Sunday, November 06, 2016

Yucatán Manta Ray?



See those Mantas?
They sure look different - and I cite.
Manta sp. cf. birostris

Selected synonymy. Cephalopterus giorna Lesueur, 1824.
Common names. Atlantic manta ray, Caribbean manta ray

Diagnosis. Overall body shape and size similar to M. birostris, although differences in colouration, denticles and dentition occur. Maximum disc width over 6000 mm. Slender whip-like tail with reduced caudal spine predominantly encased in a calcified mass present on the dorsum of tail immediately posterior to the dorsal fin. Small, knob-like dermal denticles occur on both the dorsal and ventral surfaces, which are non- overlapping but densely and non-uniformly distributed. Ventral surface has slightly larger denticles. Terminal mouth with tooth band on lower jaw comprising 77% of total jaw width and containing 9–11 rows of small cusped teeth.
A third, putative species, Manta sp . cf. birostris, in the Atlantic may be distinct from M. birostris.
This putative species shares some characteristics with M. birostris, such as a large maximum disc width and the presence of a distinct, reduced caudal spine. However, from the limited specimens and photographs examined, clear differences exist between Manta sp. cf. birostris and M. birostris including dissimilar denticle morphology and distribution, intermediary dentition and, most noticeably, differences in dorsal and ventral colouration.
While Manta sp. cf. birostris occurs in sympatry with M. birostris in parts of the Atlantic and Caribbean, there is some evidence that differences in fine-scale habitat selection and seasonal habitat use may occur in some locations (Bigelow and Schroeder 1953, Notarbartolo-di-Sciara and Hillyer 1989). Bigelow and Schroeder’s (1953) description of M. birostris from the Western Atlantic is one of the most comprehensive descriptions compiled, but includes material from both the wide-ranging M. birostris and the localized Manta sp. cf. birostris. To help clarify the situation, photographs, notations on colouration and descriptions of denticle and tooth morphology of both M. birostris and Manta sp. cf. birostris have been provided to supplement this description.

At present there is not enough empirical evidence to warrant the separation of a third species of Manta.
At minimum, additional examination of dead specimens of Manta sp. cf. birostris are necessary to clarify the taxonomic status of this variant manta ray. Further examinations of the distribution of Manta sp. cf. birostris, as well as, studies of its ecology and behaviour within the Atlantic and Caribbean are also recommended.

If distinct, we propose that a third species of Manta , Manta giorna, be resurrected from Lesueur’s (1824) description from North America.
That was back then in 2008 when Andrea resurrected the Reef Manta.
And after that, alas, having become the Queen of Mantas, Andrea's career appears to have become, for lack of a better description, a tad less focused and the third Manta Ray is still awaiting description.

Anyway, voids tend to get filled, and others have now stepped in.
I must say that despite of very much being a lumper, I really like this paper, that the evidence looks compelling and that I'm totally sold on the idea of a third species - but who am I to say, the more as naming the Yucatán Manta Ray cannot yet be performed without careful inspection and genetic analyses of several museum specimens.

Any takers?
Or will we have to wait for another 8 years for the final solution to this fascinating riddle?

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