Irish scientists lead discovery of 350m-year-old fossil sea urchins

29 Nov 2022

Scientists removing fossil sea urchins at Hook Head. Image: University of Galway

The fossil find has the potential to reveal important information about the nature of seafloor communities during the Carboniferous period.

Scientists from University of Galway have discovered a group of fossil sea urchins on the coast of south-east Ireland.

The discovery is a hugely significant one for Irish palaeontology. The fossils were discovered preserved on a limestone surface near the shore on the Hook Head peninsula in Co Wexford.

The fossil sea urchins still have their spines attached, which is unusual as these typically fall away when the creature dies. Researchers said the sea urchins appear to have died together on the seafloor almost 350m years ago.

The group of 200 fossils occupied a very small part of the rocky surface at Hook Head that was in danger of being lost to coastal erosion.

A team of scientists, led by researchers at University of Galway’s School of Natural Sciences, recovered the specimens.

A close-up view of the Hook Head fossil sea urchins where their spines are visible.

The fossil sea urchins. Image: University of Galway

The discovery of the fossils was first made by Dr Nidia Álvarez-Armada.

“I initially discovered these fossil sea urchins on a rocky coastal outcrop when I was surveying the geology of Hook Head peninsula for my undergraduate bachelor of science thesis at University of Galway.”

She said she was “completely astonished by both the sheer number of fossil specimens present and also their exceptional preservation”.

“The significance of the find was instantly apparent and I immediately began mapping and recording the shape, size and position of each individual urchin on the rock surface. This work took several weeks to complete, but it was important to carefully document the fossil find in as much detail as possible.”

The research team has said that the fossil find has potential to reveal important information about the nature of seafloor communities during the Carboniferous period, which occurred around 354m to 290m years ago.

The discovery site is protected under law and approval for the recovery of the fossils was granted by several State agencies as well as the local landowner. Following the successful removal of the fossils, the team entrusted the piece of rock to the National Museum of Ireland for conservation and further study.

The discovery and recovery of the fossils was reported in the Irish Journal of Earth Sciences, which is published by the Royal Irish Academy.

One of the scientists who peer-reviewed the paper called the discovery one of the “most exceptional and striking fossil finds in the last century”.

Dr John Murray from the School of Natural Sciences at University of Galway added: “The significance of this discovery was such that all of the members of the rescue team willingly volunteered their time and expertise to travel to Hook Head to help salvage the fossil-bearing slab.”

Murray supervised Álvarez-Armada’s project and co-authored the study. “The Hook Head urchins must have been buried quite quickly after they died, with little or no post mortem disturbance. However, it remains unclear why they congregated in such large numbers at this location on that ancient seafloor,” he said.

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Blathnaid O’Dea is Careers reporter at Silicon Republic