Physoctonus amazonicus, Lourenco, Wilson R., 2017

Lourenco, Wilson R., 2017, A new species of Physoctonus Mello-Leitao, 1934 from the ' Campos formations' of southern Amazonia (Scorpiones, Buthidae), ZooKeys 711, pp. 67-80 : 72-76

Physoctonus amazonicus sp. n. Figs 4, 5, 6

Diagnosis.

Medium to small sized scorpion, measuring 28.4 mm in total length for female. General colouration yellow with a brownish inverted triangle covering the anterior margin of carapace; well-marked brownish spots over the lateral edges of carapace and tergites; tergites with a median longitudinal spot which becomes confluent on III to VI; ventral aspect of metasomal segments and appendages intensely spotted. Median ocular tubercle anterior to the centre of carapace; three pairs of lateral eyes. Chelicerae with dentition following the buthid pattern; movable fingers with two small basal teeth, not fused ( Vachon 1963). Pedipalps fixed and movable fingers with 7-8 linear rows of granules, and inconspicuous internal and external accessory granules. Sternum between subtriangular and subpentagonal. Pectines small with 13-14 teeth; no stridulatory apparatus; fulcra moderately marked; basal middle lamellae not dilated in female; basal piece strongly marked. Sternites with short linear spiracles. Telson with a globular vesicle; aculeus long and strongly curved, with a vestigial spinoid subaculear tooth. Trichobothrial pattern of type A-α (alpha) - orthobothriotaxic ( Vachon 1974, 1975) Tibial spurs absent; pedal spurs reduced.

Type material.

Brazil, State of Pará, Campos do Pará, region between rivers Xingu and Araguaya, under termite mound (Fig. 7), XII/1929 (J. Vellard). One female holotype deposited in the collections of the Muséum national d’Histoire naturelle, Paris.

Etymology.

The specific name refers to Amazonia, region where the new species was found.

Relationships.

The new species seems to be closer related to Physoctonus debilis (C. L. Koch, 1840). Both species can, however, be distinguished by a number of features: (i) a darker general colouration with pigmentation and spots more clearly marked on legs, pedipalps, lateral edges of carapace, tergites, and ventral aspect of metasoma (Figs 4-8), (ii) a more flattened body with a larger mesosoma, (iii) a more strongly marked basal piece, (iv) telson aculeus more strongly curved, (v) trichobothrium db of fixed finger only slightly basal to et. Moreover, the two species are found in different habitats and are geographically isolated (see ecological and biogeographical comments).

Description.

Based on female holotype. Measurements after the description.

Colouration. Basically yellow strongly marked with brownish spots. Prosoma: carapace yellow with a brownish inverted triangle covering the anterior margin of carapace and well-marked brownish spots over the lateral edges; eyes surrounded with black pigment. Mesosoma: tergites yellow with a median longitudinal spot which becomes confluent on III to VI; lateral edges equally spot as for carapace. Metasomal segments I to IV yellow; V reddish-yellow to reddish-brown; segments II to V strongly infuscate ventrally; carinae dark. Vesicle of same colour as segment V; aculeus yellow at the base and reddish on tip. Venter yellow; genital operculum and pectines pale yellow. Chelicerae yellow with a brownish thread; fingers yellow with reddish teeth. Pedipalps yellow with intense but diffused brownish spots; carinae and granulations on the edge of fingers reddish. Legs yellow with intense diffused brownish spots.

Morphology. Carapace strongly granular but with a thin granulation; anterior margin with a median concavity. Anterior median and posterior median carinae moderate to weak. All furrows moderately to weakly deep. Median ocular tubercle distinctly anterior to the centre of the carapace. Eyes separated by approximately one ocular diameter. Three pairs of lateral eyes. Sternum subtriangular to subpentagonal. Mesosoma flattened and enlarged; tergites moderately to strongly granular. Median carina moderate to strong in all tergites. Tergite VII pentacarinate. Venter: genital operculum divided longitudinally, forming two oval plates; basal piece strongly marked. Pectines with 13-14 teeth. Sternites smooth with short linear spiracles; sternite III with some punctations; sternite VII with four carinae and minute granulations. Metasomal segments I to III with ten carinae; IV with eight carinae; V with five carinae; intermediate carinae totally incomplete on segment III. Intercarinal spaces weakly granular on segments I to IV; more clearly marked on V. Telson roughly granular with a long and strongly curved aculeus, slightly shorter than vesicle. Subaculear tooth vestigial. Cheliceral dentition characteristic of the family Buthidae ; basal teeth on movable finger reduced but not fused; ventral aspect of both fingers and manus with dense, long setae ( Vachon 1963). Pedipalps: femur pentacarinate; patella with seven carinae; chela with nine carinae, weakly marked; internal aspects of femur and patella with several spinoid granules; all faces weakly granular. Fixed and movable fingers with 7-8 linear rows of granules and weakly marked internal and external accessory granules. Trichobothriotaxy: orthobothriotaxy A- (alpha) ( Vachon 1974, 1975). Legs: tarsus ventrally with numerous short fine setae; pedal spurs moderate; tibial spurs absent.

Comparative morphometric values (in mm) of an adult female of Physoctonus debilis from Caxias Maranhão state and the female holotype of Physoctonus amazonicus sp. n. Total length, 28.3/28.4 (including telson). Carapace: length, 3.7/3.6; anterior width, 2.3/2.4; posterior width, 3.9/4.4. Mesosoma length, 8.6/8.2. Metasomal seg ments. I: length, 2.0/2.1; width, 2.2/2.1; II: length, 2.3/2.5; width, 1.9/2.0; III: length, 2.6/2.7; width, 2.1/2.0; IV: length, 3.0/3.1; width, 2.2/2.2; V: length, 3.1/3.4; width, 2.2/2.2; depth, 1.6/1.4. Telson: length, 3.0/2.8; width, 1.2/1.3; depth, 1.2/1.2. Pedipalp: femur length, 3.5/3.4, width, 1.2/1.1; patella length, 3.9/3.7, width, 1.6/1.5; chela length, 6.8/6.7, width, 1.3/1.5, depth, 1.0/1.2; movable finger length, 4.6/4.5.