Arachnostega gastrochaenae Bertling (traza fósil) en las secuencias volcaniclásticas de la Formación Suri, Sistema de Famatina, Argentina

The occurrence of Arachnostega gastrochaenae Bertling on internal moulds of Lower Paleozoic mollusks, brachiopods and trilobites is reported. The material was found in volcaniclastic sediments of the Arenig Suri Formation, cropping out in the Sierra de Narváez, Catamarca Province (northwestern Argentina). The ichnospecies displays a burrow network characterized by a branching pattern with variable diameter and slightly irregular internal walls. The ichnogenus was originally described from Jurassic reefs and modern sediments of northern Germany. In South America, Arachnostega had only been mentioned in Argentina and Uruguay, recorded from Jurassic and probably Carboniferous-Permian strata respectively. With this new locality, we present the oldest record of Arachnostega (Lower Ordovician). Paleoecologic interpretations are done by means of the particular sedimentologic setting of the Suri Formation. Additional occurrences of the ichnogenus in bivalve and trilobite moulds from Ordovician sequences in Europe (Spain, France and the Czech Republic), and Devonian strata of La Paz (Bolivia) are also mentioned.