Anatomy and Systematics of Notohippus toxodontoides Ameghino 1891 (Mammalia, Notoungulata) from the Miocene of Santa Cruz Province, Argentina

HERNANDEZ DEL PINO, S; FERNÁNDEZ, M.; FERNICOLA, J.C.; CERDEÑO SERRANO, M. E.

JOURNAL OF VERTEBRATE PALEONTOLOGY

SOC VERTEBRATE PALEONTOLOGY

Lugar: Lawrence; Año: 2019

0272-4634

The specimens herein presented come from the Río Bote locality, Santa CruzFormation (early Miocene), Santa Cruz Province, Argentina. They include the most complete cranial material of the ?Notohippidae? Notohippus toxodontoides, and other remains that allow increasing the knowledge on mandible and dentition. The new remains permit the extension of the original description proposed by Ameghino in the XIX century, and provide some data on the ontogenetic variation in the dental traits of this species. Notohippus differs from the Deseadan?Colhuehuapian genus Argyrohippus in the following features: discontinuous dentition; C and p1 absent; shorter P2?M3/p2?m3 series; crown of I1 highly curved; upper molars with less developed parastyle and paracone fold, less undulate ectoloph, deeper distolingual groove of M3 directed more lingually, and presence of a very shallow distolabial groove; incisiviform lower canine; and lower molars with posterolabial angle of the talonid more rounded, and narrowertrigonid valley. As stated in previous works, our phylogenetic analysis indicates that the ?Notohippidae? do not constitute a monophyletic group, as Argyrohippus, Notohippus and Toxodontidae are recovered as a clade. Internal relationships within this clade are not resolved in any of the phylogenetic analysis performed here. The presence of N. toxodontoides in the faunal assemblage found at the Río Bote locality adds to its previous records in Santa Cruz (Kar-Aiken and Cerro Centinela localities) province, Argentina, and Sierra Baguales locality in Chile.