Two other families, the butterfly rays (Gymnuridae) and cow-nosed rays (Rhinopteridae), are found in shallow coastal waters of tropical and warm temperate seas and reach widths of about 2 metres. The possible existence of another stingray family, consisting of deepwater species, was indicated in 1981 with the identification of Hexatrygon bickelli. The specimen, found on the coast of South Africa, showed unique adaptations to deepwater life and was classified by its discoverers in a separate family and suborder.