FIRST FISH REMAINS FROM THE EARLIEST LATE TRIASSIC OF THE CHAÑARES FORMATION (LA RIOJA, ARGENTINA) AND THEIR PALEOBIOGEOGRAPHIC IMPLICATIONS

GOUIRIC CAVALLI, S.; DESOJO, JULIA; EZCURRA, M; FIORELLI, L.; MARTINELLI, A.

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2016

0002-7014

We describe fish material collected from the lowermost Upper Triassic continental levels of the Chañares Formation (Campo de Córdoba and El Torcido localities): a fragmentary dermal skull roof bone that is assigned to Mawsoniidae based on its ornamentation consisting of coarse ridges and wide shallow grooves; and patches of ganoid scales that are referred to cf. Pseudobeaconiidae based on the presence of an elevated central region in most of the scales. However, unlike pseudobeaconiids, these scales have an ornamentation pattern consisting of concentric and/or parallel ganoine ridges covering their surface. These scale patches are the first vertebrate fossil remains collected in the upper member of the Chañares Formation and we provide a brief taphonomic approach for it. The Mawsoniidae described here is the southernmost record of the family, being the first coelacanth from Argentina and the first Triassic mawsoniid from South America. Freshwater mawsoniid coelacanths were stablished in Laurasia during the Late Triassic; the new Gondwanan record may denote that similar weather conditions (hot and arid but with seasonal precipitations) were present in north and south Pangea during this period