New species are described with some regularity and undescribed species likely remain. In particular, Tephrinectes sinensis may represent a family-level lineage and requires further evaluation e.g. The taxonomy of some groups is in need of a review, as the last monograph covering the entire order was John Roxborough Norman's Monograph of the Flatfishes published in 1934. The Paralichthyidae has long been indicated to be paraphyletic, with the formal description of Cyclopsettidae in 2019 resulting in the split of this family as well. The families Paralichthodidae, Poecilopsettidae, and Rhombosoleidae were also traditionally treated as subfamilies of Pleuronectidae, but are now recognised as families in their own right. For example, the Achiridae were classified as a subfamily of Soleidae in the past, and the Samaridae were considered a subfamily of the Pleuronectidae.

Some families are the results of relatively recent splits. There also exist two monotypic families ( Paralichthodidae and Oncopteridae). The largest families are Soleidae, Bothidae and Cynoglossidae with more than 150 species each. Broadly, the flatfishes are divided into two suborders, Psettodoidei and Pleuronectoidei, with > 99% of the species diversity found within the Pleuronectoidei. Over 800 described species are placed into 16 families. Some flatfish can camouflage themselves on the ocean floor. Many important food fish are in this order, including the flounders, soles, turbot, plaice, and halibut. Some species face their left sides upward, some face their right sides upward, and others face either side upward. In many species, both eyes lie on one side of the head, one or the other migrating through or around the head during development. Paralichthodidae (measles flounders) Poecilopsettidae (bigeye flounders) Rhombosoleidae (rhombosoleids) Achiropsettidae (southern flounders) Samaridae (crested flounders) Achiridae (American soles) Soleidae (true soles) Cynoglossidae (tonguefishes)Ī flatfish is a member of the ray-finned demersal fish order Pleuronectiformes, also called the Heterosomata, sometimes classified as a suborder of Perciformes.

Scophthalmidae (turbots) Paralichthyidae (large-tooth flounders) Pleuronectidae (righteye flounders) Bothidae (lefteye flounders) Superfamily Soleoidea Suborder Pleuronectoidei Superfamily CitharoideaĬitharidae (largescale flounders) Superfamily Pleuronectoidea Suborder Psettodoidei Psettodidae (spiny turbots)

Giant flat fish