ON THE TAXONOMIC STATUS OF NEURYURUS RUDIS (GERVAIS) (XENARTHRA, GLYPTODONTIDAE) AND SOME CONSIDERATIONS ABOUT ONTOGENETIC CHANGES IN GLYPTODONTIDAE

IRRAZABAL, LUZ; ZURITA, ALFREDO E.; REY, L.; CUADRELLI, FRANCISCO; LUNA, CARLOS; GONZÁLEZ RUIZ, LAUREANO R.; STRACCIA, P.; BARASOAIN, DANIEL

Congreso; Ist Palaeontological Virtual Congress; 2018

Diversity reached by Pleistocene glyptodonts in Southern South America was probably lower thanpreviously believed, as recent evidence suggested. In relation to it, one of the intriguing aspects ofthe group has been the supposed absence of juvenile specimens in the fossiliferous record.However, the increase of knowledge about the morphologic ontogenetic variations of glyptodontshad shown that several of the recognized Pliocene and Quaternary taxa actually belong to juvenilespecimens. We present evidence supporting that the type specimen (MHNN n/n) of the enigmaticNeuryurus rudis Gervais, integrating the biozone of the Ensenadan Age/Stage (early-middlePleistocene), belongs to a juvenile specimen of Panochthus sp. The osteoderms of the carapacepresent 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 thearticular areas are poorly developed, characteristics observed in juvenile specimens of someGlyptodontidae. The caudal tube, conformed by contiguous osteoderms and similar to those of thecarapace, also presents the typical design of lateral, dorsal and marginal figures of species ofPanochthus Burmeister. These observations indicate that Neuryurus rudis correspond to a differentontogenetic stage of this taxon; in addition, the progressive transformation of this caudal tube intoa 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).