Pholidae is a family of marine ray-finned fishes, known as gunnels, in the scorpaeniform suborder Zoarcoidei. These are fishes of the littoral zone and are mainly found in North Pacific Ocean, with two species found in the North Atlantic Ocean and Arctic Ocean. Taxonomy Pholidae was first put forward as a family in 1893 by the American zoologist Theodore Gill. The 5th edition of Fishes of the World classifies this family within the suborder Zoarcoidei, within the order Scorpaeniformes. Other authorities classify this family in the infraorder Zoarcales wihin the suborder Cottoidei of the Perciformes because removing the Scorpaeniformes from the Perciformes renders that taxon non monophyletic. Etymology and spelling Pholidae is derived from the name of the type genus Pholis which is an Ancient Greek name for a fish that hides in a hole, the name dating at least as far in history as Aristotle. The family has been spelled as Pholididae, and this is grammatically correct, but Article 29 of the International Code of Zoological Nomenclature permits the use of Pholidae. Subfamilies and genera The Pholidae is subdivided into two subfamilies, four genera with a total of 15 species: Subfamily Pholinae Gill, 1893 Genus Pholis Scopoli, 1777 Subfamily Apodichthyinae Hubbs, 1927 Genus Apodichthys Girard, 1854 Genus Rhodymenichthys Jordan & Evermann, 1896 Genus Ulvicola Gilbert & Starks, 1897 Characteristics Pholidae, the gunnels, have elongate, compressed bodies which resemble that of blennies. There is a single continuous dorsal fin, which has a base that is roughly double the length to that of the anal fin, the dorsal fin extends from the head to the caudal fin. The dorsal fin contains between 73 and 100 stiff spines while the anal fin has between 1 and 3 spines and 32 to 53 soft rays. the nala fin and the dorsal fin are joined to the rounded caudal fin. Some species have no pectoral fins but where they are present they are very small. The pelvic fins are also small, if present, and very simple with a single spine and a single soft ray. There is a single pair of nostrils. The body is covered with very small, difficult to see, cycloid scales which are covered in mucus. the sensory canals on the head have pores which are open to the outside. The lateral line runs along the middle of the flanks and is made up of a row of superficial neuromasts. The