Hippoglossus, Heteronectes, Amphistium, Psettodes and Cynoglossus

Heteronectes chaneti (Friedman 2008, 2012) is an Eocene fish with an assymetric face originally and here considered basal to extant flatfish. Note the presence of circumorbital bones.

Amphistium paradoxum (Agassiz 1835) is an Eocene fish with an asymmetric face, transitional to extant flatfish. It also has the flatfish shape, so it probably swam broadside down. U of Chicago News

Psettodes erumei (Bloch and Schneider 1801) is the extant Indian halibut. This genus is often considered the most basal extant flatfish, but note the lack of circumorbital bones. The lower eye has not rotated completely to the upper side. Here are fewer, but larger teeth. The lower jaws include a second row of large teeth medial to the lateral teeth.

Hippoglossus hippoglossus (Linneaus 1758; up to 4.7m in length) is the extant Atlantic halibut, one of the flounders, a fish that lives its life on its pale blind side. Two eyes appear on the dark and camouflaged upper side.

Cynoglossus puncticeps (Hamilton-Buchanan 1822) is the extant speckled tongue sole. Here the pectoral fins are abent, both eyes are ventral to the lateral line, the dorsal fin runs from the anterior of the snout around the tapered tail to the anus. The mouth is subterminal.

Agassiz L 1835. Recherches Sur Les Poissons Fossiles. Tome IV (livr. 4). Imprimerie de Petitpierre, Neuchatel 33-52.

Bloch ME and Schneider JG 1801. Systema Ichthyologiae Iconibus cx Ilustratum. Post obitum auctoris opus inchoatum absolvit, correxit, interpolavit Jo. Gottlob Schneider, Saxo. Berolini. Sumtibus Auctoris Impressum et Bibliopolio Sanderiano Commissum. i-lx + 1-584, Pls. 1-110.

Friedman M 2008. The evolutionary origin of flatfish asymmetry. Nature 454:209–212.

Friedman M 2012. Osteology of †Heteronectes chaneti (Acanthomorpha, Pleuronectiformes), an Eocene stem flatfish, with a discussion of flatfish sister-group relationships. Journal of Vertebrate Paleontology (32) 4: 735-756; doi: 10.1080/02724634.2012.661352

Hamilton-Buchanan F 1822. An Account of the Fishes Found in the River Ganges and Its Branches. 405 pages, 39 plates. Edinburgh: Archibald Constable

Harrington RC, et al. (6 co-authors) 2016. Phylogenomic analysis of carangimorph fishes reveals flatfish asymmetry arose in a blink of the evolutionary eye. BMC Evolutionary Biology 16 (224).

Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.

McCoy F 1855. A synopsis of the classification of the British Palaeozoic rocks, with a systematic description of the British Palaeozoic fossils. Fasciculus 3, Mollusca and Palaeozoic fishes. British Palaeozoic Fossils, Part II. Palaeontology 407-666.

Menon AGK 1977. A systematic monograph of the tongue soles of the gemus Cynoglossus Hamilton-Buchanan (Pisces: Cynoglossidae). Smithsonian Contributions to Zoology 238:1–129.

wiki/Spiny_turbot
wiki/Flatfish
wiki/Hippoglossus
wiki/Atlantic_threadfin
wiki/Heteronectes
wiki/Amphistium
wiki/Cynoglossus