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Evolution of axial skeleton diversity in reptiles

Evolution of axial skeleton diversity in reptiles

Supervisor: Dr Jason Head

Co-supervisor: Dr Rob Asher

Project summary:

The axial skeleton is a key innovation in the diversification of form and function in vertebrates, and developmental studies have revealed molecular mechanisms that pattern vertebral and rib anatomy in model taxa. The roles of development in driving macroevolutionary innovations in axial skeletal morphology across phylogeny are less understood, and the evolution of skeletal diversity is poorly known for many vertebrate lineages. Reptilia is a diverse group of over 20,000 living species with a wide range of axial specializations from turtle shells to the vertebral columns of snakes and birds. The evolution of axial anatomies across the clade has not been comprehensively examined in the context of developmental mechanisms or environmental histories, however.

We will reconstruct evolutionary patterns of anatomical change and innovation in the axial skeleton in all major reptile clades, including fossil taxa such as dinosaurs, pterosaurs, and marine reptiles. We will use phylogenetic comparative methods to compare anatomical patterns with developmental data from model taxa, allowing the inference of evolutionary histories of regulatory gene function in the origin of new axial morphologies. We will use fossil data to place results in the contexts of radiation, extinction, and environmental change through deep time.

What the student will be doing:

The student will formulate hypotheses on the history and mechanisms underlying the diversification of reptile axial skeletal morphology by collecting data on vertebral and rib morphology in modern and fossil reptiles through examination of museum collections, including Computed-Tomographic (C-T) and surface scanning techniques. The student will use geometric morphometric analysis of anatomical shape to quantify changes in the axial skeleton both within and between taxa, and will use phylogenetic comparative methods to reconstruct ancestral states, calculate rates of change, and to examine historical patterns of anatomical and developmental change. 

References:

Head, J. J., and P. D. Polly. 2015. Evolution of the snake body form reveals homoplasy in amniote Hox gene function. Nature, 520:86-89. doi: 10.1038/nature14042.

Müller, J., T. Scheyer, J. J. Head, P.M. Barrett, P. Ericson, D. Pol, and M. R. Sanchéz-Villagra. 2010. The evolution of vertebral numbers in recent and fossil amniotes: The roles of homeotic effects and somitogenesis. Proceedings of the National Academy of Sciences of the United States of America (PNAS), 107:2118-2123

Funding:

Applicants may apply to the NERC DTP for funding for this project.