Deep sea root of marine evolution sparks controversy

The deep ocean may have played a much bigger role in protecting marine diversity than first thought suggests controversial new research from the University of Portsmouth. Fossils of starfish, sea urchins and snails more than 180 million years old found in the Austrian Alps suggest that a number of animals evolved in the deep sea before spreading to shallow waters. This overturns the widely held belief that deep sea animals evolved from their shallow water ancestors. “Until now, very little was known about the geological history of deep-sea communities,” said Professor Andy Gale from the School of Earth and Environmental Sciences. “These findings are controversial, because it has been widely believed that brief but intense periods of oxygen deprivation and warming caused periodic mass extinction of deep sea animals. Our findings contradict this.” The researchers report the discovery of at least 68 different species of echinoderms, molluscs, brachiopods and crustaceans in the Austrian Alps near Salzburg. Gale, who conducted this research with colleagues in Germany, said that this work sheds light on sea creatures which lived so deep in the ocean that light never reached them. “It appears that darkness and depth protected them and played a much greater role in protecting modern deep-sea biodiversity than previously thought,” Gale said. The research, published in Proceedings of The Royal Society B, suggest that the deep sea was more successful in protecting animals against extinction than shallow, coastal seas, and that deep sea species might be more resilient to extinction than their shallow water counterparts. “The evolutionary processes which shaped the deep-sea are still considered controversial in the scientific world because so little is known about them. However, these new findings provide a unique window into Early Jurassic deep-sea biodiversity,” said Gale. “It seems that once families of some species had colonised the deep sea, they either remained there or became extinct. Occurrences in shallow water of these same families suggests they have sometimes temporarily expanded into shallow waters.” First glimpse into Lower Jurassic deep-sea biodiversity: in situ diversification and resilience against extinction