Neosclerocalyptus pseudornatus Ameghino, 1889

Verger, Kévin Le, 2023, Xenarthrans of the collection of Santiago Roth from the Pampean Region of Argentina (Pleistocene), in Zurich, Switzerland, Swiss Journal of Palaeontology (3) 142 (1), pp. 1-39 : 17

Neosclerocalyptus pseudornatus Ameghino, 1889

Referred material: Complete skull, cervical vertebrae, 24 fragments of vertebrae and other undetermined bones: PIMUZ A/ V 439 ( Figs. 4 , 8 ).

Comment: Te diversity of the Hoplophorinae has been long debated and the validity of many genera has been questioned (e.g., Fernicola, 2008; Paula Couto, 1957; Zurita et al., 2007). A large part of the diversity originally attributed to Hoplophorus is now accepted to belong to the Neosclerocalyptinae on the basis of strong differences in cranium and carapace morphology ( Porpino et al., 2010), as it is the case for many specimens from the Pampean region (Zurita et al., 2009b). Currently, only one species of Hoplophorus is accepted as valid from the Pleistocene of Brazil ( Porpino et al., 2010). Te set of specimens from the Roth collection attributed to Hoplophorus must therefore be revised. Te Neosclerocalyptinae are small glyptodonts (~ 300-600 kg) compared to other ‘subfamilies’ from the Pleistocene (Vizcaíno et al., 2011). Tis ‘subfamily’ is the most abundant in the fossil record (Carlini et al., 2008; Zurita et al., 2009a, b), as also it is in the Roth collection at PIMUZ. Species belonging to Neosclerocalyptus exhibit several singular cranial features associated with strong ossification of the nasal cartilage (Zurita et al., 2011). Te variations in snout shape due to this atypical ossification have been used to distinguish the different species belonging to Neosclerocalyptus (Zurita et al., 2011) . PIMUZ A/V 439 exhibits a snout consisting of two bulbs, derived from ossification of the nasal cartilage, with a low narial opening directed anteroventrally. Te organization into two bulbs arranged one above the other is the main autapomorphy of the species N. pseudornatus and would mark a weaker pneumatization of the sinuses compared to other Pleistocene species for which the narial opening is much larger (Zurita et al., 2011). I also note that a nearly identical specimen was illustrated in the work of Zurita et al., (2011; Fig. 2A–D – no collection number specified) in support of the identification of PIMUZ A/V 439 to N. pseudornatus . Because of its exceptional preservation, the skull of PIMUZ A/V 439 could be subject for the study of Neosclerocalyptinae. In the literature, the ‘subfamily’ has been hypothesized to present a specific diversity resulting from anagenesis induced by a potential correlation between the development of nasal cartilage ossification and the increase of aridity during the cooling phases of the Pleistocene (Zurita et al., 2011). Tis hypothesis was challenged by an investigation of the paranasal sinuses and the nasal cavity of several glyptodonts (Fernicola et al., 2012), but this latter investigation was focused on the most derived Neosclerocalyptus paskoensis Zurita, 2002 , which has also the most extensive pneumatization. A study including the other Neosclerocalyptus species should be conducted to test this hypothesis. Te exploration of the endocranial cavities of PIMUZ A/V 439 may provide further insight into this hypothesis and, therefore, for illuminating the evolution of the clade.

Figures

Fig. 4 Plate of crania belonging to the Cingulata from the Roth collection at PIMUZ.The most complete remains illustrated here correspond to the Eutatini and glyptodonts. Scale bar =10 cm

Fig. 8 Plate of mandibles/hemimandibles belonging to the Cingulata from the Roth collection at PIMUZ.The most complete remains illustrated here correspond to the Eutatini and glyptodonts. Scale bar =1 cm