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Accueil du site → Doctorat → Argentine → Trazas fósiles de coleópteros coprófagos del cenozoico de la Patagonia Central. Significado evolutivo y paleoambiental

Universidad de Buenos Aires (2009)

Trazas fósiles de coleópteros coprófagos del cenozoico de la Patagonia Central. Significado evolutivo y paleoambiental

Sánchez, María Victoria

Titre : Trazas fósiles de coleópteros coprófagos del cenozoico de la Patagonia Central. Significado evolutivo y paleoambiental

Fossil brood balls of dung beetles from the cenozoic of Central Patagonia. Paleoenvironmental and evolutionary significance

Auteur : Sánchez, María Victoria

Université de soutenance : Universidad de Buenos Aires

Grade : Doctor de la Universidad de Buenos Aires en el área de Ciencias Biológicas 2009

Résumé
Scarabaeinae brood balls preserved in the geological record as traces belong to the Coprinisphaera ichnogenus, which included five icnospecies : C. ecuadoriensis, C. murguiai, C. kheprii, C. tonnii y C. kraglievichi. The ichnotaxonomic revision resulted in : a) the description of a new ichnospecies (C. isp. B), b) C. ecuadoriensis Sauer 1955 is a junior synomym of C. murguiai Roselli 1939, and c) C. murguiai autorum has a new and provisory name, C. isp. A. Thirteen Scarabaeinae species, belonging to 4 of the 5 tribes inhabiting Argentina, were studied in order to attribute these ichnospecies to possible extant producers. Micro- and macromorphology of the brood balls allowed to attribute C. kheprii and C. tonnii to Phanaeini, and C. isp. B to Canthonini. These records, which predate 30-40 millon of years the oldest body fossils of these tribes, contribute significatively to its evolutionary history in South America. A high-resolution ichnostratigraphic study was performed based on 1200 specimens collected from 14 stratigraphic levels (paleosols) in the Sarmiento Formation (Middle Eocene-Lower Miocene) at Gran Barranca locality (Chubut, Argentina). Density per square meter, relative abundance of ichnospecies, equatorial diameter, and wall thickness were measured. These data allowed to estimate the number of producers and to dintinguish 6 episodes in the evolution of dung beetles and of the related grasslands of Patagonia. Two trace fossils, excavated in Coprinisphaera (Tombownichnus pepei and Lazaichnus fistulosus), were described. They indicated the presence of cleptoparasites and detritivores from the dung community. The analysis of the differences in the total number of phytoliths and morphotype frequencies among Coprinisphaera wall, filling, and paleosol, showed that the original soil wall was added with dung fibers. This evidence revealed aspects of dung beetle behavior and mammal diets.

Mots clés : SCARABAEINAE ; BOLAS DE CRIA ; ICNOGENERO COPRINISPHAERA ; REGISTRO FOSIL ; CENOZOICO ; PATAGONIA CENTRAL ; FITOLITOS ; TRAZAS ASOCIADAS ; SCARABAEINAE ; BROOD BALLS ; ICNOGENUS COPRINISPHAERA ; FOSSIL RECORD ; CENOZOIC ; CENTRAL PATAGONIA ; PHYTOLITHS ; ASSOCIATED TRACES

Présentation (Biblioteca Digital)

Version intégrale

Page publiée le 8 mars 2016, mise à jour le 3 juillet 2017