Assessing the diversity of hidden dental morphology in Hyperodapedontinae rhynchosaurs (Archosauromorpha, Rhynchosauria)

ABSTRACT

The Hyperodapedontinae taxa are mainly diagnosed by characters from the maxillomandibular apparatus. Here we report two Hyperodapedon specimens from Brazil with apically serrated teeth crowns, which led to the identification of one new non-conical maxillary tooth morphotype, Sh, and the first records of serrated teeth in Rhynchosauria. The known types of pyramidal crowns are here expanded to three morphotypes (P¹, P², P³). Flutes, only reported for Hyperodapedon huxleyi (India), were identified in Hyperodapedon sp. and Teyumbaita sulcognathus (Brazil). Using qualitative and morphometric geometric approaches, we investigated whether the maxillary crown morphology is taxonomically informative or reflects ontogeny. The qualitative analysis demonstrated that crown morphology is not taxonomically constrained. The geometric morphometric analysis revealed that the maxillary crown shape varies according to the relative size and form of the tooth plate, parameters related to ontogeny. Flutes and serrations are recorded in Carnian hyperodapedontines from Brazil and India, a restrained paleolatitudinal range of Gondwana. The lack of information concerning dental ornamentations in other hyperodapedontines from the same latitudinal belt (e.g. Argentina) should be due to the scarcity of more detailed studies focused on crown morphology. Our results open the possibility for further studies focusing on hidden details of Rhynchosauria dental morphology.

KEYWORDS:

• Dentition
• serrations
• flutes
• ontogeny
• Late Triassic
• Gondwana

Acknowledgments

We thank Cesar L. Schultz and Felipe L. Pinheiro for access to collections of UFRGS and UNIPAMPA, respectively. This study was financed, in part, by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (CAS nº 131528/2019-0; MBS nº 307938/2019-0). MBS was also supported by Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro - FAPERJ (E-26/010/002540/2019; E-26/201.066/2021). We thank Léo A. Hartmann for suggestions of improvements on the text.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico [131528/2019-0]; Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro [E-26/010/002540/2019].