Regarding the real diversity of Glyptodontidae (Mammalia, Xenarthra) in the late Pliocene (Chapadmalalan Age/Stage) of Argentina

Abstract

A large diversity of Glyptodontidae has been proposed as characterizing the Chapadmalalan Age (Pliocene). Most of these taxa were recognized on the basis of partial dorsal carapaces and/or caudal tubes, whereas the main diagnostic characteristic is a particular morphology of the exposed surface of the osteoderms. From a biostratigraphic point of view some species are biostratigraphically important. The Upper Chapadmalalan is based on the Paraglyptodon chapadmalensis biozone. Both the re-evaluation of the type and referred materials and new significant findings from the Chapadmalal and El Polvorín Formations indicate that the diversity of Pliocene Glyptodontidae is more limited than previously supposed. The particular morphology of the exposed surface of the osteoderms that characterizes some of the species actually corresponds to a taphonomic alteration, which results in a non-real ornamentation pattern. Thus, the Glyptodontinae P. chapadmalensis must be replaced as a fossil guide because neither this species nor the species included in the genera Urotherium, Trachycalyptus and Lomaphorus are well characterized. Taking into account the diversity of Glyptodontidae for this lapse, the Glyptodontinae are very scarce (a situation that contrasts with its records in the Pleistocene), whereas Eosclerocalyptus, "Plohophorini" (Plohophorus) and Doedicurinae (cf. Eleutherocercus antiquus) are among the most recorded taxa.

A new species of Eutatus Gervais (Xenarthra, Dasypodidae) from the Late Pleistocene of the Northern Pampean Region, Argentina

“…However, the variations that exist within osteoderms from the dorsal carapace of a single individual, in Dasypodidae and Glytodontidae, has been subject of a large number of non-valid species generating the consequent overestimation of the diversity of these groups (Krmpotic et al, 2009a;Zurita et al, 2016, Cruz et al, 2016. To reduce the variation existing in the osteoderms due to location within the carapace, we have focused on a specific type of osteoderms from homologous regions between specimens.…”

“…This has also led to the creation of nonvalid species based on juvenile or sub-adult specimens. This subject was recently reviewed by several authors (Zurita et al, 2011(Zurita et al, , 2016Cruz et al, 2016) and the shape of osteoderms from a juvenile specimen of Glyptodon sp. were described .…”

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“…Among them, Eutatini armadillos (Euphractinae) are characterized by presenting a very rudimentary pseudo-scapular shield (Krmpotic et al, 2009), and some extinct euphractine armadillos such as those belonging to the genus Prozaedyus Ameghino (1891) even developed a dorsal carapace that was composed just by mobile bands and a pelvic shield (Barasoain et al, 2020). In turn, glyptodonts (Glyptodontidae) developed an undivided and rigid dorsal carapace composed by fixed osteoderms only (Zurita et al, 2016).…”

Phylogenetic affinities and morphology of the Pliocene cathartiform Dryornis pampeanus Moreno & Mercerat

“…24; Zurita et al . 89; Beck & Taglioretti 6). Moreover, recent studies indicate that most taxa are present in both the Chapadmalal and Monte Hermoso Formations (Tomassini et al .…”