Meet the Stenopterygius - the name is derived from stenos, Greek for "narrow", and pteryx, Greek for "fin" or "wing"

Stenopterygius quadriscissus is an ichthyosaur, an extinct animal whose body shape closely resembled that of today's fast-swimming fishes such as the tuna.

Stenopterygius was physically similar to the better known Ichthyosaurus, but had a smaller skull and narrower flippers.
Its skull was extended into a kind of a beak and was armed with a quantity of large teeth. The limbs had been transformed to fin-like structures. The tail terminated in a large, semicircular, leathery, vertical caudal fin and even a triangular dorsal fin was present.