''Idiastion'' is a small

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

belonging to the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Scorpaenidae The Scorpaenidae (also known as scorpionfish) are a family of mostly marine fish that includes many of the world's most venomous species. As their name suggests, scorpionfish have a type of "sting" in the form of sharp spines coated with venom ...

, the scorpionfishes. They are found in the

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

and

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

oceans.

Taxonomy

''Idiastion'' was first described as a genus by the American

ichthyologist Ichthyology is the branch of zoology devoted to the study of fish, including bony fish ( Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 33,400 species of fish had been described as of Octobe ...

William N. Eschmeyer in 1965 when he was describing its

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

, ''Idiastion kyphos'', from the southeastern

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

, between Venezuela and Grenada. Subsequently two more species have been added to the genus from the Pacific Ocean. The genus is classified within the

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide usage of the term in English language, English is in the discipline of anthropology. This definition is contested, in p ...

Scorpaenini in the

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...

Scorpaeninae Scorpaeninae is a subfamily of ray-finned fish belonging to the family Scorpaenidae in the order Scorpaeniformes, it includes the scorpionfishes, the lionfishes and turkeyfishes. They bear venomous spines in the anal, dorsal and pelvic fins which ...

of the scorpionfish family Scorpaenidae. The genus name ''Idiastion'' is the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

word meaning "hermit" or "recluse", alluding to the rarity of the scorpionfishes at the depths at which ''Idiastion'' was collected from.

Species

There are currently three recognized

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

in this genus: * ''

Idiastion hageyi ''Idiastion'' is a small genus of marine ray-finned fish belonging to the family Scorpaenidae, the scorpionfishes. They are found in the Atlantic and Pacific oceans. Taxonomy ''Idiastion'' was first described as a genus by the American ichthyolo ...

'' McCosker, 2008(Galapagos humpback scorpionfish) * ''

Idiastion kyphos ''Idiastion'' is a small genus of marine ray-finned fish belonging to the family Scorpaenidae, the scorpionfishes. They are found in the Atlantic and Pacific oceans. Taxonomy ''Idiastion'' was first described as a genus by the American ichthyolo ...

'' Eschmeyer, 1965 (Sharpcheek scorpionfish) * ''

Idiastion pacificum ''Idiastion'' is a small genus of marine ray-finned fish belonging to the family Scorpaenidae, the scorpionfishes. They are found in the Atlantic and Pacific oceans. Taxonomy ''Idiastion'' was first described as a genus by the American ichthyolo ...

'' Ishida & Amaoka, 1992 (Flame humpback scorpionfish)

Characteristics

''Idiastion'' scorpionfishes have a deep body, deepest behind the head with a hump backed shape. They have well developed, robust spines which can have more than one point. They do not have an occipital pit behind their large eyes which have a suborbital ridge armed with between 5 and 8 spines. There are 4 spines on the preoperculum with the uppermost one being the longest and being located some distance from the other 3 spines. They have small, simple teeth on the jaws and the roof of the mouth. They have 12 spines and 9 soft rays in the

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

and 3 spines and 5 soft rays in the

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

. The

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

has 17-19 rays, the central rays being the longest and the uppermist ray and bottom 7-9 rays are unbranched with the lower ones being fleshy with their tips protruding beyond the membrane. They have a complete

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

with tubes on the scales and a small

swim bladder The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled Organ (anatomy), organ that contributes to the ability of many bony fish (but not cartilaginous fish) to control their buoyancy, and thus to stay at their curren ...

. These scorpionfishes are small fishes with standard lengths ranging from in ''I. kyphos'' and in ''I. pacificum''.

Distribution and habitat

''Idiastion'' scorpionfishes are found in the western Atlantic Ocean (''I. kyphos''), the

Galápagos Islands The Galápagos Islands (Spanish: , , ) are an archipelago of volcanic islands. They are distributed on each side of the equator in the Pacific Ocean, surrounding the centre of the Western Hemisphere, and are part of the Republic of Ecuador ...

(''I. hageyi'') and around Japan and over the

Emperor Seamounts An emperor (from la, imperator, via fro, empereor) is a monarch, and usually the sovereign ruler of an empire or another type of imperial realm. Empress, the female equivalent, may indicate an emperor's wife ( empress consort), mother (empr ...

in the northwestern Pacific (''I. pacificum''). They live close to the bottom over reefs and soft substrates.

References

{{Taxonbar, from=Q1882947 Scorpaenini Marine fish genera Taxa named by William N. Eschmeyer