Rhopalurus pintoi, Mello-Leitao, 1932

Teruel, Rolando & Tietz, Alexander K., 2008, The true identity of Rhopalurus pintoi Mello-Leitão, 1932, with notes on the status and distribution of Rhopalurus crassicauda Caporiacco, 1947 (Scorpiones: Buthidae), Euscorpius 70 (70), pp. 1-14 : 6-8

Comparisons: R. pintoi is very unique and easy to recognize on the basis of several important features: (a) coloration entirely blackish; (b) pedipalp fingers with

9–10 principal rows of granules; (c) female with a very large and deep discal pit basal on the pectinal plate; (d) males and females with pectinal tooth counts not overlapping. All other species of Rhopalurus possess fingers with eight rows of granules, basal pectinal plate without a discal pit and pectinal tooth counts which are very similar in both sexes or at least conspicuously overlapping; furthermore, the single species with an entirely blackish morph is the Cuban endemic Rhopalurus junceus (Herbst, 1800) , but this scorpion has much lower pectinal tooth counts (male 17–22, female 15–21), pedipalps much more robust and with very strong lobe/notch combination, and metasomal segments II–IV with only eight carinae.

MATERIAL EXAMINED: Guyana, Southwestern , Rupununi, March 2008, H.-W. Auer, 2 adult ♂♂, 1 adult ♀, 2 juvenile ♀♀ ( RTO: Sco.0383), 1 adult ♀, 3 juvenile ♂♂, 3 juvenile ♀♀ ( AKT) , 1 adult ♂ ( AMNH) .

Remarks: there is no doubt that the specimens herein studied belong to R. pintoi , as they posses two characters which are absolutely diagnostic for the taxon and were explicitly described by Mello-Leitão (1932) for the holotype: the presence of 9–10 rows of granules on pedipalp fingers and the entirely blackish coloration; all other species in the genus possess eight (exceptionally seven) row of granules, and no other South American taxa exhibit such dark coloration.

On the other hand, the confirmation that R. piceus is just a junior synonym of R. pintoi is not a surprise, as it had already been suggested by Teruel (2006: 51–52) based on the absolute match of the original descriptions and locality records of both taxa. When Mello-Leitão (1932) described R. pintoi , he made special emphasis on its distinctive blackish color because it was unprecedented for the genus. When Lourenço (1982) revised the genus, the holotype of R. pintoi was already lost and from the same general area (Roraima) he had available only specimens of R. crassicauda , which were correctly associated by him to R. laticauda (both species are indeed very close, see below), but as these specimens did not possess the dark color described originally by Mello-Leitão, Lourenço (1982) simply ignored such a conspicuous incongruence and regarded first R. crassicauda as a junior synonym of R. pintoi , and then the latter as a junior synonym of R. laticauda with subspecific rank as R. laticauda pintoi . Fifteen years latter, a black Rhopalurus was found in Roraima by Lourenço & Pinto-da-Rocha (1997), but strangely these authors not only avoided to make any mention to R. pintoi , but described this scorpion as a new species on the basis of the same characters originally used by Mello-Leitão (1932) to diagnose R. pintoi (the blackish coloration and the high number of granular rows on pedipalp fingers). Five years later, Lourenço himself appeared to take notice of the conflictive situation created on the identity on both taxa, but his approach to this problem was even more controversial: he regarded R. pintoi as a nomen nudum and retained R. piceus as valid, ambiguously stating that both species "... may eventually be found to be associated... " ( Lourenço, 2002: 304–305).

Very recently, Teruel (2006) demonstrated that the nomen nudum category applied by Lourenço (2002) was clearly erroneous according to the CINZ (2000), restored R. pintoi as a valid species, and suggested that R. piceus was very probably its junior synonym, but did not establish the formal synonymy due to lack of adequate material. Fortunately, new specimens are now available, and careful study of them confirmed that R. pintoi is a fully valid species and R. piceus represents its junior synonym, and thus the following synonymy is herein established: Rhopalurus pintoi Mello-Leitão, 1932 = Rhopalurus piceus Lourenço et Pinto-da-Rocha, 1997, new synonym.

It is noteworthy to mention that most of the nomenclatural confusion that has surrounded the status of R. pintoi and R. piceus has originated because in their original descriptions the sex and/or maturity of the types have been erroneously determined. The holotype of R. pintoi was declared as male by Mello-Leitão (1932), but its slender habitus and low pectinal tooth count of 20/21 (depicted as 21/ 21 in his figure 2a) clearly demonstrate that it was a female. Also, the holotype and one paratype of R. piceus sexed as males by Lourenço & Pinto-da-Rocha (1997) are in fact females, as reveal their low pectinal tooth counts (23/24 and 22/22, respectively) and the presence of a large discal pit in the basal pectinal plate (visible in their figure 18); furthermore, the four types of R. piceus supposed to be adults are undoubtedly juveniles, as evidence its very slender pedipalp chelae and slightly incrassate metasoma (i.e., compare their figures 17–18 to Figure 4 of the present paper).

Even though the holotype of R. pintoi is currently thought to be lost and the types of its junior synonym R. piceus are all juveniles, it is unnecessary to designate a neotype for R. pintoi because its main diagnostic characters (particularly the color pattern, number of rows of granules on pedipalp fingers and presence of a large discal pit on the female basal pectinal plate) are so unique inside the genus Rhopalurus that warrant an easy and accurate identification for this taxon.

Figures

Figure 4: Juvenile female Rhopalurus pintoi from Rupununi, still alive in captivity.