INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Direct and indirect evidence of microorganism interactions with tetrapod remains from the Triassic of Argentina.
BENAVENTE, CECILIA; ARCUCCI ANDREA ; PREVITERA ELENA; MANCUSO ADRIANA; IRMIS RANDALL
Congreso; 11º Congreso de la Asociación Paleontológica Argentina; 2016
Asociación Paleontológica Argentina
The Upper Triassic Chañares Formation preserves a fluvial environment with significant floodplain development where the abundant and diverse Chañares Fauna lived. Recent radioisotopic ages constrain the Chañares Formation to the early Carnian, therefore, the time between the PT boundary, recorded in the Talampaya Formation, and the first rich Triassic fauna in the Ischigualasto-Villa Unión Basin is expanded. The Chañares Formation includes a rich tetrapod fossil record with extraordinarily good bone preservation, both inside and outside carbonate concretions. Recent studies reveal chemical and direct evidence ofmicroorganisms associated with tetrapod skeletal elements. Specific kind of corrosion was observed on the surface of bones from a skeleton found in the floodplain sediments. This corrosion is interpreted as the result of indirect action of aerobic decay organisms that created a microenvironment in subaerial deposition and chemistry that exacerbated the corrosion during pre-burial processes. In addition, we have observed the presence of clotted micrite in the surrounding sediment of the carcass. This evidence suggests that the development of heterotrophic anaerobic/aerobic bacteria affected the chemical composition of the matrix immediately in contact with the bone, triggering alkalinity and ultimately leading to calcite precipitation. These indirect evidences are further supported by the presence of coccoid structures, observed by electronic microscope images in tetrapod coprolites. These structuresmay represent fossils of microbial origin, most probably coccoid Gram-negative bacteria, which in dense populations inhabit the digestive tract of living vertebrates.