FIORELLI lucas Ernesto
congresos y reuniones científicas
Tetrapod burrows from the Late Triassic Chañares Formarion, La Rioja, Argentina
LUCAS E. FIORELLI; MARTÍN HECHENLEITNER; AGUSTÍN MARTINELLI; SEBASTIÁN ROCHER; MIGUEL EZPELETA; JEREMÍAS TABORDA; MARTÍN EZCURRA; JULIA DESOJO
Jornada; XXX JORNADAS ARGENTINAS DE PALEONTOLOGIA DE VERTEBRADOS; 2016
The first report of tetrapod burrows from the early Late Triassic (early Carnian) Chañares Formation, La Rioja (Northwestern Argentina), is presented here. The burrows were found in different localities of the unit, being abundant in the first 15 meters. They occur associated with a transitional fauna dominated by dicynodontians, cynodontians, rhynchosaurids, and basal pseudosuchians at the first ~8 meters of the sequence, which is quite distinctive from that represented by the typical Chañares fauna upwards. The burrows were found within incipient paleosol profiles with volcaniclastic parent materials, anddeveloped over ephemeral channelized flows, under semi-arid climate conditions. The burrow systems are characterized by long, multiple branching tunnels that meander horizontally forming a complex network and display passive fill of a previously open burrow; they are cylindrical to sub-cylindrical in shape measuring between 10 to 20 cm in diameter and several meters of lateral extension. In general, these structures have a similar morphology and 3D organization to those described for the Ischigualasto Formation. The occurrence of burrow systems within paleosols formed in a semiarid environment and thepresence of large suchians (e.g., Luperosuchus) in the same levels lends support to the hypothesis that small tetrapods (e.g., Chiniquodon, Probainognathus) from the Chañares Formation would excavate burrows to avoid climate-stress conditions and/or predation. This new finding completes the gap in the fossil record of possible-tetrapod-burrows found in the Ischigualasto-Villa Union Basin. This link would greatly contribute to understand the evolution of the fossorial habits of small Gondwanan vertebrates during the Late Triassic.