Investigating the diversity of sea-urchins

Research into sea-urchin fossils collected from Portugal has revealed that diversity of the taxa seems to be linked with the evolution of the sea basin.

Dr Marcello Ruta, from the School of Life Sciences, University of Lincoln, UK, was part of the team which investigated how echinoid (sea-urchin) diversity changed through the Mesozoic period – 252 to 66 million years ago.

They focussed on a comprehensive database of fossil specimens from the Lusitanian and Algarve basins in Portugal.

A long-standing debate in current paleobiological research concerns the significance of global diversity patterns retrieved from raw counts of fossils through time, and numerous quantitative studies of the quality of the fossil record have concluded that fossil diversity is biased by many factors.

In this study, researchers chose to focus on a regionally restricted, but well sampled series of echinoids from Portugal in order to control for certain biases.

The aim was to explore the nature of the Portuguese echinoid fossil record, by investigating the palaeodiversity signal and comparing it with the already documented echinoderm record from the same era from the UK.

The research revealed that the diversity pattern is far from having a defined trend, showing many fluctuations that appear to be linked with gaps in the geological record.

Dr Ruta concluded: “Echinoid diversity during the Mesozoic in the Lusitanian basin is far from having a general trend, differing from previous global studies in other taxonomic groups. Many of the variations in diversity seem to be linked to basinal discontinuities and, therefore, with the evolution of the basin. Furthermore, the temperature and sea level changes appear to have had very little influence on echinoid diversity.”

The study ‘Mesozoic echinoid diversity in Portugal: Investigating fossil record quality and environmental constraints on a regional scale’ is published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.

The fossil sea-urchin Acrosalenia. Photo courtesy: Professor Andrew B. Smith, The Natural History Museum, London
The fossil sea-urchin Acrosalenia. Photo courtesy: Professor Andrew B. Smith, The Natural History Museum, London