A review of confusing glyptodonts: Neuryurus rudis (Gervais) (Xenarthra: Glyptodontidae) and its implications for the ontogeny of Panochthus Burmeister

Glyptodonts (Xenarthra, Cingulata) were large and armoured herbivores forming part of the Cenozoic megafauna of the Americas. Numerous species were recognised based on differences in the ornamentation of their dorsal carapace osteoderms. Phylogenetic and morphological studies indicate that this high diversity was overestimated since many of the variations once used to define species actually reflect ontogenetic changes or taphonomic alterations. Here, we present a detailed revision of the enigmatic Neuryurus rudis (Gervais, 1878), considered a keyelement of the Ensenadan Age/Stage (Early Middle Pleistocene) in Argentina. Our analysis demonstrates that the type material of N. rudis belongs to a juvenile specimen of Panochthus Burmeister 1866. A comparative examination of caudal tubes in Panochthus reveals the ontogenetic sequence of this structure, representing the most complete developmental record described for glyptodonts to date. Most of the taxa traditionally assigned to the tribe Neuryurini (Neuryurus, Urotherium Castellanos 1926 and Pseudoeuryurus Ameghino 1889) are reinterpreted as juvenile or taphonomically altered specimens. This revision clarifies that the diversity of Late Pleistocene glyptodonts in southern South America (i.e. Argentina, Uruguay, Paraguay, and southern Brazil and Bolivia) is restricted to four species: Neosclerocalyptus paskoensis (Zurita 2002), Doedicurus clavicaudatus (Owen 1847), Glyptodon reticulatus Owen 1845, and Panochthus tuberculatus Burmeister 1866.