The manta ray (Manta birostris) is the largest species of the rays. The largest known specimen was more than 7.6 metres (25 ft) across, with a weight of about 2,300 kilograms (5,100 lb). It ranges throughout tropical waters of the world, typically around coral reefs. They have the largest brain-to-body ratio of the sharks, rays and skates (Elasmobranchii).
Mantas have a variety of common names, including Atlantic manta, Pacific manta, devilfish, and just manta. At one time it was thought that there were many species of manta. However, the modern scientific consensus has been that there is just one species, a view supported by mitochondrial DNA studies.
Recent studies have suggested that manta rays actually comprise at least two different species, the giant manta (Manta birostris), which migrates, and another smaller one called the reef manta (Manta alfredi), which does not. The use of the "alfredi" name is questionable. The species alfredi was first used in the description of Prince Alfred's manta ray by Krefft in 1868.  Modern genetic studies have shown that Ceratoptera alfredi (Krefft, 1868), revised as Manta alfredi (Krefft, 1868), is a synonym of Manta birostris (Donndorff, 1798). The genus is generally considered to be in need of worldwide revision. Even the accepted name Manta birostris is often incorrectly ascribed to Walbaum (1792).
Evolution and taxonomy
Manta rays may have evolved from bottom-feeders, and then adapted to become open ocean filter feeders. This feeding strategy allowed them to grow larger than other ray species. Some ancestral characteristics degenerated due to the feeding change. For example, all that remains of the oral teeth is a small band of vestigial teeth on the lower jaw, almost hidden by the skin. The number and size of their dermal denticles are also reduced. Manta rays have a much thicker mucus body coating than other rays. Their spiracles have become small and non-functional, as all water is consumed orally. Mantas have a tail similar to stingrays, but they have lost their stinger and are harmless to divers.
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