Morphology of an Early Oligocene beaver Propalaeocastor irtyshensis and the status of the genus Propalaeocastor

PeerJ

article

Lüzhou Li¹  Qiang Li¹  Xiaoyu Lu¹  Xijun Ni¹ 

[1] Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences;University of Chinese Academy of Sciences;CAS Center for Excellence in Tibetan Plateau Earth Sciences

关键词: Xinjiang;    Beavers;    Propalaeocastor;    Early Oligocene;    Irtysh River Formation;   

DOI  :  10.7717/peerj.3311

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

The Early to Late Oligocene Propalaeocastor is the earliest known beaver genus from Eurasia. Although many species of this genus have been described, these species are defined based on very fragmentary specimens. Propalaeocastor irtyshensis from the Early Oligocene Irtysh River Formation in northwestern Xinjiang, China is one of the earliest-known members of Propalaeocastor. This species is defined on a single maxillary fragment. We revise the diagnosis of P. irtyshensis and the genus Propalaeocastor, based on newly discovered specimens from the Irtysh River Formation. The dental morphology of P. irtyshensis is very similar to other early castorids. The caudal palatine foramen of P. irtyshensis is situated in the maxillary-palatine suture. This is a feature generally accept as diagnostic character for the castorids. On the other hand, P. irtyshensis has two upper premolars, a rudimentarily developed sciuromorph-like zygomatic plate, and a relatively large protrogomorph-like infraorbital foramen. Some previous researchers suggested that Propalaeocastor is a junior synonym of Steneofiber, while other took it as a valid genus. Our morphological comparison and phylogenetic analysis suggest that Propalaeocastor differs from Steneofiber and is a valid genus. We also suggest that Agnotocastor aubekerovi, A. coloradensis, A. galushai, A. readingi, Oligotheriomys primus, and “Steneofiber aff. dehmi” should be referred to Propalaeocastor. Propalaeocastor is the earliest and most basal beaver. The origin place of Propalaeocastor and castorids is uncertain. The Early Oligocene radiation of castorids probably is propelled by the global climate change during the Eocene-Oligocene transition.

【 授权许可】

CC BY