Living Fossil from the Dinosaur Era Discovered in Pacific Ocean

Living Fossil from the Dinosaur Era Discovered in Pacific Ocean

An eight-armed brittle star with pig-snouts was discovered in the depths of the South Pacific ocean. The creature has roots that go back to the days of the dinosaurs.

The brittle star is just 1.1 inch in diameter, and its arms are approximately 3 inches long. It represents a completely new family of these starfish relatives — one with members dating back 180 million years, all the way to the Jurassic Period.

The brittle stars lurk in an environment 1,180 feet to 1,837 feet below the surface that hasn’t changed much in millions of years. The tropics at this depth seem to be a ripe spot for discovering evolutionary relicts, or surviving species of very old groups of organisms, said study leader Tim O’Hara, invertebrate curator at Museums Victoria in Melbourne, Australia.

“This is probably because tropical environments are very old, dating back to the dinosaur era, and haven’t changed much,” O’Hara said. “This allows some of these ‘living fossils’ to persist into our time.” 

O’Hara discovered the brittle star in 2015, in a barrel of unidentified specimens stored in the French National Museum of Natural History in Paris. The specimen was collected in 2011, during an expedition to New Caledonia, a French territory in the South Pacific. Scientists used a large net called a beam trawl to take samples from the seafloor of a volcanic ridge named Banc Durand.

The specimen was unusual, as it had eight arms instead of the typical five or six on brittle stars. It also had long jaws on the underside of its body, bristling with teeth. Its arms also had an odd skeletal pattern that looked as if they were built from dozens of tiny pig snouts snapped together.

“Even from the first look, I could see that it was different from all other brittle stars that I was looking at,” O’Hara said.

After sequencing the specimen’s DNA, O’Hara and his colleagues realized the brittle star was not closely related to any known species of echinoderms, the group that includes previously known brittle stars, starfish and other symmetrical bottom dwellers, such as sand dollars.

That’s when study co-author Ben Thuy, a paleontologist at the Luxembourg National Museum of Natural History, realized he’d seen the bizarre pig-snouted pattern on the brittle star’s arms before. At first, he couldn’t figure out why they seemed familiar, O’Hara said, but then he saw a strikingly similar photograph of fossils found in northern France that he had put on a scientific poster years before.

The similarity revealed that the brittle star had relatives dating back 180 million years, when the supercontinent Pangea was breaking up and forming new oceans. The researchers created a new family, which they named Ophiojuridae, to fit these new species. The name comes from “Ophio,” the ancient Greek word for “serpent,” and from the Jura Mountains in Europe, where the geology of the Jurassic was first defined.

They named the living species Ophiojura exbodi, with “exbodi” referring to the acronym for the scientific expedition that discovered the brittle star.

Perhaps the most interesting part of the brittle star is the way it feeds. It extends its arms into the water to capture plankton such as tiny shrimps. A layer of mucus covers the arms, allowing it to stick to prey. Additional spiky projections on the arms act like meat hooks to grasp passing plankton, O’Hara said. Rows and rows of sharp teeth are then probably used to shred the prey, he said.

The research appeared on June 16 in the journal Proceedings of the Royal Society B. New Caledonia is still being surveyed, according to O’Hara. This raises hopes that this won’t be the last dinosaur-era living fossil found in the region. 

Science News