Manta ray. Manta rays are large eagle rays belonging to the genus Manta. The larger species, M. birostris, reaches 7 m (23 ft) in width while the smaller, M. alfredi, reaches 5.5 m (18 ft). Both have triangular pectoral fins, horn-shaped cephalic fins and large, forward-facing mouths. They are classified among the Elasmobranchii (sharks and rays) and are placed in the eagle ray family Myliobatidae.