NEW INSIGHTS INTO THE PHACOPID TRILOBITE REEDOPS RICHTER AND RICHTER, 1925 IN THE LOWER DEVONIAN FROM ARGENTINA

Abstract

Abstract. The phacopid trilobite Reedops is a worldwide Devonian indicator not earlier than Pragian. Three poorly known specimens were reported in Argentina by Baldis and Peralta in 1991, putatively coming from the Silurian and Devonian of the San Juan Province, but neglected in subsequent contributions. After that first mention, Reedops cf. bronni was reported from the Lower Devonian of the La Rioja Province, by Holloway and Rustán in 2012. We describe herein an additional specimen from that same locality. In addition, we revised the specimens of Baldis and Peralta: Reedops sp. b from the Talacasto Formation at Cerro del Molle section, corresponds to Echidnops taphomimus; the specimen reported as Reedops sp. b from the upper Silurian to probably Devonian of the Rinconada Formation at Villicum Range, is an indeterminate genus; and the third specimen from the Talacasto Formation at the Río de las Chacritas section (Reedops sp. a) is confirmed as Reedops cf. bronni. The biozone of Reedops would be restricted to the lower (but not the lowermost) dark fine-grained part of the Talacasto Formation in the Argentine Precordillera. A Pragian age is in accordance with palynological information about the Lochkovian/Pragian boundary in the Argentine Precordillera, otherwise virtually devoid of marker macrofossils. Despite its biostratigraphic significance, Reedops is very scarce and the bearing interval exhibits no lithological variations useful for correlation. Hence, the co-occurring and more abundant (although endemic) trilobites Echidnops taphomimus and talacastops zarelae among others,  represent a significant assemblage for identification of the basal Pragian in the Argentine Precordillera.