Eight-Armed Brittle Star with Thousands of Thorny Teeth Amazes Marine Biologists

The origins of an eight-armed, pig-snouted brittle star discovered in the depths of the South Pacific may be traced back to the dinosaur era.

The brittle star, which has a body diameter of only 1.1 inches (3 centimeters) and limbs around 3 inches (8 cm) long, belongs to a brand-new family of starfish cousins that dates back 180 million years to the Jurassic period.

Hiding Deep Underwater

The brittle stars might be hiding in a deep environment that hasn't altered much in millions of years, ranging from 1,180 feet to 1,837 feet (360 to 560 meters). According to research leader Tim O'Hara, invertebrate curator at Museums Victoria in Melbourne, Australia, the tropics at this depth appear to be suitable for uncovering evolutionary relics or surviving species of extremely old groupings of creatures.

"This is presumably due to the fact that tropical ecosystems are incredibly ancient, dating back to the dinosaur era, and haven't altered much," O'Hara said to Live Science. "As a result, some of these 'living fossils' are able to survive until our time."

Discovery

The brittle star was discovered by O'Hara in a barrel of unidentified specimens at the French National Museum of Natural History in Paris in 2015. The specimen was obtained in New Caledonia, a French territory in the South Pacific, in 2011.

Collecting Samples

After scientists used a huge net known as a beam trawl to collect samples from the bottom of a volcanic ridge known as Banc Durand, the new brittle star was discovered. The specimen was unusual in that it had eight arms instead of the usual five or six for brittle stars. On the bottom of its body, it possessed long jaws bristling with teeth. Its arms featured an unusual skeletal structure as if they were made up of dozens of small pig snouts fused together.

"I could see right away that it was different from all the other brittle stars I was gazing at," O'Hara said.

O'Hara and his colleagues discovered the brittle star was not closely linked to known species of echinoderms, the group that comprises previously known brittle stars, starfish, and other symmetrical bottom dwellers like sand dollars, after decoding the specimen's DNA.

Pig Snouted Patters

That's when paleontologist Ben Thuy of the Luxembourg National Museum of Natural History realized he'd seen the strange pig-snouted pattern on the brittle star's limbs before. He couldn't figure out why they seemed familiar at first. Still, then he noticed a remarkably identical image of fossils discovered in northern France that he had put on a scientific poster years earlier, O'Hara said.

Ancient Species

The brittle star has ancestors dating back 180 million years when the supercontinent Pangaea was splitting up and opening new waters because of physical similarities. To suit these new species, the researchers formed a new family called Ophiojuridae. The term is derived from the ancient Greek word "ophio," which means "serpent," and the Jura Mountains in Europe, where the Jurassic geology was originally described.