Comparative anatomy and phylogeny of post Paleozoic Asteroidea (Echinodermata)

Asteroidea (also called sea stars or starfish) is a clade that includes about 2 000 extant and 600 extinct species. During the late 80’s, the recognition of key morphological characters shared by all post-Paleozoic taxa led to the recognition of the crown group Neoasteroidea. But despite 30 years of morphological based phylogenetic analysis, and the recent development of molecular approaches, no phylogenetic consensus is being achieved.

Asteroids possess a skeleton made of thousands of skeletal elements, organized in series and morphologically differentiated according to their position and function, just like the bones of a vertebrate. The skeletal elements, called ossicles, are articulated with one another through contact surfaces, connective tissues, and muscles. The skeletal structure is also constrained by the development of the ambulacral system and other soft organs. Thus, the skeleton potentially contains a phylogenetic signal that has only been explored so far for few taxa, both living or fossil.

The primary goal of my PhD is to use morphological data, especially from ossicles anatomy and the skeletal structure, to rigorously reconstruct the phylogeny of Neoasteroidea. The use of ossicles anatomy not only allows to define new characters, but also to integrate extant and extinct taxa. Phylogenetic analyses will be developed for major asteroid clades (Focipulatida, Velatida, Paxillosida).