DESOJO Julia Brenda
A new stahleckeriid dicynodont record from the late Ladinian-?early Carnian levels of the Chañares Formation (Ischigualasto-Villa Unión Basin) of northwestern Argentina
ESCOBAR, JUAN A.; MARTINELLI, AGUSTÍN G.; EZCURRA, MARTÍN D.; LUCAS E. FIORELLI; DESOJO, JULIA B.
JOURNAL OF SOUTH AMERICAN EARTH SCIENCES
PERGAMON-ELSEVIER SCIENCE LTD
The kannemeyeriiforms of the latest Ladinian-?early Carnian Chañares Formation (Ischigualasto-Villa UniónBasin) exemplify the historical taxonomic controversies of several South American dicynodonts. Three taxawere originally recognized based on skull anatomy: ?Chanaria? platyceps and two species of Dinodontosaurus(genus otherwise known in the Pinheiros-Chiniquá Sequence, Brazil), but in a recent taxonomic revisionthey were all synonymized in a single valid species (i.e., Dinodontosaurus brevirostris). The only postcranialrecord includes some undescribed specimens referred to D. brevirostris, an indeterminate shoulder girdle(MCZ 3459), and an ulna recently referred to Stahleckeria sp. Here we describe a new, large dicynodontspecimen (CRILAR-Pv 82) from the Tarjadia Assemblage Zone (AZ) of the lowermost levels of the ChañaresFormation, consisting of a right scapula, left ilium, sternum, and a few indeterminate fragments. The tall,dorsally expanded scapular blade with anteroventrally inclined dorsal margin and the anterolaterally directedacromion process broadly match the stahleckeriid morphotype. CRILAR-Pv 82 shares with Stahleckeriapotens a sharp, vertical scapular spine on the anteroventral margin of the scapular blade, markedly convexin anterior view. The ?hook-shaped? curvature of the preacetabular iliac process also resemblesStahleckeria potens and Eubrachiosaurus browni. These features differ at least with the Brazilian specimens ofDinodontosaurus (D. tener). The available data shows that MCZ 3459 also fits the stahleckeriid morphology,becoming the first historical record of the clade for the unit. A rigorous comparison with D. brevirostris willawait the examination of more complete specimens. The dicynodont postcrania described so far from theChañares Formation represent the oldest record of Stahleckeriinae in the Ischigualasto-Villa Unión Basin,expanding back its Argentinian record very likely beyond the Ladinian-Carnian boundary.