PRELIMINARY REPORT OF ABELISAURID (DINOSAURIA, THEROPODA) TOOTH AND TOOTH ATTACHMENT TISSUES

Abstract

Abelisauridae is a group of Late Cretaceous Gondwanan theropods characterized by their bizarre skull anatomy, including a short,
high, and conspicuously fused cranium ornamented with a rugose external surface. Studies of abelisaurid teeth have primarily focused on external crown morphology, leaving aspects of the microstructure of teeth and their attachment tissues (i.e., periodontium) largely unexplored. These kinds of analyses are essential to a more complete understanding of dental anatomy, development, and evolution in theropod dinosaurs. In this contribution, we study the microstructure of the tooth and periodontium of an undetermined abelisaurid (MUCPv-1151) from the Upper Cretaceous of Argentina. The histological analysis of a lower jaw fragment revealed the presence of enamel, dentine with distinct growth lines, and cementum in the teeth and alveolar bone lining each alveolus. Although the dental microstructure is comparable to that described for other theropod dinosaurs, there is significant variation in the thickness of the growth lines in the dentine. Regarding periodontium histology, the data indicate that abelisaurids had a gomphosis-type implantation, with a tissue distribution comparable to that of other saurischians, including other non-avian theropods. However, differences were identified in the thickness of the cellular cementum and the degree of development of Sharpey’s fibers in the cementum and alveolar bone. Histological data reveal that the pattern of tooth formation and replacement in abelisaurids is comparable with that of other amniotes. This contribution reveals that, irrespective of cranial specializations reported for abelisaurid theropods, their tooth and periodontium, alongside the pattern of tooth formation and replacement, exhibit highly conservative patterns.