Full text
| |
| Author(s): |
Marcelo Garrone Esteves
Total Authors: 1
|
| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) |
| Defense date: | 2010-08-05 |
| Examining board members: |
Miguel Trefaut Urbano Rodrigues;
Marta Maria Antoniazzi;
Luis Fábio Silveira
|
| Advisor: | Hussam El Dine Zaher |
| Abstract | |
The Squamate mandible is formed by two hemimandibles each one composed of several bones. In the posterior region, the hemimandibles are connected to the skull by the quadrate bone. In the anterior region these are connected to each other by the mandibular symphysis, which has an important anatomical role, limiting the independent movement of the hemimandibles. Several authors noted the existence of morphological variation in the mandibular symphysis, but only a few detailed studies were made about this structure, the majority of them focusing on Serpentes. These authors claim the lizards and the Scolecophidia snakes possess a rigid mandibular symphysis while the mosasaurs and the rest of the snakes would possess a free mandibular symphysis. The free symphysis is one of the characters used by several authors to support the existence of the Pythonomorpha clade formed by the mosasaurs and the snakes, the existence of this clade is questioned by several authors that believe the presence o the free symphysis to be a convergence in this two groups. Contrary to what was expected, the connection of Meckels cartilages were absent in several lizards families while it was present in only one scolecophidian family. The loss of Meckels cartilages connection would be the first step to the formation of a free symphysis, its occurrence in several families reinforces the hypothesis that the free symphysis could have evolved independently in the mosasaurs and the Alethinopidia snakes. Based on the morphologies observed in this study it was also possible determinate the steps necessary for the evolution of a free symphysis. (AU) | |
| FAPESP's process: | 07/52222-6 - Morphological analysis of the mandibular symphysis in the clado Squamata |
| Grantee: | Marcelo Garrone Esteves |
| Support Opportunities: | Scholarships in Brazil - Master |