Taxonomy

Discovery and description

The first specimen of the threadfin dragonfish to be described was caught close to the shore in a net according to naturalist and reverend Richard Thomas Lowe (Lowe 1843). In his description, Lowe mentions the rows of dots along the sides of the fish.

These are the photophores used for producing light, but as the fish was dead when Lowe examined it, he had no means of deducing their function.

He states that the specimen was “uniform dark chocolate-brown”. As can be seen in the photograph of the holotype - this colour has now been completely lost.

Lowe also speculates that the fish might be related to moray eels which, although wrong, is understandable given its appearance.

Classification

Within the order Stomiiformes, Echiostoma barbatum was initially placed within the family Melanostomiidae - the ‘scaleless dragonfishes’.

After a revision of the order (Fink, 1985) this was downgraded to the subfamily Melanostominae within the family Stomiidae.

E.barbatum is easily distinguished from its closest relatives within the Melanostominae by its pectoral fins which each have 1 very long fin ray distinctly separated from 3 smaller rays, hence its common name, the threadfin dragonfish.

Other species and subspecies within the genus Echiostoma are:

  • Echiostoma calliobarba (Parr, 1934)
  • Echiostoma ctenobarba (Parr, 1927)
  • Echiostoma ctenobarba ramifer (Parr, 1934)
  • Echiostoma guentheri (Regan and Trewavas, 1930)

Researchers have since concluded that these, along with another species called Hyperchoristus tanneri, are all synonyms of Echiostoma barbatum - they are all based on specimens that are now regarded as Echiostoma barbatum.

Some of this confusion has arisen because of the variable structure of E.barbatum’s barbel.

Hyperchoristus tanneri was described by Theodore Nicholas Gill in 1883 based on a specimen caught by, and named after, a Captain Tanner. He writes, “a black fish with formidable teeth, which was so lively when brought to the surface that it twisted itself round in its attempt to bite the commander of the vessel, Captain Tanner”.

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Glossary
Holotype

If only one type specimen is mentioned in the original description, it is called a holotype.

Photophores

Light emitting organs that appear as luminous spots.

Type specimen

Type specimens are used to provide the first description of a species and serve as the definitive example of that species for comparative purposes.