Zoarcoidei

Zoarcoidei is a suborder of marine ray-finned fishes belonging to the order Perciformes. The suborder includes the wolffishes, gunnels and eelpouts. The suborder includes about 400 species. These fishes are predominantly found in the boreal seas of the Northern Hemisphere but they have colonised the Southern Hemisphere. Many members of this suborder are extremophiles adapted to deepwater ecosystems (including hydrothermal vents) and polar waters.^[1]

Zoarcoidei Temporal range: Middle Miocene to present PreꞒ Ꞓ O S D C P T J K Pg N
Atlantic wolffish Anarhichas lupus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Suborder:	Zoarcoidei
Families
see text

Taxonomy

Zoarcoidei was first proposed as a taxonomic grouping by the American zoologist Theodore Gill in 1893 as the superfamily Zoarceoidea.^[2] The 5th edition of Fishes of the World classifies the Zoarcoidei as a suborder within the order Scorpaeniformes.^[3] Other authorities classify this taxon as the infraorder Zoarcales within the suborder Cottoidei of the Perciformes because removing the Scorpaeniformes from the Perciformes renders that taxon non monophyletic.^[4] The monophyly of this grouping has still not been fully ascertained but it is generally accepted that the most basal family is Bathymasteridae.^[3]

Phylogenetic evidence suggests that despite their evolutionary, ecological & physiological diversity, zoarcoids have a relatively recent origin; although the stem group diverged from the Gasterosteoidei around the Early Eocene, the crown group only originated around the latest Oligocene, with most of the family-level divergences taking place over the Neogene. The acquirement of the type III antifreeze protein, which allowed for the group to thrive in freezing environments, appears to have occurred prior to the origin of the crown group, potentially during the Early Oligocene. The radiation into extreme habitats appears to have independently occurred in multiple lineages as a consequence of physiological changes and founder events.^[1] The earliest fossil remains of the group are from the mid-late Miocene (late Serravalian or early Tortonian) aged Agnevo Formation of Sakhalin, Russia.^[5]

Timeline

Superfamilies and Families

Zoarcoidei has the following superfamilies and families classified under it:^[3][6]

• Superfamily:Anarhichadoidea
  • Family:Anarhichadidae Bonaparte, 1835 (wolffishes)
  • Family:Cryptacanthodidae Gill, 1861 (wrymouths)
  • Family:Pholidae Gill, 1893 (gunnels)
  • Family:Stichaeidae Gill, 1864 (pricklebacks)
• Superfamily:Bathymasteroidea
  • Family:Ptilichthyidae Jordan & Gilbert, 1883 (Quillfish)
  • Family:Bathymasteridae Jordan & Gilbert, 1883 (ronquils)
• Superfamily:Zaproroidea
  • Family:Scytalinidae Jordan & Starks, 1895 (graveldiver)
  • Family:Zaproridae Jordan, 1896 (prowfish)
• Superfamily:Zoarcoidea
  • Family:Eulophiidae H. M. Smith, 1902 (Spinous eelpouts)^[7]
  • Family:Zoarcidae Swainson, 1839 (eelpouts)

Etymology

Zoarcoidei is based on the genus name Zoarces which was coined by Georges Cuvier in 1829 and which means "live bearing", as in the type species Zoarces viviparus, the viviparous blenny.^[8]

Characteristics

The Zoarcoidei families all share a single feature, the possession of a single nostril, and there is no other features or group of features which mark out the Zoarcoids as a taxonomic grouping.^[3] Some fish, like the ones in Stichaeidae and Anarhichadidae, resemble eels by using an Anguilliform body.

Distribution

The Zoarcoidei is thought to have originated in the northern hemisphere, particularly the northwestern Pacific Ocean and one of the families, the Zoarcidae, has colonised the southern hemisphere on a number of occasions.^[9]