On the taxonomic status of Neuryurus rudis (Gervais) (Xenarthra, Glyptodontidae) and some considerations about ontogenetic changes in Glyptodontidae

IRRAZABAL, MARÍA LUZ; CUADRELLI, FRANCISCO; STRACCIA, PABLO; ZURITA, ALFREDO EDUARDO; LUNA, CARLOS ALBERTO; BARASOAIN, DANIEL; REY, LUCIANO; GONZÁLEZ-RUIZ, LAUREANO

Congreso; 1st Palaeontological Virtual Congress; 2018

Universidad de Valencia

Diversity reached by Pleistocene glyptodonts in Southern South America was probably lower than previously believed, as recent evidence suggested. In relation to it, one of the intriguing aspects of the group has been the supposed absence of juvenile specimens in the fossiliferous record. However, the increase of knowledge about the morphologic ontogenetic variations of glyptodonts had shown that several of the recognized Pliocene and Quaternary taxa actually belong to juvenile specimens. We present evidence supporting that the type specimen (MHNN n/n) of the enigmatic Neuryurus rudis Gervais, integrating the biozone of the Ensenadan Age/Stage (early-middle Pleistocene), belongs to a juvenile specimen of Panochthus sp. The osteoderms of the carapace present an exposed surface consisting of a finely spongy tissue with small foramina and absence of defined figures, while the internal surface shows wide neurovascular foramina (~2mm) and the articular areas are poorly developed, characteristics observed in juvenile specimens of some Glyptodontidae. The caudal tube, conformed by contiguous osteoderms and similar to those of the carapace, also presents the typical design of lateral, dorsal and marginal figures of species of Panochthus Burmeister. These observations indicate that Neuryurus rudis correspond to a different ontogenetic stage of this taxon; in addition, the progressive transformation of this caudal tube into a rigid structure could represent a more derived evolutionary pattern of some Glyptodontidae. From the stratigraphic viewpoint, our field observations indicate that type material of this species (from the surroundings of Carcarañá, Santa Fe province) comes from the Tezanos Pinto Formation (late Pleistocene).