Paleobiology of avian and mammalian fossil footprints from the south of South America

KRAPOVICKAS, VERONICA; MARSICANO, CLAUDIA; MANGANO, MARIA GABRIELA

Bristol

Congreso; 69th Annual Meeting Society of Vertebrate Paleontology; 2009

Three consecutive fossil tetrapod footprint assemblages were studied from Cenozoic non-marine strata of the Vinchina Basin in northwestern Argentina (La Rioja). The footprint assemblages are preserved at the Vinchina (Oligocene to Early Miocene) and Toro Negro (Miocene to Early Pliocene) formations. The oldest assemblage (I) occurs at the base of the Upper Member of the Vinchina Formation at Quebrada de La Troya. In contrast, Assemblage II corresponds to specimens recorded by Bonaparte in the 60’s near the top of the Vinchina Formation at the nearby Quebrada del Yeso. The youngest assemblage (III) was documented in the Lower Member of the overlying Toro Negro Formation at Quebrada de La Troya. All three assemblages contain footprints representing the activity of large cursorial birds, such as Rheiformes and phororhacids, as well as those of macraucheniids. Furthermore, assemblages II and III also share footprints most-likely produced by shorebirds and by large tardigrad mammals.  By contrast, the oldest assemblage (I) records several distinct footprints not present in the other assemblages i.e. Gruipeda isp., small tridactyl rodent-like footprints and large tetradactyl rodent-like footprints. Similarly, assemblage II only records footprints attributable to Ralliformes. The youngest assemblage (III) is the most diverse, including perching birds, medium heteropod rodent-like mammals, medium-small tardigrads, and proterotheriids, besides those shared with the other two assemblages. Although, these tetrapod fossil footprint assemblages are preserved in slightly different depositional environments, they are spatially closely related. Thus, they represent, at least partially, the evolution and composition of the local fauna and therefore adding valuable information unexpressed by the scarce Cenozoic tetrapod body fossil record in the region.