Bone microstructure of Proterochampsia from the Chañares Formation

PREVITERA ELENA; ARCUCCI ANDREA BEATRIZ; MANCUSO ADRIANA CECILIA

Puerto Madryn

Otro; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2018

Asociación Paleontólogica Argentina

Proterochampsids are South American endemic non-archosaurian archosauriforms have a restricted temporal distribution, and which origin,diversification and disappearance happened in a very short period of time in the Late Triassic. Some contributions about the anatomical andphylogenetic knowledge of proterochampsids have been published, but paleobiological hypothesis about the group are still scarse. We developeddetailed histological descriptions and evaluated paleobiological hypotheses about the Chañares proterochampsids. For this purpose, seven thin sections of long bones belonging to six proterochampsian specimens were analyzed. These show proterochampsian diagnostic characters, but they did not display autopomorphies that allow us different among the Chañares taxa. The histological examination revealed a predominance offibrolamellar tissue suggesting a rapid periosteal osteogenesis, and therefore an overall fast bone growth. The absence of large amounts of mature secondary osteons is comparable with that recently observed in aquatic non phylogenetically related placodonts. The existence of discontinuities (LAGs) expressed the capability to rapid response to environmental changes. The proterochampsid samples display higher growth rates than those reported in pseudosuchians and other basal archosauromorphs, resembling some dinosauromorphs, as well as some basal dinosaurs.