A neomorphic ossification of the nasal cartilages and the structure of paranasal sinus system of the glyptodont Neosclerocalyptus Paula Couto 1957 (Mammalia, Xenarthra)

Abstract

Glyptodonts together with armadillos, pampatheres and peltephilines constitute the Cingulata, one of the three clades of the Xenarthra. The most remarkable feature of this group is the presence of an armored exoskeleton along the head, body and tail. Only a few contributions have described in detail the endoskeleton. In the case of the skull, almost no attention has been focused on the narial region. The objective of this study is to provide a description of the narial anatomy of the glyptodont Neosclerocalyptus. This genus has the most expanded and globular narial region among glyptodonts and was recently described as part of the fronto-nasal sinuses system. Our analysis based on CT scanning shows that this region includes an independent ossification of the nasal cartilage that housed the maxillo-atrioturbinates. This ossification would represent a neomorphic feature produced by a terminal addition of an ossified stage via peramorphosis. Other remarkable anatomical features are the presence of an expanded paranasal sinuses system that involves the nasal, frontal, parietal and squamosal bones, and the wide separation between the maxillo-atrioturbinates and ethmoturbinates. Functional consequences of this rearrangement are not readily predicted or inferred. Thus, this neomorphic ossification would constitute a morphological novelty, but not necessarily a functional one.