Bumpy orange creature — with five arms — found on ocean floor. It’s a new species

Thousands of feet below the surface of the Atlantic Ocean, a submersible glided through the dark waters. Perched on a nearby seamount was an orange sea creature, its five arms spread wide.

The bumpy animal turned out to be a new species.

Researchers aboard the National Oceanic and Atmospheric Administration ship Okeanos Explorer set out to explore the depths of the Atlantic Ocean with remotely operated vehicles, Christopher Mah wrote in a study published April 3 in the peer-reviewed journal Zootaxa.

During their 2021 expedition, researchers encountered several “pale orange” sea stars, the study said. They collected one sea star and photographed several more.

Mah analyzed the orange sea stars and realized they’d discovered a new species: Rhianastra isosceles, or Rhian’s isosceles sea star.

Rhian’s isosceles sea stars typically have five “sharply triangular” arms, but one animal had six arms, the study said. The sea stars are covered in “coarse, round” bumps.

A Rhianastra isosceles, or Rhian’s isosceles sea star, on a seamount. Photo shared by Christopher Mah
A Rhianastra isosceles, or Rhian’s isosceles sea star, on a seamount. Photo shared by Christopher Mah

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A photo shows the creamy orange new species near some sandy rocks. Mah said he named the new species “isosceles” after its “distinctive triangular arms.”

Rhian’s isosceles sea stars were found at depths of 5,700 to 6,200 feet, the study said.

The new species is part of a new genus, Rhianastra, named for Rhian Waller, a researcher and leader of the expedition that collected the specimen.

“A further species of this genus has been found in the Pacific,” Mah wrote on X, formerly Twitter.

So far, Rhian’s isosceles sea star has only been found on two seamounts in the North Atlantic Ocean, the study said. The seamounts are about 700 miles east of the Delaware coast.

The new species was identified by its body shape, arms, texture and other subtle physical features. The study did not provide a DNA analysis of the new species.

Mah also discovered another new species of sea star, Bathyceramaster kelliottae, and identified several more sea stars that might be new species.

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