Flatfish entire order was John Roxborough Norman's "Monograph of the Flatfishes" published in 1934. New species are described with some regularity and undescribed species likely remain. Hybrids are well known in flatfishes. The Pleuronectidae, of marine fishes, have the largest number of reported hybrids. Two of the most famous intergeneric hybrids are between the European plaice ("Pleuronectes platessa") and European flounder ("Platichthys flesus") in the Baltic Sea, and between the English sole ("Parophrys vetulus") and starry flounder ("Platichthys stellatus") in Puget Sound. The offspring of the latter species pair is popularly known as the hybrid sole and was initially believed to
Platy (fish) they are olive in color with black marbling or spots on the side of the caudal peduncle. Large males show blackish blotches on the dorsal fin. Unlike some other members of the genus, "X. variatus" has no claw at the tip ]] ray. The fourth pectoral ray shows well-developed serrae (i.e. saw-like notches). They typically have 20 to 24 lateral scales, 10 to 12 dorsal rays and two rows of jaw teeth. Platy is widely used in tropical aquariums. Several different color variations have been developed, such as red, yellow, orange, blue, rainbow (combination of colors) and white. Platy (fish)