Exceptional Skull of Huayqueriana (Mammalia, Litopterna, Macraucheniidae) From the Late Miocene of Argentina: Anatomy, Systematics, and Paleobiological Implications

Analía M Forasiepi,Eli Amson,Ross D E Macphee,Santiago Hernández Del Pino,Gabriela I Schmidt,Camille Grohé

doi:10.1206/0003-0090-404.1.1

Abstract

ABSTRACT The Huayquerias Formation (Late Miocene, Huayquerian SALMA) is broadly exposed in west-central Argentina (Mendoza). The target of several major paleontological expeditions in the first half of the 20th century, the Mendozan Huayquerias (“badlands”) have recently yielded a significant number of new fossil finds. In this contribution we describe a complete skull (IANIGLA-PV 29) and place it systematically as Huayqueriana cf. H. cristata (Rovereto, 1914) (Litopterna, Macraucheniidae). The specimen shares some nonexclusive features with H. cristata (similar size, rostral border of the orbit almost level with distal border of M3, convergence of maxillary bones at the level of the P3/P4 embrasure, flat snout, very protruding orbits, round outline of premaxillary area in palatal view, and small diastemata between I3/C and C/P1). Other differences (e.g., lack of sagittal crest) may or may not represent intraspecific variation. In addition to other features described here, endocast reconstruction utilizin...

Highlights

By any measure, the morphological diversification of South American native ungulates (SANUs) during the Cenozoic was extraordinary
Phylogenetic analysis failed to resolve the position of IANIGLA-Vertebrate Paleontology (PV) 29 satisfactorily, a result possibly influenced by intraspecific variation
The various families of South American native ungulates grouped as Litopterna thrived on that continent from at least the late Paleogene to the beginning of the Holocene

Summary

Introduction

The morphological diversification of South American native ungulates (SANUs) during the Cenozoic was extraordinary. In terms of taxonomic diversity, Notoungulata was the most successful of the SANU orders, followed by Litopterna with about a hundred species discriminated at present (Cifelli, 1983, 1993; Cifelli and Soria, 1983; Bond, 1986, 1999; Bond et al, 1995, 2001; Cifelli and Guerrero, 1997; Soria, 1981, 2001; Scherer et al, 2009; Schmidt and Ferrero, 2014) Despite their numerous morphological specializations, according to collagen proteomic studies these two SANUs appear to have shared a common ancestry and are most closely related to Perissodactyla among major extant placental taxa (Welker et al, 2015; Buckley, 2015).

Methods

Findings

Discussion

Conclusion