Glyptodon munizi Ameghino, 1881

Glyptodon munizi Ameghino, 1881

Referred material: Almost complete skeleton: PIMUZ A/ V 461 ( Fig. 1 View Fig ); cranium and a large lateral border of the dorsal carapace: PIMUZ A/ V 462 & 472 ( Fig. 4 View Fig ); incomplete skeleton including mandible, five caudal vertebrae, distal caudal armor with associated vertebrae, one forelimb, isolated and associated foot bones, and caudal rings: PIMUZ A/ V 463 ( Figs. 5 View Fig , 8 View Fig , 9 View Fig ); sacral vertebra fragments, undetermined postcranial bones (pelvis?), 19 plates of osteoderms from the carapace, and 55 isolated or fragmented osteoderms: PIMUZ A/ V 464 ( Fig. 3 View Fig ); humerus, radius, right ulna and hand, left femur, right femur, tibia, and fibula, and plates of osteoderms from the carapace: PIMUZ A/ V 465 ( Figs. 5 View Fig , 6 View Fig ); almost complete pelvic girdle: PIMUZ A/ V 466 ( Fig. 6 View Fig ); plates of osteoderms from the carapace: PIMUZ A/ V 468; sacral vertebra fragment, caudal vertebra fragment, three fragments of the pelvic girdle, one plate of osteoderms from the carapace, and 21 isolated osteoderms: PIMUZ A/ V 469; large plate of osteoderms from the carapace: PIMUZ A/ V 470; three plates of osteoderms from the carapace, one isolated osteoderm, left hand, one foot: PIMUZ A/ V 471 ( Fig. 7 View Fig ); three plates of osteoderms from the carapace and two isolated osteoderms: PIMUZ A/ V 4142; right mandible: PIMUZ A/ V 4150.

Comment: Recent studies on the Glyptodontinae recognized only two genera for the Pleistocene, Glyptotherium Osborn, 1903 , and Glyptodon . Te first is not present in Argentina and occurs in South America in northern Venezuela and the eastern tip of Brazil (Zurita et al., 2018). I therefore focused on the genus Glyptodon , which was rich taxonomically in the past but taxonomic revisions have resulted in currently only three species being recognized (Cuadrelli et al., 2019, 2020). Only two species are known from the Pleistocene of the Pampean region: G. munizi , recorded only in the Ensenadan, and G. reticulatus Owen, 1845 , recorded only in the Lujanian (Cuadrelli et al., 2019). Our taxonomic revision was therefore focused on the reassignment to one of these two species, considering also diagnostic features of the anatomy. PIMUZ A/V 461 and PIMUZ A/V 462 and 472 crania are assigned to Glyptodon . Te former is complete and exhibits diagnostic features assignable to G. munizi such as a relatively circular orbital notch and a relatively shorter dorsoventral length of the zygomatic arches (Cuadrelli et al., 2019, 2020). However, PIMUZ A/V 461 shows descending processes of the zygomatic arches with a strong lateromedial extension accompanied by a slight medial curvature, characteristic of G. reticulatus (Cuadrelli et al., 2019) . Both specimens show a postorbital constriction and a relatively strong fronto-parietal region index, morphologies that are more strongly marked in G. munizi (Cuadrelli et al., 2019, 2020). An assignment to G. munizi is also supported by a weak trilobation of Mf1, especially on the lingual margin, in both specimens (Cuadrelli et al., 2019, 2020). Te attribution of PIMUZ A/V 461 to G. munizi is confirmed by the strong convexity of the dorsal carapace, while the part of the dorsal carapace preserved in PIMUZ A/V 462 and 472 corresponds to the caudal notch and shows a posterior elevation ending with strongly pronounced conical tubercles as in G. munizi (Cuadrelli et al., 2020) . Independently of PIMUZ A/V 461, two specimens exhibit more or less well-preserved mandible remains. PIMUZ A/V 463 and PIMUZ A/V 4150 show mf1 and mf2 less lingually trilobate than in G. reticulatus , and especially their mf3 does not show furrow any in the anterolingual part of their first lobe, supporting an attribution to G. munizi (Cuadrelli et al., 2019) . Apart from osteoderms, postcranial skeletal bones are only marginally diagnostic in differentiating the two species (Cuadrelli et al., 2019, 2020). Teir major difference lies in the size, but this criterion does not seem robust, as it can be impacted by a strong intraspecific size variability, by ontogeny and by sexual dimorphism (see an example in Glyptotherium — Gillette & Ray, 1981; Gillette et al., 2016; Zurita et al., 2018). A recent study shows differences in pelvic girdle between G. jatunkhirkhi Cuadrelli et al., 2020 , and G. reticulatus without addressing these comparisons to G. munizi (Cuadrelli et al., 2020) . Based on the almost complete specimen, PIMUZ A/V 461, I can state that the pelvic girdle of PIMUZ A/V 466 has a much more dorsoventrally extended foramen obturator than in G. reticulatus but without the anteroposterior and dorsoventral extension of the ischial plate known in G. jatunkhirkhi . I hypothesize that this combination of foramen obturator and ischial plate is unique to G. munizi . For the rest of the specimens, our attention is focused on the osteoderms. For PIMUZ A/V 464, PIMUZ A/V 465, PIMUZ A/V 468, PIMUZ A/V 470, PIMUZ A/V 471, and PIMUZ A/V 4142, the osteoderms, or part of them, belong to the dorsal part of the carapace and present the typical rosette ornamentation known for Glyptodon (Cuadrelli et al., 2019; Fernicola & Porpino, 2012). In each of these osteoderms, a relatively flat central figure is surrounded by a line of peripheral figures always smaller than the central figure as in G. munizi . For PIMUZ A/V 469, there are only osteoderms in the lateroventral or posterior part of the carapace, accompanied by isolated conical tubercles of the caudal notch which are exactly similar to PIMUZ A/V 462 and 472 identified as belonging to G. munizi (see above). In conclusion, for all the specimens mentioned in this section, I propose a reattribution to G. munizi rather than to G. reticulatus . With 12 specimens belonging to G. munizi , the emblematic genus Glyptodon is the most represented cingulate species in the Roth collection at PIMUZ. Te presence of an almost complete specimen underlines the strong potential for study of this species, but many other specimens present a relatively high degree of completeness for both cranial and postcranial remains. In recent years, investigations have focused particularly on endocranial structures ( Le Verger et al., 2021; Tambusso & Fariña, 2015b; Tambusso et al., 2021). Te cranial and endocranial anatomy of glyptodonts from the Roth collection at PIMUZ is discussed by Christen et al. (this volume).