NEW CYNODONT SPECIMENS FROM LOS COLORADOS FORMATION

LEANDRO GAETANO; PABLO ALONSO MURUAGA; VERÓNICA KRAPOVICKAS; JUAN LEARDI; ALEJANDRO OTERO; CECILIA APALDETTI

Puerto Madryn

Congreso; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2018

Renovated exploration efforts since 2014 led to new findings in the Late Triassic Los Colorados Formation at the Parque Nacional Talampaya (LaRioja, Argentina). Herein we present four cynodont specimens found in the uppermost third of the unit, represented by skulls with articulated lowerjaws. The fossils are concentrated in a massive- to parallel-laminated sandy mudstone interval locally interbedded with parallel- to rippled- laminatedsandstone, representing deposition in a floodplain setting sporadically affected by sandy splays from the fluvial channels. They are incomplete and,although fractured, the bone seems mostly undeformed. The new specimens (housed at the UNLR) range from ~30% smaller to slightly larger thanthe size to those previously reported Chaliminia musteloides Bonaparte individuals, the only named cynodont from Los Colorados Fm. One of thenew specimens shows large upper canines, small upper I1 and I2 and lower i1, lower postcanines with a main central cusp flanked a mesial and adistal accessory cusp, and a coronoid process forming a low angle with the horizontal ramus of the dentary. Other specimen is notable by its lowskull, delicate, long and low coronoid process, and the absence of a marked step angle at the ventroposterior region of the dentary. A third specimenhas very large upper and lower first incisors with the I1 directed anteriorly, a relatively low horizontal ramus of the dentary, and the absence of adiastema between right and left upper incisors. Our preliminary analysis suggests that these three specimens may represent previously unregisteredforms.