ratfishes

Ratfishes, commonly known as chimaeras or ghost sharks, are a lineage of cartilaginous fishes in the order Chimaeriformes, within the subclass Holocephali. They are distant relatives of sharks and rays and represent an ancient branch of vertebrate evolution. The name ratfish derives from their elongated, sensitive snout.

Anatomy: Ratfishes have a cartilaginous skeleton, a broad head with a long, tapering snout, and large pectoral fins. The mouth is located on the underside and bears tooth plates that function like grinding surfaces to crush shelled prey. Their skin is generally smooth or with small ridges, and they possess several pairs of gill openings on the sides of the head, often covered by a soft protective flap in many species.

Distribution and ecology: They inhabit temperate and some tropical oceans, many living on the continental shelf and slope, from shallow to deep waters, often at depths of hundreds to thousands of meters. They are slow-moving, bottom-dwelling predators and scavengers, feeding on mollusks, crustaceans, and echinoderms.

Reproduction and conservation: Most species are oviparous, laying large leathery eggs in protective cases on the seafloor. Chimaeriformes have internal fertilization with males bearing claspers. They mature slowly and have low fecundity, making them vulnerable to overfishing. They are rarely the target of fisheries but are frequently bycatch in deep-sea trawls. The group includes about 50 living species.