The spongehead catshark (Apristurus spongiceps) is a rare species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of deep-sea catshark

Catshark

Catsharks are ground sharks of the family Scyliorhinidae, with over 150 known species. While they are generally known as catsharks, many species are commonly called dogfish....

, family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Scyliorhinidae. This species was only known from two specimens taken in the Pacific Ocean

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

: an adult

Adult

An adult is a human being or living organism that is of relatively mature age, typically associated with sexual maturity and the attainment of reproductive age....

 from near Bird Island

Nihoa

Nihoa , also known as Bird Island or Moku Manu, is the largest and tallest of ten islands and atolls in the uninhabited Northwestern Hawaiian Islands . The island is located at the southern end of the NWHI chain, southeast of Necker Island...

, Hawaii

Hawaii

Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

, and a juvenile

Juvenile (organism)

A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...

 from the Banda Sea

Banda Sea

The Banda Sea is a sea in the Maluku Islands of Indonesia, technically part of the Pacific Ocean but separated from it by hundreds of islands, as well as the Halmahera and Ceram Seas...

 off Sulawesi

Sulawesi

Sulawesi is one of the four larger Sunda Islands of Indonesia and is situated between Borneo and the Maluku Islands. In Indonesia, only Sumatra, Borneo, and Papua are larger in territory, and only Java and Sumatra have larger Indonesian populations.- Etymology :The Portuguese were the first to...

. They are found on or near the bottoms of insular continental slopes, at a depth of 570 to 1,480 meters. In 2002, the spongehead catshark was seen alive in its natural habitat for the first time, from the submersible

Submersible

A submersible is a small vehicle designed to operate underwater. The term submersible is often used to differentiate from other underwater vehicles known as submarines, in that a submarine is a fully autonomous craft, capable of renewing its own power and breathing air, whereas a submersible is...

 Pisces IV at a depth of about a kilometer, on the Northampton Seamount off the northwestern Hawaiian Islands

Hawaiian Islands

The Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll...

.

The spongehead catshark has a thick body

Body

With regard to living things, a body is the physical body of an individual. "Body" often is used in connection with appearance, health issues and death...

 and head

Head

In anatomy, the head of an animal is the rostral part that usually comprises the brain, eyes, ears, nose and mouth . Some very simple animals may not have a head, but many bilaterally symmetric forms do....

 with a moderately long, broadly rounded snout

Snout

The snout, or muzzle, is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw.-Terminology:The term "muzzle", used as a noun, can be ambiguous...

. The five pairs of gill slit

Gill slit

Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of Cartilaginous fish such as sharks, rays, sawfish, and guitarfish. Most of these have five pairs, but a few species have 6 or 7 pairs...

s are very small, and the septa

Septum

In anatomy, a septum is a wall, dividing a cavity or structure into smaller ones.-In human anatomy:...

 between them are covered with unique pleats and folds that extend above and below, over the throat

Throat

In vertebrate anatomy, the throat is the anterior part of the neck, in front of the vertebral column. It consists of the pharynx and larynx...

. The eye

Eye

Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...

s are small and the nostril

Nostril

A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...

s are broad, with slit-like incurrent and excurrent openings. The mouth

Mouth

The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....

 is long, large, and broadly arched, bearing prominently expanded dental bands. There are two dorsal fin

Dorsal fin

A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

s of about equal size; the pectoral fins are rather small while the pelvic fins are high and broadly rounded. The anal fin is short, high, and rounded. The caudal fin is moderately broad. The dermal denticles are closely set and give the skin

Skin

-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...

 a fuzzy or felt

Felt

Felt is a non-woven cloth that is produced by matting, condensing and pressing woollen fibres. While some types of felt are very soft, some are tough enough to form construction materials. Felt can be of any colour, and made into any shape or size....

-like texture. It is dark brown, without fin markings.

The adult holotype

Holotype

A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...

 measured 51.4 cm long and the juvenile measured 10.5 cm long. The juvenile was more slender than the adult but shared the same distinctive pleated gills. As the holotype was a gravid female, the spongehead catshark is likely oviparous. The spongehead catshark belongs to the spongiceps species group within Apristurus, characterized by a short, wide snout, 7-12 valves in the spiral

Spiral valve

A spiral valve is the lower portion of the intestine of some sharks, rays, skates and bichirs. A modification of the ileum, the spiral valve is internally twisted or coiled to increase the surface area of the intestine, to increase nutrient absorption....

 intestine

Intestine

In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...

, the upper labial furrows subequal to or shorter than the lower furrows, and a continuous supraorbital sensory canal.