Morphological evolution of the skull of worm snakes: a comparative study

Description

Blind snakes represent the extant basalmost snakes of the evolutionary radiation of modern snakes and include fully fossorial species with bizarre skeletal traits. Despite their relevant phylogenetic position in the snake tree, little is known about their ontogeny and what it might reveal about the origin of their skull anatomy. In the context of recently proposed phylogenetic relationships two hypotheses were raised about the evolution of worm snakes. On one hand, some authors proposed that they represent very old phenotypes inherited from the last common ancestor of extant snakes. On the other hand, other authors argued on the basis of morphological information that each worm snake group represents an independent specialization for fossorial habits, as a result of miniaturization, deviating considerably from evolutionary trends of snakes.

The aim of this project is to conduct a comprehensive characterization and specific analyses on skull morphology of blind snakes, incorporating ontogenetic data of blind snakes and alethinophidians. Additionally, the first description of the embryonic development of the skull of a worm snake (Epictia australis) will be addressed. Thus, this project will contribute with novel data on the ontogenetic skull changes in different clades of snakes using 3D reconstructions based on micro-CT data. In addition, a morphological and morphometric approach of the development of the skull of blind snakes will allow us to test hypotheses of homology of cranial elements in snakes, to propose developmental patterns for this group, as well as to reveal similarities or differences with respect to the development of alethinophidian snakes and to depict their evolutionary significance. On a broader scale, this project aims to describe the general patterns of skull diversity of snakes, and to elucidate if the blind snakes correspond to derived forms or are a highly plesiomorphic group.

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