CONICET | Buscador de Institutos y Recursos Humanos

Talampaya and Tarjados formations correspond to the initial stages of Ischigualasto-Villa Unión Basin filling, and record the oldest post-Permian events in the region. The sequence consists of red beds deposited essentially by ephemeral alluvial and fluvial systems, and overlay in discordance a Permian unit (Patquía =La Colina Formation). Until present contribution, only a manus-pes pair track of a putative therapsid was reported from the Talampaya Formation, whereas, fragmentary skeletal remains of dicynodonts was the only mention of tetrapods from the Tarjados Formation. Here, we disclose new material found, in recent field work at the upper member of the Tarjados Formation from the equivalent levels where dicynodont remains were previously found. New material includes likely footprints from tetrapod in transversal section associated in the same levels with large burrows of morphology and dimensions comparable with burrows in which small therapsid remains were found. In addition, an isolated vertebra of a medium-sized archosaur (approx. 3cm long and 4 cm high) was collected. The new findings enhance our knowledge of the post-Permian tetrapod fauna from Argentina. Thus, during the initial stage of basin filling, as part of the beginning of the post-Permian recovery, two groups of tetrapods, archosaurs and therapsids, were already present. Basal archosaurs and therapsids are also known from the Early Triassic of South Africa and the Middle Triassic of Brazil, although the fossil record is comparatively scarce in theTalampaya-Tarjados faunal association.