The first palynologic association from the early Late Triassic Chañares Formation and the paleodiet of the megaherbivore dicynodonts

VALERIA PÉREZ LOINAZE; EZEQUIEL VERA; LUCAS E. FIORELLI; JULIA DESOJO

Río Negro

Congreso; XI Congreso de la Asociación Paleontológica Argentina; 2016

Universidad Nacional de Río Negro

The Chañares Formation supports one of the most fossiliferous early Late Triassic continental tetrapod bearing assemblages worldwide and is essential to understand the origin and early evolutionary radiation of suchians, dinosauromorphs, and mammaliaforms. However, the paleoflora of this important Triassic unit is unknown. Recently, were described the oldest megaherbivores communal latrines from the Chañares Formation composed of thousands of in situ herbivore coprolites attributed to large kannemeyeriiform dicynodonts. In this contribution, we present the coprofabric microfossil content and the first palynological assemblage recorded from the Chañares Formation. Identified remains consist mainly of fragmentary plant debris (wood, cuticles), whereas palynomorphs are notably less abundant. Among the latter, the bisacate pollen grains Alisporites Daugherty emend. Jansonius, 1971 and Platysaccus Naumova ex Potonié and Klaus, 1954 (with affinities with Corystospermales) dominate the palynological assemblage, whereas striate pollen grains and fern spores are less abundant. Most elements of the assemblage are characteristic of the Ipswich phytoprovince. It is noteworthy, however, the record of Ovallipollis Krutzsch emend. Schuurman, 1976 and Ellipsovelatisporites Klaus, 1960, absent in this phytoprovince, but recently reported in the basin for palynofloras from the younger Ischigualasto Formation, referred to the Onslow phytoprovince. Moreover, this coprolite-paleofloristic association would possibly be related with the paleodiet and feeding behavior of Chañares dicynodonts. The Chañares coprolites represent a window to expand our knowledge of the ecosystems of the early Late Triassic of Gondwana.