
authors.lastname: Wang
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, 100044, China.
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, 100044, China.|Division of Paleontology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA.
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, 100044, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Yuanqing
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D002681:China; D005580:Fossils; D005843:Geography; D005844:Geology; D007568:Jaw; D010163:Paleontology; D010527:Perissodactyla / Q000502:physiology*; D010802:Phylogeny; D012886:Skull