‘Living fossil’ thought to be extinct for 273m years rediscovered off Japanese coast – World News

A ‘living fossil’ believed to have gone extinct over 270 million years ago has been found thriving in the depths of the Pacific Ocean.

The strange-looking fossil is formed from the stalks of marine animals, known as crinoids – with corals growing and twisting from them like veins.

The two marine lifeforms – the crinoids, and the hexacoral – used to be well-known for forming a symbiotic relationship, with the coral latched on to its animal host.

But records of the relationship between the two creatures vanished hundreds of millions of years ago, during the Paleozoic era roughly 542 to 251 million years ago.

Now, scientists have found evidence that the mutually beneficial relationship still exists.

A research team has found non-skeletal corals growing from the stalks of marine animals more than 100 metres deep on the floor of the Pacific Ocean, off the coast of Japan.

The joint Polish-Japanese research team, led by paleontologist Mikołaj Zapalski of the University of Warsaw in Poland, have been using stereoscopic microscopy to observe and photograph the specimens.

The research team wrote: “These specimens represent the first detailed records and examinations of a recent syn vivo association of a crinoid (host) and a hexacoral.

“Therefore, analyses of these associations can shed new light on our understanding of these common Paleozoic associations.”

The Paleozoic fossil record is full of countless examples of corals overgrowing crinoid stems to climb above the seafloor into the water column, to stronger ocean currents for filter-feeding.

It is unclear, however, what benefit the crinoids gain from a relationship with coral.

But the research in the journal Palaeogeography, Palaeoclimatology, Palaeoecology has revealed that unlike the Paleozoic corals, the new specimens do not modify the structure of the crinoids’ skeleton.

The scientists have found two different species of coral both growing from the stems of their living crinoid hosts – growing in a bulbous shape from the long, thin stems.

They found that the corals, which attach below the feeding fans of the crinoids, probably do not compete with their hosts for food.

And, being non-skeletal, they are also unlikely to affect the flexibility of the crinoid stalks, although the anemone may have hindered movement of the host’s cirri – thin strands that line the stalk.

If these corals don’t modify the host, and leave no fossil record, the scientists suggest that perhaps they have had a long relationship with crinoids that has simply not been recorded.

This means the modern relationship between coral and crinoid could contain some clues as to Paleozoic interactions between coral and crinoid.

The number of specimens recovered to date is small – but scientists can now do more work to discover the missing history of this “fascinating” fossil friendship.

“The coral-crinoid associations, characteristic of Palaeozoic benthic communities, disappeared by the end of Permian,” the research journal reads.

“This current work represents the first detailed examination of their rediscovery in modern seas.”