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

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

JOURNAL OF VERTEBRATE PALEONTOLOGY

SOC VERTEBRATE PALEONTOLOGY

Lugar: Lawrence; Año: 2018

0272-4634

The specimens herein presented comefrom the Río Bote locality, Santa Cruz Formation (early Miocene), Santa CruzProvince, Argentina. They include the most complete cranial material of the ?Notohippidae?Notohippus toxodontoides, and otherremains that allow increasing the knowledge on mandible and dentition. The new remains permit the extensionof the original description proposed by Ameghino in the XIX century, andprovide some data on the ontogenetic variation in the dental traits of thisspecies. Notohippus differs from the Deseadan?Colhuehuapiangenus Argyrohippus in the following features:discontinuous dentition; C and p1 absent; shorter P2?M3/p2?m3 series; crown of I1 highly curved; uppermolars with less developed parastyle and paracone fold, less undulate ectoloph,deeper distolingual groove of M3 directed more lingually, and presence of a veryshallow distolabial groove; incisiviform lower canine; and lower molars with posterolabial angle of thetalonid more rounded, and narrower trigonid valley. As stated in previousworks, our phylogenetic analysis indicates that the ?Notohippidae? do notconstitute a monophyletic group, as Argyrohippus,Notohippus and Toxodontidae arerecovered as a clade. Relationships among these taxa are not resolved in the phylogeneticanalysis under equal weights, but a different variant, using extended impliedweights, places Argyrohippus (with anextremely low support) as the sister taxon of the toxodontids, being Notohippus the sister taxon of both ofthem. The presence of N. toxodontoidesin the faunal assemblage found at the Río Bote locality adds to its previousrecords in Santa Cruz (Kar-Aiken and Cerro Centinela localities) provinces, Argentina,and Sierra Baguales locality in Chile.