flounders are flat bodyed fish. would they adapted to live in rhe headwaters of a river

A clade within this diverse family, the Neoselachii, emerged by the Triassic, with the best-understood neoselachian fossils dating from the Jurassic.

Fossil denticles (tooth-like scales in the skin) resembling those of today's chondrichthyans date at least as far back as the Ordovician, with the oldest unambiguous fossils of cartilaginous fish dating from the middle Devonian.

Skates belong to the ancient lineage of cartilaginous fishes. Members of Rajidae are distinguished by a stiff snout and a rostrum that is not reduced.

Alternatively, the name 'skate' is used to refer to the entire order of Rajiformes (families Anacanthobatidae, Arhynchobatidae, Gurgesiellidae and Rajidae). Softnose skates and pygmy skates were previously treated as subfamilies of Rajidae (Arhynchobatinae and Gurgesiellinae), but are now considered as distinct families. More than 150 species have been described, in 17 genera. Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays.

Flounders are flat bodyed fish. would they adapted to live in rhe headwaters of a river