Evolution and development of the jaw adductor chamber in turtles

Abstract

Turtles have a primarily anapsid skull, which was modified several times during the evolution of crown-Testudines, resulting in reductions of skull covering called emarginations. Many factors have been suggested to explain the origin and function of those, such as the jaw adductor musculature arrangement. Similarly, all Testudines have an enlarged otic capsule that reduces the space inside the adductor chamber and affects the course of the fibres of jaw muscles. This resulted in the origin of two independent trochlear mechanisms in this lineage that deflects the jaw adductor musculature around the enlarged otic chamber. Also, in pleurodires (Testudines) a novel structure in the pterygoid bone, the cavum pterygoidei, modifies the arrangement of the jaw adductor muscles in this region. The goal of this project is to understand the origin and evolution of those structures in the adductor chamber of turtles, integrating morphological, embryological, histological and paleontological data providing a more holistic understanding of the subject. The purpose of this internship is to develop the ontogenetic and to complement the paleontological aspects of the initial project at Dr. Ingmar Werneburg's laboratory, at the Universität Tübingen, Germany. During the internship the candidate will analyze histological material and do dissections in conjunction with Dr. Werneburg, and also visit European collections with fossil turtles. This will be of great importance for his academic development, setting collaborative partnerships and strengthen the field of research in vertebrate morphology in Brazil. (AU)