The stars are out: a palaeontological perspective on the early evolution of the Asterozoa

Echinoderms are one of the most morphologically distinctive animal phyla, including forms as varied as sea lilies, sea urchins and sea stars. Sea stars and brittle stars are, together, called the Asterozoa, and they represent the most abundant, taxonomically diverse and geographically widespread of all the living echinoderms. They are important seabed ‘engineers’ and are well-known keystone species. The fossil record of asterozoans stretches back around 480 million years to the Ordovician and includes disparate extinct forms which have historically proved challenging to place within the echinoderm tree of life. This continued uncertainty has resulted in significant gaps in our knowledge of the origin and early evolution of the iconic star-shaped asterozoan bodyplan.

In this project, the student will re-examine historical museum specimens from the Ordovician and Silurian Periods, primarily of the UK, in order to piece together the early evolutionary history of the group. The student will use microCT data to reveal the three-dimensional morphology of these fossils for the first time. This will be integrated into a comprehensive phylogenetic dataset encompassing both fossil and extant echinoderms, with morphological and molecular data, providing a new hypothesis for the emergence and diversification of the asterozoan body plan. Finally, the student will produce a time-calibrated evolutionary tree, allowing them to explore how asterozoans diversified across the Great Ordovician Biodiversification Event – one of the most significant and sustained increases in marine diversity in Earth history.

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