Beardfish

Beardfishes Temporal range: Late Cenomanian to present PreꞒ Ꞓ O S D C P T J K Pg N Possible Albian occurrence
Stout Beardfish, (P. nobilis)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
(unranked):	Acanthomorpha
Order:	Polymixiiformes Rosen & Patterson, 1969
Family:	Polymixiidae Bleeker, 1859
Type species
Polymixia nobilis R. T. Lowe, 1838
Families
†Boreiohydriidae Murray & Cumbaa 2013 †Dalmatichthyidae Radovčić 1975 †Digoriidae Bannikov 1985 †Dinopterygidae Jordan, 1923 Polymixiidae Gill 1862 †Pycnosteroididae Patterson, 1964
Synonyms
Polymixioidei Bleeker 1859

The beardfishes consist of a single extant genus, Polymixia, of deep-sea marine ray-finned fish named for their pair of long hyoid barbels. They are classified in their own order Polymixiiformes /pɒliˈmɪksi.ɪfɔːrmiːz/.^[1] But as Nelson says, "few groups have been shifted back and forth as frequently as this one, and they were recently added to Paracanthoptergii".^[2] For instance, they have previously been classified as belonging to the Beryciformes, and are presently considered either paracanthopterygians or the sister group to acanthopterygians. They are of little economic importance.^[3]

They are found in tropical and subtropical waters of the Atlantic, Indian and western Pacific Ocean. They are bottom-dwelling fish, found down to about 800 m (2,600 ft) depth. Most are relatively small fish, although one species, Polymixia berndti, is over 40 cm (16 in) in length.^[3]

The earliest body fossils are from the Late Cenomanian of Lebanon, of the genus Pycnosteroides.^[4] However, tentative earlier records are known from distinctive fossil otoliths from the Early Cretaceous (Albian) of Texas, USA.^[5] Many different fossil families and genera are known from the Late Cretaceous and early Cenozoic, in contrast to the relatively few surviving species in a single genus.^[6] Extant beardfish can thus be considered "living fossils".^[7]