A new stahleckeriid dicynodont record from the late Ladinian-?early Carnian levels of the Chañares Formation (Ischigualasto-Villa Unión Basin) of northwestern Argentina. (August 2021)

• Record Type: Journal Article
• Authors: Escobar, Juan A.; Martinelli, Agustín G.; Ezcurra, Martín D.; Fiorelli, Lucas E.; Desojo, Julia B.
• Is Part Of: Journal of South American earth sciences. Volume 109(2021)
• Publication Date: 2021-08
• Subjects: Dicynodontia -- Kannemeyeriiformes -- Stahleckeriidae -- Triassic -- Postcranium -- South America; Geology -- Latin America -- Periodicals; Earth sciences -- Latin America -- Periodicals; Geology -- Antarctica -- Periodicals; Earth sciences -- Antarctica -- Periodicals; Geology -- Caribbean Area -- Periodicals; Earth sciences -- Caribbean Area -- Periodicals; Géologie -- Amérique latine -- Périodiques; Sciences de la terre -- Amérique latine -- Périodiques; Géologie -- Antarctique -- Périodiques; Sciences de la terre -- Antarctique -- Périodiques; Géologie -- Caraïbes (Région) -- Périodiques; Sciences de la terre -- Caraïbes (Région) -- Périodiques; Earth sciences; Geology; Antarctica; Caribbean Area; Latin America; Periodicals; 550.5
• DOI: 10.1016/j.jsames.2021.103275
• Languages: English
• ISSNs: 0895-9811

Abstract

Abstract: The kannemeyeriiforms of the latest Ladinian-?early Carnian Chañares Formation (Ischigualasto-Villa Unión Basin) exemplify the historical taxonomic controversies of several South American dicynodonts. Three taxa were 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 revision they were all synonymized in a single valid species (i.e., Dinodontosaurus brevirostris ). The only postcranial record 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 dicynodont specimen (CRILAR-Pv 82) from the Tarjadia Assemblage Zone (AZ) of the lowermost levels of the Chañares Formation, 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 directed acromion process broadly match the stahleckeriid morphotype. CRILAR-Pv 82 shares with Stahleckeria potens a sharp, vertical scapular spine on the anteroventral margin of the scapular blade, markedly convex in anterior view. The "hook-shaped" curvature of the preacetabular iliac process also resembles Stahleckeria potens and Eubrachiosaurus browni . These features differ at least with the Brazilian specimens of Dinodontosaurus ( 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 will await the examination of more complete specimens. The dicynodont postcrania described so far from the Chañares 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. Highlights: New postcranial material of a dicynodont from the Chañares Formation (Triassic). The new material and an historical specimen are both referred to Stahleckeriidae. Stahleckeriids from Argentina probably date back beyond the Ladinian-Carnian boundary.