Wednesday, 21 December 2011

Remarkable New Fossils Give Great Insight Into The Ordovician Ecosystem

The Cambrian period is best remembered for its great wave of diversification, better known as the Cambrian Explosion. Yet the Ordovician also experienced its own explosion. This second wave of evolutionary innovation created whole new ecosystems inhabited by a new range of organisms. Palaeontologists thought that they had a reasonably complete picture of the Ordovician biota, from tiny invertebrates to giant fish and even whole new animal groups, such as conodonts.

The hydroid fossil from the Llanfawr Quarry
Now remarkable new fossils from Wales have shown that the explosion may have had a far greater impact upon marine diversity than previously thought. A team of palaeontologists, led by Drs Joe Botting, Lucy Muir and Talfan Barnie, were excavating at the disused Llanfawr quarry in Powys, Llandrindod Area, Wales in 2004. They moved to an undisturbed rock face and after a few minutes, Dr Talfan made a remarkable fossil discovery.

X ray analysis revealed the presence of a complete and remarkably well preserved solitary hydroid. What makes this discovery so important is the revelation of a whole new ecosystem. Other fossils including sponges, worms, nautiloids and crinoids showed that the hydroid was from a deep sea community.

'They were found in Llanfawr quarry, an area well-known for its fossils, but somehow the important fossils had been missed', said Dr Muir. 'It's not a discovery that you can point to and say, this proves such-and-such' said Dr Muir. 'Rather, it's a question of adding a large new chunk of knowledge, and in turn suggesting that there are many more chunks left to find. This type of ecological community type was simply unknown from rocks this old, and for it to suddenly appear makes palaeontologists wonder what else they've been missing.

It shows us that Ordovician ecosystems were even more diverse and complicated than we imagined. Using geological evidence, the team came to the conclusion that the whole of Llandrindod area was once an ocean dotted by a series of volcanic island arc chains. The fine ash from the eruptions would have buried the deep sea organisms, preserving them in perfect detail. This type of preservation is very similar to that shown in the remarkable Charnia fossils from Mistaken Point.