MELBOURNE, Australia — What lives a mile under the sea, has tentacles and fins and looks like a decapitated chicken ready for roasting?

The headless chicken monster, of course.

Yes, that is actually the name of a rare creature caught on film this week by researchers working in the Southern Ocean, about 4,000 kilometers, or nearly 2,500 miles, off the southwest corner of Australia.

The “monster” — actually a sea cucumber that helps to filter organic matter on the ocean floor — has been caught on film only once before, last year in the Gulf of Mexico.

Floored by its unusual physique, scientists call it the headless chicken monster. (It is also known as the swimming sea cucumber, the Spanish dancer and by its scientific name — Enypniastes eximia.)