Taxonomy
At one time it was thought that there were many species of manta. In the last few decades, the scientific consensus had been that there was just one species, Manta birostris.
The early view that "black" and "white" mantas were different species was also discounted through a study of mitochondrial DNA in 2001, which however did reveal some general geographic patterns: Based on limited sampling, west Pacific mantas formed one clade, east Pacific and some Caribbean mantas formed a second clade, and finally the remaining Caribbean mantas formed a third clade.
A similar pattern emerged in a study in 2009 based on morphology, including color, dermal denticles and teeth: A smaller species, up to about 5.5 m (18 ft) in width, M. alfredi is found in the Indo-Pacific and tropical east Atlantic, and a larger, up to at least 7 m (23 ft) in width, M. birostris is found throughout tropical, subtropical and warm temperate oceans, but it has not yet been documented from most islands in the southwest Pacific. The former species appears to be more coastal, while the latter appears to be more pelagic and possibly migratory. Both these species occur in a normal, a black and a rare white morph, confirming the view that simply dividing into species based on morph (as had been done earlier) is incorrect. A third possible species in the genus, preliminarily referred to as Manta sp. cf. birostris, reaches at least 6 m (20 ft) in width, and is known from the tropical west Atlantic, including the Caribbean. M. birostris overlaps in distribution with Manta sp. cf. birostris, matching the presence of two Caribbean clades in earlier studies of mtDNA. Based on mantas found in oceans around Japan, a study in 2010 confirmed both the morphological and genetic differences between M. birostris and M. alfredi.
The use of the "alfredi" for the smaller species is questionable. The specific name alfredi was first used in Krefft's description of Prince Alfred's manta ray in 1868. Even the accepted name Manta birostris is often incorrectly ascribed to Walbaum (1792).
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