''Eschmeyer nexus'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of marine

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 ...

; it is the only species in the

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 ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

''Eschmeyer'' and monogeneric

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 ...

Eschmeyeridae. This fish is only known from the

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

, near

Fiji Fiji, officially the Republic of Fiji, is an island country in Melanesia, part of Oceania in the South Pacific Ocean. It lies about north-northeast of New Zealand. Fiji consists of an archipelago of more than 330 islands—of which about ...

Taxonomy

''Eschmeyer nexus'' was first formally described in 1983 by the American

ichthyologists 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 ...

Stuart G. Poss and

Victor G. Springer Victor Gruschka Springer (June 2, 1928 – September 18, 2022) was an American biologist who was a Senior Scientist emeritus, Division of Fishes at the Smithsonian Institution's National Museum of Natural History. He was a specialist in the a ...

with the type locality given as Fiji. Poss and Springer placed their new species in the new monotypic genus ''Eschmeyer'' and in 2001

Sergey Anatolyevich Mandritsa Sergey may refer to: * Sergey (name), a Russian given name (including a list of people with the name) * Sergey, Switzerland Sergey is a municipality in the district of Jura-Nord Vaudois in the canton of Vaud in Switzerland. History Sergey is f ...

classified that genus within the monogeneric family Eschmeyeridae, The 5th 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 ...

'' classifies the family within 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 ...

Scorpaenoidei Scorpaenoidei is a suborder of Actinopterygii, ray-finned fishes, part of the Order (biology), order Perciformes, that includes the scorpionfishes, lionfishes and velvetfishes. This suborder is at its most diverse in the Pacific and Indian Oceans ...

which in turn is classified within 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 ...

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 authorities place the Scorpaenoidei within the

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 ...

. A recent study placed the genus ''Eschmeyer'' into an expanded stonefish clade, the Synanceiidae, because all of these fish have a lachrymal sabre that can project a switch-blade-like mechanism out from underneath their eye. The name of both the genus and family honours

William N. Eschmeyer William Neil Eschmeyer (February 11, 1939 – December 30, 2024) was an American ichthyologist. He was the founder and developer of the database and reference work Catalog of Fishes, hosted by the California Academy of Sciences and available both o ...

, an American ichthyologist at the California Academy of Sciences, or his work on the Scorpaenid fishes. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

''nexus'', is derived from , Latin for 'tie' or 'connect', a reference to the suite of features suggesting this taxon has a close relationship with a number of groups within the Scorpaenoidei. Mandritsa suggested the English common name of ''cofish'' in recognition of Eschmeyer’s participation in the ''

Catalog of Fishes Catalog of Fishes is a comprehensive on-line database and reference work on the scientific names of fish species and genera. It is global in its scope and is hosted by the California Academy of Sciences. It has been compiled and is continuously up ...

''.

Description

''Eschmeyer nexus'' has eight spines and thirteen soft rays in the

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 ...

, with the first few dorsal fin spines being very short, while 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 ...

has three spines and eight soft rays. All the fin rays are unbranched. The front part of the throat, the isthmus, does not have any fleshy papillae and the gill membranes do not have a wide junction with the isthmus. The frontal and parietal bones are well developed. There are no spines on the preorbital bone. The only scales are those on 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 ...

which has ten tubed scales. There are no spiny projections to the rear of the

caudal peduncle 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 only ...

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 ...

membrane is joined to the body and is fused to the membrane of opposite pelvic fin. There is no detached

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

ray. This is a small fish with a maximum

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

of .

Distribution and habitat

''Eschmeyer nexus'' is found in the western central Pacific Ocean where it has only been recorded from Fiji. It is a

demersal fish Demersal fish, also known as groundfish, live and feed on or near the bottom of seas or lakes (the demersal zone).Walrond Carl . "Coastal fish - Fish of the open sea floor"Te Ara - the Encyclopedia of New Zealand. Updated 2 March 2009 They oc ...

References

{{Taxonbar, from2=Q2681788, from1=Q289456, from3=Q1926873 Scorpaenoidei Taxa named by Victor G. Springer Taxa named by Stuart G. Poss Fish described in 1983