Rhenopyrgid edrioasteroids © Mr Virgil Tanasa

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Newest member of echinoderm family revealed

A team of researchers at London’s Natural History Museum, led by Dr Tim Ewin, have described a new species of fossil echinoderm from the Silurian period, revealing insights into its ecology and a rather unusual appearance. 

A newly discovered group of well-preserved fossils from Anticosti Island in Quebec, Canada gave the team the chance to learn more about these unusual animals. The investigation revealed fossils to be a new species, now named Rhenopyrgus viviani, that lived 435 million years ago. The extinct echinoderm is a distant relative of the starfish, a group that until now has been surrounded with controversy regarding their skeletal structures, behaviour and evolution.

Dr Ewin explains ‘A big part about understanding early life, such as these Rhenopyrgids from 435 Million years ago, is simply knowing what that life looked like and how they behaved. Being able to accurately reconstruct an animal gives us valuable insights into how it lived and in cases, such as this, they can prove to be quite unique in appearance and have surprising behaviour.’

‘By expanding our knowledge of how animals in the past lived and evolved we can better understand why they became extinct and so protect the biodiversity of our planet today.’

Previously it was thought that these animals were burrow dwellers, able to contract the entire stem into the sediment and hide away. Instead Dr Ewin’s team have reconstructed them as bottom dwelling “mud-stickers” that stand erect. The animals were supported by the insertion of a bulbous sac-like structure at the base of the stem into a muddy sea floor and were only able to contract a small part of the top of the stem to protect important openings such as the anus.

Dr Ewin continues: ‘Rather than living in mud burrows we now believe these unusual looking creatures protruded from the sea floor displaying a degree of flexibility. This allowed them to place their mouth higher up into the water column to feed. It is remarkable how new fossil evidence can alter our perceptions of ancient life’.

The new paper also identified greater diversity in the construction of the mouth of rhenopyrgids than previously thought. This diversity of form has also been seen in other stalked edrioasteroids suggesting convergent evolution of these adaptations.

The paper New rhenopyrgid edrioasteroids (Echinodermata) and their implications for taxonomy, functional morphology and palaeoecology is published in the Journal of Paleontology.

Notes for editors 

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