Early Jurassic brachiopods from Chubut Province (Argentina): a preliminary report

M.O. MANCEÑIDO Y S.M. FERRARI

Simposio; V Simposio Argentino Jurásico; 2013

The purpose of this preliminary account is to present a review summarizing the current state of knowledge about the brachiopod fauna from Early Jurassic marine deposits of Chubut Province. Data supplied in pioneering contributions from traditional authors, such as Feruglio or Wahnish de Carral Tolosa, who produced earliest descriptions and illustrations of Liassic brachiopods from such provenance, are updated and supplemented by new findings, several of them still unpublished, due to contemporary geologists and palaeontologists. From a modern lithostratigraphic viewpoint, Lower Jurassic marine sedimentary units that have yielded fossil brachiopod assemblages include, for instance, the Osta Arena and Mulanguiñeu Formations, which were accumulated within the CentralPatagonian Basin and crop out in the central and south western extra-Andean region of Chubut Province, respectively. Regarding the systematic spectrum recognized thus far, the phylum is represented by four rhynchonelliform orders: namely, the Rhynchonellida, Terebratulida (both short- and long-looped), Spiriferinida and Thecideida (listed in decreasing order of relative abundance). On the other hand, certain previous records of inarticulate brachiopods occurring in allegedly Lower Jurassic deposits have been disregarded, because they correspond in fact to Permian ones, instead. Finally, the biostratigraphical significance and palaeobiogeographical implications of the Pliensbachian-Toarcian brachiopod assemblages reported herein are also outlined.