DESOJO Julia Brenda
congresos y reuniones científicas
New tetrapod specimens and chronostratigraphy of the Late Triassic Ischigualasto Formation at Cerro Las Lajas (La Rioja Province), northwestern Argentina.
LANGER, M.C.; DESOJO, J. B.; DA ROSA; EZPELETA, M.; EZCURRA, M.D.; MARTINELLI, A. G.; VON BACZKO, M. B.; FIORELLI, L.E.; MONTEFELTRO, F.; RAMEZANI, J.
Congreso; 5th International Paleontological Congress; 2018
The early diversification of most modern tetrapod clades, such as lissamphibians, lepidosauromorphs, testudinatans, archosauromorphs, and mammaliaforms, started during the Early−Middle Triassic, and by the Late Triassic most of them were abundant and diverse. The Ischigualasto Formation of northwestern Argentina (late Carnian−early Norian), mainly explored at the Hoyada de Ischigualasto (San Juan Province), is one of the continental units that has best documented this transition. Recent fieldwork on the Ischigualsto Formation at Hoyada del Cerro Las Lajas (La Rioja Province) allowed us to considerably improve the knowledge of the vertebrate record of this unit. Only three archosaur taxa based on three specimens were previously reported from Cerro Las Lajas by Bonaparte in the 70?s: the holotypes of the ornithosuchid Venaticosuchus rusconii and the ornithischian Pisanosaurus mertii, as well as a specimen recently referred to the crocodylomorph Trialestes romeri. Here, we report additional fossil remains from the lower third (70m to 200m) of the Ischigualasto Formation at Cerro Las Lajas that includes: skeletons of four different species of hyperodapedontine rhynchosaurs (two of which are new), few partial skeletons of the traversodontid Exaeretodon sp., plus incomplete skeletons of an aetosaur, a proterochampsid archosauriform (Proterochampsa sp.), a non-shuvosaurid poposauroid, and a probainognathian cynodont (cf. Ecteninion). These taxa, except for three of the rhynchosaur species and probably the poposauroid, were previously reported from the two lowermost members of the Ischigualasto Formation at Hoyada de Ischigualasto. Our new high-precision U-Pb geochronology by the CA-ID-TIMS method suggests that the Cerro Las Lajas captures a near-complete succession of the Ischigualasto Formation and that the faunal assemblage presented here allows an assignment to the Scaphonyx-Exaeretodon-Herrerasaurus biozone of the Ischigualasto Formation at Hoyada de Ischigualasto. However, no diagnostic fossil remain has yet been discovered from the upper two-thirds of the unit at Cerro Las Lajas to be able to compare to the faunal assemblage of the Ischigualasto Formation in San Juan.