Galápagos Chimaera

This ghostshark has a compressed, elongate body, which thins out to its tail. It is medium-brown in color, with a lighter underside and a darker upperside. Most of its fins are dark, including its two dorsal fins, while its lower tail is white. It is covered with blotches of white, which can be circular, narrow, or elongate in shape. Of the two type specimens, the holotype had a total length (TL) of 38.1 centimetres (15.0 in) and a body length (BDL) of 21.1 centimetres (8.3 in), while the paratype was slightly smaller, with a TL of 22.7 centimetres (8.9 in) and BDL of 10.7 centimetres (4.2 in). The species has smooth skin and lacks scales. It has two dorsal fins, the first of which is upright and triangular and the second of which is longer and lower. The end of its tail fin has a "whip-like" fiber at the end of it and it lacks an anal fin. It has three pairs of plates inside of its mouth for teeth. Males have multi-pointed external sex organs. Other characteristics of the species include a small head, a round snout, large green eyes, and nostrils linked to its mouth with a flap-covered groove.

H. mccoskeri is likely endemic to the Galápagos Islands in the southeastern Pacific Ocean. When the species was described in 2006, there were nine recorded instances of it at four locations: Fernandina Island, Española Island (paratype), Marchena Island, and San Cristóbal Island (holotype). The species' population is unknown. Most fisheries in its range operate in shallower waters than its preferred depth; no deepwater fisheries are present in its range. Its habitat cannot be trawled in because it is too rocky. Its entire range is within the Galápagos Marine Reserve; in the reserve, industrial fishing is prohibited, but artisanal fishing is still allowed. Fishers frequently violate these regulations, fishing illegally, and they are often not prosecuted for such activities. The International Union for Conservation of Nature (IUCN) said that the species requires further studying of its population and threats before receiving an assessment. It is listed as least concern on the IUCN Red List.

== References ==

The Galápagos ghostshark has been observed to occur on steep slopes, in areas containing stones and boulders with dispersed sand and silt. The nine specimens in the original description were found in depths of 396.25–505.97 metres (1,300.0–1,660.0 ft). This is a shallower range than most species in Hydrolagus, but the two most closely related species to the Galápagos ghostshark – the spotted ratfish (Hydrolagus colliei) and the dark ghostshark (Hydrolagus novaezealandiae) – do live in shallower depths. The specimens were found close to the sea floor, in groups or alone. The species is a carnivore, feeding on aquatic worms, mollusks, and crustaceans.