Deep-sea species might be more resilient to extinction than their shallow-water cousins.

Ben Thuy of the Luxembourg Natural History Museum and his team found fossils of at least 68 different species of molluscs, brachiopods, crustaceans and echinoderms (including relatives of a modern brittle star, Ophiomyces frutectosus, pictured) that lived more than 1,000 metres underwater around 190 million years ago. By comparing the fossils with shallow-living species from the same period, the team found that the deeper species tended to stay and diversify in deep waters, whereas shallow species were more likely to move to greater depths.

Some of the deep-sea species examined are the oldest known representatives of their respective families, implying that they might have originated and evolved in deep water, rather than migrating there from shallower seas as previously thought. The deep ocean could be a stable refuge for marine species, the team says.

Credit: Ben Thuy

Proc. R. Soc. B. 281, 20132624 (2014)