Biostratigraphic significance of Darriwilian conodonts from Sierra de La Trampa (Central Precordillera, San Juan, Argentina)

摘要

The Eoplacognathus pseudoplanus Zone is defined by a conodont fauna composed by E. pseudoplanus (Viira) and Dzikodus tablepointensis (Stouge) among others in the Central Precordillera, Sierra de La Trampra region. We revised the biostratigraphical distribution and control biofacies of the conodonts D. tablepointensis and E. pseudoplanus in the Middle Ordovician of the Precordillera. This study confirms that these species has a similar biostratigraphical distribution to those of equivalent age in south-central China, Baltica and Midcontinent region. We also corroborate that the presence of D. tablepointensis is accurately positioned in the E. pseudoplanus Zone. In this paper we discuss for the first time the morphological affinities of D. tablepointensis and E. pseudoplanus elements from the Precordillera with those same species from southcentral China and Baltica. On the other hand, we review the genus "Polonodus" galerus Albanesi and propose it as Kallidontus? galerus (Albanesi), extending the biostratigraphical record of the genus Kallidontus from the late Tremadocian to middle Darriwilian.