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

Blind snakes are the most basal snakes in the evolutionary radiation of modern snakes and comprise completely fossilised species with bizarre skeletal features. Despite their important phylogenetic position in the snake tree, little is known about their ontogeny and what it might reveal about the origin of their cranial anatomy. In the context of recently proposed phylogenetic relationships, two hypotheses about the evolution of worm snakes have been put forward. On the one hand, some authors suggested that they represent very ancient phenotypes inherited from the last common ancestor of modern snakes. On the other hand, other authors argued, on the basis of morphological information, that each worm-snake group represents an independent specialisation in fossorial lifestyles, as a result of miniaturisation that diverges considerably from the evolutionary trends of snakes.

The aim of this project is a comprehensive characterisation and specific analysis of the skull morphology of blind snakes including ontogenetic data of blind snakes and alethinophidians. In addition, the first description of the embryonic development of the skull of a worm snake(Epictia australis) will be tackled. Thus, this project will provide new data on the ontogenetic changes of the skull in different groups of snakes by creating 3D reconstructions based on micro-CT data. In addition, a morphological and morphometric approach to the development of the skull of blind snakes will allow us to test hypotheses about the homology of cranial parts in snakes, suggest developmental patterns for this group, and reveal similarities or differences in relation to the development of alethinophid snakes and their evolutionary significance. More broadly, this project aims to describe the general patterns of cranial diversity in snakes and to clarify whether the blind snakes correspond to derived forms or represent a highly plesiomorphic group.