BIOSTRATIGRAPHIC IMPLICATIONS OF THE PHACOPID REEDOPS AND OTHER CO-OCURRING TRILOBITES IN THE PRAGIAN (LOWER DEVONIAN) OF THE ARGENTINE PRECORDILLERA

RUSTÁN, J.J.; PERALTA, S H

Buenos Aires

Congreso; XII Congreso de la Asociación Paleontológica Argentina; 2021

Asociación Argentina Paleontología

The phacopid trilobite Reedops is considered a Pragian indicator based on records from Europe, North America and northern Africa. Three poorly known specimens were reported from Argentina by Baldis and Peralta in 1991, putatively coming from the Silurian and Devonian of the San Juan Province. However, due to the lack of illustrations and repository numbers, these fossils were neglected in subsequent contributions. After that first mention, Reedops cf. bronni was certainly recorded in Argentina from isolated outcrops of the lower stratigraphic interval of the Lower Devonian Talacasto Formation at Sierra de las Minitas in the La Rioja Province, to the north by Holloway and Rustán. We recently revised the original specimens of Baldis and Peralta haused at the Universidad Nacional de San Juan. The eroded specimen reported as Reedops sp. b from the Talacasto Formation at Cerro del Molle section, most probably correspond to Echidnops taphomimus, on the basis of a very well-expressed vincular furrow medially, wide and strongly tuberculated glabella and a ridge-like posterior border. In turn, the specimen reported as Reedops sp. b from the Upper Silurian of the Rinconada Formation at the La Pola Creek section, corresponds to a different indeterminate phacopid genus, based on the well-expressed vincular furrow, wide tubercled glabella and thoracic axial rings with large tubercles or a transverse ridges. The specimen reported as Reedops sp a, from the Talacasto Formation at the Río de las Chacritas section, indeed belong to this genus based on the medially effaced vincular furrow, forwardly outstanding glabella and antero-laterally located eyes.