SYSTEMATIC UPDATE OF LITOPTERNA AND NOTOUNGULATA (MAMMALIA) FROM THE ?MESOPOTAMIAN? (LATE MIOCENE) OF ENTRE RÍOS PROVINCE, ARGENTINA

SCHMIDT, GABRIELA I.

Mendoza

Congreso; 4th International Palaeontological Congress; 2014

IANIGLA-CCT-CONICET-MENDOZA

The richness of fossil vertebrates from the base of the Ituzaingó Formation (Entre Ríos Province) has been known since the beginning of the XX century, and the fossiliferous levels were named ?Conglomerado osífero? or ?Mesopotamiense,? whose fossils, especially the mammals, constituted the base of the so-called ?mesopotamiense? fauna. Within it, two groups of native ungulates were revised: the Litopterna, represented by the families Proterotheriidae and Macraucheniidae, and the Notoungulata, represented by the families Toxodontidae and Interatheriidae. Many of the species identified in the ?Mesopotamiense? fauna were previously poorly characterized and sometimes based on very incomplete specimens. In this sense, the study of many unpublished specimens has enabled updating the taxonomic diversity of the formation, emending or extending the diagnoses of recognized genera and/or species, and analyzing species relationships in a phylogenetic scheme (except the Family Interatheriidae). Within Proterotheriidae (Litopterna), Brachytherium cuspidatum Ameghino, previously considered a nomen dubium, was revalidated, and a sexual dimorphism was recognized for this taxon based on specimens with metric but no morphologic differences. Also, the species Neobrachytherium ameghinoi Soria and Proterotherium cervioides Ameghino were maintained while Epitherium? eversus (Ameghino) was reclassified as Diadiaphorus eversus (Ameghino). In the case of the Family Macraucheniidae (Litopterna), Scalabrinitherium bravardi Ameghino and Oxyodontherium zeballosi Ameghino were recognized. Within each one, metric - but no morphologic - differences also led to the proposal of the existence of sexual dimorphism. Moreover Paranauchenia denticulate (Ameghino), Promacrauchenia antique (Ameghino), cf. Promacrauchenia and Cullinia sp. were recognized. Among Notoungulata, Toxodontidae is represented by Dinotoxodon paranensis (Laurillard), Stenotephanos plicidens (Ameghino), Haplodontherium wildei Ameghino and cf. Pisanodon Zetti. This implies a remarkable reduction in the diversity of toxodontids previously established for the ?Mesopotamiense?. In the particular case of Stenotephanos, this was recognized as the valid name instead of the traditionally accepted Xotodon. Other taxa such as Toxodontherium compressum Ameghino, Adinotherium? paranense Ameghino, Berroia? sp., Toxodon protoburmeisteri Ameghino, and Dilobodon lutarius Ameghino were considered as nomina dubia due to the fragmentary, poorly diagnostic material attributed to them. The Typotheria notoungulates of the Family Interatheriidae are represented by Protypotherium antiquum Ameghino and Munizia paranensis Kraglievich, each taxon represented by one specimen.