On the dentition, tooth replacement, and taxonomic status of Charruodon tetracuspidatus Abdala & Ribeiro, 2000: A bizarre cynodont from the middle upper Triassic of southern Brazil

Abstract

Among the living tetrapods, mammals present a unique tooth replacement pattern, diphyodonty. Therefore, studying the dentition of mammalian ancestors is relevant to a better understanding of how this remarkable feature evolved. However, little is known about the postcanine tooth replacement pattern among Triassic cynodonts. Here, we applied the nondestructive method of microcomputed tomography (microCT) to analyze the dentition of the enigmatic Upper Triassic sectorial‐toothed cynodont Charruodon tetracuspidatus (MCP 3934 PV, holotype) from the Candelaria Sequence, Santa Maria Supersequence, Brazil. The microCT‐scan data allowed visualization of the replacement dentition and roots of the functional teeth, which provided information to inform interpretations of the ontogenetic stage and taxonomy of the species. A combination of dental and mandibular traits, as well as the small size of the specimen MCP 3934 PV, suggest an early ontogenetic stage. Additionally, the specimen could potentially be an ontogenetically immature form of another taxon, or a yet unknown species of probainognathian cynodont. Therefore, Charruodon tetracuspidatus is here designated as a nomen dubium, given the challenges of maintaining the species as valid.

The dawn of an Era: New contributions on comparative and functional anatomy of Triassic tetrapods

“…Furthermore, they conduct a phylogenetic analysis, positioning A. gassenae as the sister group to Prozostrodontia, thus shedding light on its evolutionary relationships within the broader context of cynodonts. Hoffmann et al (2024, this issue) reanalyze the mandibular anatomy of a highly enigmatic Brazilian Carnian cynodont, Charruodon tetracuspidatus . This taxon has long puzzled researchers due to its uncertain phylogenetic position within the probainognathian group.…”