The recent catch of a frilled shark (Chlamydoselachus anguineus) by researchers off the coast of Portugal has once again dragged this prehistoric marine monster out of the ocean depths and into the limelight. It is not the first time this species, mostly unchanged from 80 million years ago, has been spotted, but its appearance is rare enough to make headlines now (it was once upon a time responsible for sea serpent legends too, perhaps).

Frilled Shark
A frilled shark in the Awashima Marine Park in Shizuoka, south of Tokyo, January 2007. Flickr/Ibolya

It is the frilled shark’s gills that give it its name. The gills have frilly edges, and the first gill slit runs continuously across the shark’s throat, making it unique among sharks to have this physical characteristic.

Frilled Shark Gills
The frilly gills of the frilled shark give it its name. Wikimedia Commons/OpenCage

Another unusual bodily trait the frilled shark exhibits is its jaws, which end where its head ends. In most sharks, the jaws end underneath the head.

Frilled Shark Jaws
The jaws of a frilled shark, unusual among sharks, terminate at the end of its head instead of underneath. Wikimedia Commons/OpenCage

Its mouth has about 25 rows of trident-shaped teeth, approximately 300 of them.

Frilled Shark Teeth
The frilled shark has about 300 teeth in some 25 rows. Wikimedia Commons/OpenCage

Relatively speaking, the frilled shark’s pectoral fins (located just behind the gills) are small. The pelvic fins, often located right behind the pectoral, are located far down the body, along with the single dorsal fin and the anal fin.

Frilled Shark Body
The frilled shark at Aquarium tropical du Palais de la Porte Dorée, Paris, August 2010.

Based on a specimen from Japan, the frilled shark was first described in 1884. In 2007, after being alerted by a fisherman, the Awashima Marine Park in Shizuoka, south of Tokyo, caught a 1.6-meter long (5 feet) female and released a video of the creature.

The frilled shark grows up to two meters in length, and is found across large areas of the Atlantic and Pacific oceans. It usually lives at depths between 600 and 1,000 meters, but has been caught as deep as over 1,500 meters. Since that is too deep for most human activity, and they almost never visit the ocean surface, they are rarely encountered, which could be part of the reason they create a sensation each time one of them is photographed.