Neoselachians (“modern” sharks, skates and rays) are cartilaginous vertebrates with a long evolutionary history (≈250 My). Due to the cartilaginous nature of their skeleton, complete fossils are exceptional and isolated teeth make up the bulk of their fossil record. These teeth possess an enameloid cover, a hypermineralized tissue whose microstructure has been widely used as a taxonomic criterion for the past forty years. However their taxic diversity is disproportionately high when compared to the number of taxa (mostly sharks) explored for enameloid microstructure. As a result, batomorph (skates and rays) tooth microstructure remains very poorly known (which is also true for virtually all stem chondrichthyans).
My PhD project thus deals with an investigation of the batomorph tooth microstructure through paleontology (evolution of the enameloid microstructure through time) and developmental biology (nature of the enameloid matrix, gene expression in the dental tissues…), using two extant models: the small spotted cartshark (Scyliorhinus canicula) and the thornback skate (Raja clavata). This integrative approach is needed to address issues such as i) the homology relationships between shark and ray enameloid microstructure, ii) the ancestral morphology of the enameloid microstructure among neoselachians, iii) the validity of the enameloid microstructure as a taxonomic criterion, iv) address adaptive hypotheses, such as the dietary impact on the enameloid microstructure.
This dual approach also leads me to use a wide range of technique and equipment, from scanning electron microscopy to in-situ hybridizations.
I’m a teaching assistant intervening in the following undergraduate courses: vertebrate comparative anatomy, vertebrate phylogeny and morphofunctional anatomy and invertebrate paleontology.
On the side, I’m also extremely interested in the preparation and articulation of vertebrate skeletal material. Over the years I’ve worked on representatives of every vertebrate group except cyclostomes, and I’m well experienced in a variety of preparation methods. I’m mainly interested in “reptiles”, actinopterygians and chondrichthyans for the challenge they offer (high skeletal complexity or preparation and preservation issues).
My work can be seen online here:
- Enault S, Cappetta H, Adnet S. 2013. Simplification of the enameloid microstructure of large stingrays (Chondrichthyes: Myliobatiformes): a functional approach. Zoological Journal of the Linnean Society 169: 144-155