Gobioidei

The Gobioidei are a suborder of percomorph fish. Many of these fishes are called gobies. It is by far the largest and most diverse order within the order Gobiiformes, and one of the most diverse groups of ray-finned fish in general. The suborder, which was previously considered a suborder of Perciformes, is made up of about 2,211 species that are divided between seven families. Phylogenetic relationships of the Gobioidei have been elucidated using molecular data. Gobies are primarily small species, often with large heads and tapered bodies, that live in marine water, but roughly 10% of these species inhabit fresh water. This order is composed chiefly of benthic or burrowing species; like many other benthic fishes, most gobioids do not have a gas bladder or any other means of controlling their buoyancy in water, so they must spend most of their time on or near the bottom. Traditionally most of the species called gobies have been classified in the order Perciformes as the suborder Gobioidei but in the 5th Edition of Fishes of the World this suborder is elevated to an order Gobiiformes within the clade Percomorpha. In the most recent taxonomic treatment, they are again placed as the suborder Gobioidei within an expanded Gobiiformes.