Evolutionary history of tooth attachment systems in Archosauromorpha: understanding the origin and ontogeny of archosaurian thecodonty

• Grant number: 22/12395-9
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: May 01, 2023
• End date: April 30, 2024
• Field of knowledge: Biological Sciences - Zoology - Paleozoology
• Principal Investigator: Max Cardoso Langer
• Grantee: Gabriel Mestriner da Silva
• Supervisor: David Christopher Evans
• Host Institution: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
• Institution abroad: University of Toronto (U of T), Canada
• Associated to the scholarship: 22/00171-9 - Evolutionary history of tooth attachment systems in Archosauromorpha: understanding the origin and ontogeny of Archosaurian thecodonty, BP.DR

Abstract

The recently published paper of Mestriner et al. (2022) challenged the idea that Silesauridae had a simple permanent ankylothecodont dentition, because their teeth spend considerable time attached to the jaws via a non-mineralised periodontal ligament (gomphosis) prior being fused in place. This condition is known as "delayed ankylosis", with teeth passing through an extended stage in which the teeth are suspended in sockets by soft periodontal ligament, followed by posterior mineralization and fusion to the jaw. The tooth attachment development in silesaurids could be a promising model to understand the ancestral condition in the sister group of dinosaurs and, possibly, crocodylians. Yet, a broader study of dental tissues is necessary to evaluate the evolution of tooth attachment in Archosauromorpha, testing whether heterochrony is responsible for the emergence of a permanent gomphosis stage in crocodylians and dinosaurs or not. In any case, a transition from ankylothecodonty to thecodonty appears to be an oversimplification of a more complex evolutionary history. In recent years, a lot of information regarding tooth attachment in early archosaurs, non-archosaurian archosauromorphs, and non-dinosaurian Dinosauromorpha entered the literature without the required support of histological studies. For this BEPE project, the applicant aims to investigate the evolutionary history of the "archosauromorph tooth attachment system" (ATAS) using traditional histology and micro-computed tomography of tooth-bearing bones reconstructing the ancestral tooth attachment over major archosauromorph clades. The proposal is the first histology-based research to sample a large variety of such reptiles, focusing to clarify the fundamental shifts from the plesiomorphic ankylosis to the gomphosis of Crocodylomorpha and Dinosauria. Moreover, this research also intends to explore the functionality of the dental ontogenetic phases in Archosauromorpha. The Vertebrate Paleontology Section at the Royal Ontario Museum bears a rare-sample thin sectioning and paleohistology lab eqquiped with powerful microscopes, which makes the University of Toronto very placed to support and supervise this project. Additionally, a supervised exchange experience with Dr. Evans will be extremely fruitful in bringing the beneficiary's project into a wider specialist network and to get him in contact with experts on new paleontological techniques. (AU)