CONICET | Buscador de Institutos y Recursos Humanos

Abstract. The plectambonitoid brachiopod Gatosella muricata n. gen. n. sp. is described from the uppermost nodular limestones of the San Juan Formation. The well constrained early Darriwilian age of these beds leaves Gotosella as one of the oldest known plectambonitoideans possessing an undercut cardinal process. A phylogenetic analysis of representative genera bearing this character reveals that the new Precordilleran genus is a basal member of the subfamily Aegiromeninae (as presently defined). Parsimony analysis supports the existence of three subclades which may be considered as having familial rank in the Linnean classification: Aegiromenidae, Hesperomenidae and Sowerbyellidae, and also indicates that the xenambonitins are more closely related to the sowerbyellids than to any other group.