Trichodontidae, the sandfishes, is a small

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

es from the

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Perciformes Perciformes (), also called the Acanthopteri, is an order or superorder of ray-finned fish in the clade Percomorpha. ''Perciformes'' means " perch-like". Among the well-known members of this group are perches and darters ( Percidae), and als ...

. The species in this family are found in the

North Pacific Ocean North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating direction or geography. Etymology The word ''north'' ...

Taxonomy

Trichodontidae was first proposed as a family in 1869 by the Dutch

herpetologist Herpetology (from Ancient Greek ἑρπετόν ''herpetón'', meaning "reptile" or "creeping animal") is a branch of zoology concerned with the study of amphibians (including frogs, salamanders, and caecilians (Gymnophiona)) and reptiles (in ...

and

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, 35,800 species of fish had been described as of March 2 ...

Pieter Bleeker Pieter Bleeker (10 July 1819 – 24 January 1878) was a Dutch medical doctor, Ichthyology, ichthyologist, and Herpetology, herpetologist. He was famous for the ''Atlas Ichthyologique des Indes Orientales Néêrlandaises'', his monumental work on ...

. For a long time the family was thought to be classified within the order

Trachiniformes Trachiniformes is an Order (taxonomy), order of Percomorpha, percomorph bony fish, whose contents are traditionally placed in suborder Trachinoidei of Perciformes. However, Trachiniformes is recovered as polyphyletic in recent large scale molec ...

but in 2000 the family was reclassified by the Russian biologists Mikhail Nazarkin and Olga Voskoboinikova the monotypic

superfamily SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid sequences into known structural domains, especially into SCOP superfamilies. Domains are functional, str ...

Trichodontoidea in the

suborder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized ...

Cottoidei Cottoidei is a suborder of ray-finned fishes which, according to the 5th edition of ''Fishes of the World'', is placed within the order Scorpaeniformes, alongside the scorpionfishes, flatheads, eelpouts, sticklebacks and related fishes. Taxon ...

of the order

Scorpaeniformes The Scorpaeniformes are a diverse Order (biology), order of Actinopterygii, ray-finned fish, including the lionfishes and sculpins, but have also been called the Scleroparei. It is one of the five largest orders of bony fishes by number of spec ...

. Other workers have found that if the Scorpaeniformes, as delimited in the 5the edition of ''

Fishes of the World ''Fishes of the World'' is a standard reference for the systematics of fishes. It was first written in 1976 by the American ichthyologist Joseph S. Nelson (1937–2011). Now in its fifth edition (2016), the work is a comprehensive overview of t ...

'', is not included in the

it renders the Perciformes

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

. These workers retain the Cottoidei as a suborder within the Perciformes but include the zoarcoids and Sticklebacks and allies as the

infraorder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between Family_(biology), family and Class_(biology), class. In biological classification, the order is a taxonomic rank used in the classific ...

s Zoarcales and Gasterosteales while reclassifying most of the superfamilies of ''Fishes of the World'' as

s with the Trichodontidae included in the infraorder Cottales.

Genera and species

The family consists of three

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

genera, two extant and one extinct: * '' Arctoscopus''

Jordan Jordan, officially the Hashemite Kingdom of Jordan, is a country in the Southern Levant region of West Asia. Jordan is bordered by Syria to the north, Iraq to the east, Saudi Arabia to the south, and Israel and the occupied Palestinian ter ...

and Evermann, 1896 ** ''

Arctoscopus japonicus The Japanese sandfish (''Arctoscopus japonicus''), also known as the sailfin sandfish , is a species of fish of the Percomorpha (perch-like) clade in the Order (biology), order Trachiniformes, being one of the two genera in the Family (biology), ...

'' (

Steindachner Franz Steindachner (11 November 1834 in Vienna – 10 December 1919 in Vienna) was an Austrian zoologist, ichthyologist, and herpetologist. He published over 200 papers on fishes and over 50 papers on reptiles and amphibians. Steindachner descri ...

, 1881) (Japanese sandfish) * '' Diaphantes'' Nazarkin & Voskoboinikova, 2000 ** ''

Diaphantes tilesii ''Diaphantes'' is an Extinction, extinct genus of marine ray-finned fish belonging to the Family (biology), family Trichodontidae, the sandfishes. Its only species, ''D. tilesii'', was found in the Middle Miocene-aged Agnevo Formation of Sakhalin ...

'' Nazarkin & Voskoboinikova, 2000 * '' Trichodon'' Tilesius, 1813 ** '' Trichodon trichodon'' ( Tilesius, 1813) (Pacific sandfish) means extinct

Characteristics

Trichodontid sandfishes are characterised by being small deep, highly compressed bodies with an overall silvery colour. They have a large oblique, upward pointing mouth which has 2 or 3 rows of small sharp teeth on the jaws and

vomer The vomer (; ) is one of the unpaired facial bones of the skull. It is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right maxillary bones. The vomer forms ...

. There is a fleshy fringe on the lips. There are 5 obvious spines on the

preoperculum This glossary of ichthyology is a list of definitions of terms and concepts used in ichthyology, the study of fishes. A B C ...

. They have 2

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

s, the first dorsal fin contains between 8 and 16 spines and is clearly separated from the second dorsal fin which may have a single spine, or none, and between 12 and 20 soft rays. The

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

may hold a single spine, or there may be none, and also has between 28 and 32 soft rays. The large caudal fin is either forked or truncate and the pectoral fins are large and fan-shaped, these fins extend to the middle of the vent and have 21-27 thickened fin rays. The

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

s are located on the thorax and contain a single spine and 5 soft rays. There is a single pair of tube-like nostrils and these fishes have no scales although the

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 epithelia ...

canal is well-developed and is situated high on the body parallel and near the base of the dorsal fin. The extant species both have maximum

total length Fish measurement is the measuring of individual fish and various parts of their anatomies, for data used in many areas of ichthyology, including taxonomy and fishery biology. Overall length Standard length (SL) is the length of a fish measured f ...

s of around .

Distribution and habitat

Trichodontid sandfishes are found in the North Pacific Ocean from Japan to California where they are found from the

intertidal zone The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...

down to depths of , although they are typically found in less than . They prefer soft substrates with a flat topography.

Biology

Trichodontid sandfishes are mainly

nocturnal Nocturnality is a ethology, behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite. Nocturnal creatur ...

and are attracted to lights on the surface. During the day they rest partially buried in the substrate with only the highest parts of the fish visible. They feed on small

invertebrates Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordate subphylum ...

References

* * {{Taxonbar, from=Q134421 Marine fish families Perciformes families