Trilobites from the Suri Formation (Lower Ordovician; Floian), Famatina Belt, Argentina

Abstract

A new trilobite fauna from the lower part of the Suri Formation (upper Floian) exposed in the central Famatina Belt, west Argentina, is reported. Three new species are described: Dividuagnostus tortelloi sp. nov., Bienvillia chaya sp. nov. and Hypermecaspis edselbrussai sp. nov. The remaining taxa include Nambeetella sp., Changchowilla sp., Porterfieldia sp. and undetermined telephinids. The trilobite assemblage is largely dominated by Hypermecaspis, andcomposed of a combination of sighted (olenids), blind (raphiophorids, shumardiids) and giant eyed (telephinid) trilobites. The association matches the olenid biofacies recognised elsewhere in the Early Ordovician. This is the first well documented olenid biofacies recorded in Floian successions of western Argentina. The assemblage thrived in a largely volcanic setting, associatedwith environmental restriction linked to the early stages of evolution of the volcanic-arc.