Melvius is a genus of vidalamiin amiid ray-finned fish from the Late Cretaceous.

[3] The type species, Melvius thomasi, was described by Bryant in 1987 from Hell Creek Formation.

[4] A second species Melvius chauliodous, was named and described by Hall and Wolburg in 1989 from Kirtland Formation,[5] and it is now considered to be one of the index taxa of the Kirtlandian land-vertebrate age.

A vertebral remain of M. thomasi would belongs to fish with standard length (length between tip of snout and the base of the caudal fin) of 161 cm (5.28 ft), and there are some specimens exceeds height of that vertebra.

[7] However, M. thomasi would be a “dwarf” compared to M. chauliodous, a specimen of M. chauliodous with abdominal centra which is 6.57 cm (2.59 in) wide would indicate standard length over 2 m (6.6 ft), and there is even larger abdominal centra which is 7.3 cm (2.9 in) wide.