Opistophthalmus tumas, Byg, 2023

Byg, Eric Ythier, 2023, A new species of Opistophthalmus C. L. Koch, 1837 from Namibia (Scorpiones: Scorpionidae), Faunitaxys 11 (23), pp. 1-6 : 1-4

Opistophthalmus tumas sp. n.

( Fig. 1-11, Tab. I)

ZooBank:http://zoobank.org/ BCA20FBB-56CF-4E04-8FDE-8E9B67D9444B

Holotype, ♂, Namibia, Erongo region, Namib-Naukluft National Park , Tumas Mount (Tumasberg) , J.-B. Lacroix leg. (No. 221), 1993, EY0288 ( EYPC), deposited in the MNHN.

Paratype, 1 ♀, same as holotype, deposited in the EYCP .

Reviewer:

Wilson Lourenço (Muséum national d’Histoire naturelle, ISYEB, UMR 7205- CNRS, Paris, France)

Etymology. – The specific name is placed in apposition to the generic name and refers to the inselberg of Tumas (“Tumasberg”) located in the Tumas plain ( “Tumas Vlakte ”), where the new species occurs.

Diagnosis. – Scorpion of small size for the genus, with a total length of 41 mm for the male holotype and 48 mm for the female paratype. Coloration basically brownish yellow. Carapace with anterior and median ocular furrows without suture; median ocular tubercle in antero-medial position, with carapace length over anterior distance of median eyes ratio of 2.28 in male, 2.05 in female. Genital operculum suboval, convex anteriorly and flat posteriorly in male, the opposite in female. Pectines strongly reduced; pectinal plate not divided; pectinal fully developed tooth count 3- 3 in male, 1- 1 in female. Metasoma with segments I to III without well-defined carinae and IV with dorsal and ventro-lateral carinae present and granular in male; female with segments I to IV without well-defined carinae; segment V with ventro-lateral carinae present and granular and dorso-lateral carinae absent in both sexes; segment V with dorsal surface smooth and lateral profile of ventral surface shallowly concave. Pedipalp chela manus with dorsal carinae strongly marked, composed of spiniform granules slightly larger than those of the dorso-lateral surface; manus moderately deep, with manus depth over carapace length ratio of 0.60 in male and 0.51 in female. Trichobothriotaxy of type C, neobothriotaxic; femur with 3 trichobothria, patella with 6-8 ventral and 22-23 external trichobothria, chela with 12-15 ventral, 2 internal, 6 dorsal and 14 external trichobothria. Legs I-II slightly compressed compared to III-IV, with anterior and posterior edges bearing a single row of long setae; tarsi with a longitudinal row of two (legs III) to three spines (legs III-IV) on the inner inferior surface; lateral lobes feebly developed with four internal and three external spines arranged in series, moderately developed; claws long, slender and almost straight.

Description (based on male holotype and female paratype; measurements in Table I).

Coloration. – Prosoma: carapace brownish yellow, turning to yellowish towards the anterior margin; median and lateral ocular tubercles marked with dark pigments. Mesosoma: tergites brownish yellow with confluent yellowish spots on the middle of tergites, forming a longitudinal stripe. Sternites yellowish. Coxapophysis and sternum yellowish; genital operculum and pectines pale yellow in male, yellowish in female. Metasoma: brownish yellow. Telson yellowish; aculeus pale yellow (male) to yellowish (female) at its base, reddish at its extremity. Chelicerae yellowish; fingers yellowish with reddish teeth. Pedipalps: femur and patella brownish yellow; chela brownish yellow with fingers yellowish in male, reddish in female; dentate margins of fingers reddish. Legs yellowish.

Morphology. Carapace acarinate, covered with minute granulation except around the median ocular tubercle in male, shiny and without any granulation in female; anterior and median ocular furrows without suture; anterior margin with a shallow concavity; posterior margin moderately (male) to feebly rounded (female); median ocular tubercle in antero-medial position, with carapace length over anterior distance of median eyes ratio of 2.28 in male, 2.05 in female; median eyes separated by about 1.3 (male) to 1.6 (female) ocular diameters; three pairs of lateral eyes, the first one smaller than the two others. Mesosoma: tergites acarinate; I to VI almost smooth in anterior one third and remaining two thirds covered with minute granules in male, entirely smooth and shiny in female; tergite VII entirely covered with minute granules in males, larger laterally, smooth in female with only few sparce granules laterally. Sternum pentagonal, slightly higher than wide. Venter:genital operculum suboval, formedby twoplateshaving a semitriangular shape; convex anteriorly and flat posteriorly in male, the opposite in female. Pectines strongly reduced in both sexes; pectinal plate not divided; pectinal fully developed tooth count 3- 3 in male, 1- 1 in female; sensory areas of pectinal teeth clearly outlined in male, strongly reduced to absent in female. Sternites almost entirely covered with granules in male, larger on V; female with sternites smooth and shiny, with only few sparce granules posteriorly on VII; spiracles linear and conspicuous. Metasoma: male with segments I to III without well-defined carinae, IV with dorsal and ventro-lateral carinae present and granular; female with segments I to IV without well-defined carinae; segment V with ventro-lateral carinae present and granular and dorso-lateral carinae absent in both sexes; intercarinal surfaces moderately to strongly granular ventrally and laterally in male, female with segments I to III smooth, IV-V moderately granular; dorsal surface of segments I to IV granulated posteriorly in male and smooth in female, segment V smooth in both sexes; lateral profile of ventral surface of segment V shallowly concave. Telson globular, with minute granules ventrally as its base; aculeus shorter than vesicle and moderately curved. Cheliceral dentition characteristic of the Scorpionidae (Vachon, 1963) . Pedipalps: femur with three incomplete carinae composed of a few granules, intercarinal surfaces with few sparce granules dorsally and anteriorly, other faces smooth; patella with two incomplete carinae composed of few granules, intercarinal surfaces with few sparce granules posteriorly and anteriorly, other faces smooth; chela manus with well-marked ventral carinae, granular; dorsal carinae strongly marked, composed of spiniform granules slightly larger than those of the dorso-lateral surface; dorso-external aspect of the manus coarsely granular, ventro-internal aspect smooth except few sparse granules internally in male; chela manus moderately deep in both sexes, with manus depth over carapace length ratio of 0.60 in male, 0.51 in female; dentate margin on fixed and movable fingers with five series of granules divided by larger accessory granules; a very large granule at the proximal end of the first series of granules on movable finger. Trichobothriotaxy of type C, neobothriotaxic (Vachon, 1974); femur with 3 trichobothria, patella with 6-8 ventral and 22-23 external trichobothria, chela with 12-15 ventral, 2 internal, 6 dorsal and 14 external trichobothria. Legs I-II slightly compressed compared to III-IV, with anterior and posterior edges bearing a single row of long setae; legs III-IV with few sparse setae except on anterior and posterior edges; tarsi with a longitudinal row of two (legs I-II) to three spines (legs III-IV) on the inner inferior surface; lateral lobes feebly developed with four internal and three external spines arranged in series, moderately developed; claws long, slender and almost straight.

Comparisons. – Opistophthalmus tumas sp. n. shows unquestionable similarities with its sister species O. holmi ( Lawrence, 1969) and O. jenseni ( Lamoral, 1972) in respect to several characters.

O. tumas sp. n. can however be easily distinguished from O. holmi ( Fig. 12-13) notably by the following main features:

(i) male metasoma with segment III with dorsal carinae absent to obsolete (present and distinct in O. holmi ) and segment IV with ventro-lateral carinae present and granular (absent to obsolete in O. holmi );

(ii) male metasoma with dorsal surface of segment V smooth, without granulation (granulated anteriorly in O. holmi ) and lateral profile of ventral surface shallowly concave (convex in O. holmi );

(iii) legs I-II slightly compressed (strongly compressed in O.holmi ), legs III-IV tarsi with a longitudinal row of three spines on the inner inferior surface (long setae in O. holmi ), lateral lobes of all legs with internal and external spines less developed than in O. holmi and claws shorter than in O. holmi ;

(iv) reduced trichobothriotaxy with patella with 6-8 ventral trichobothria (11-13 in O. holmi ) and 22-23 external trichobothria (26-30 in O. holmi ), chela with 12-15 ventral trichobothria (16-18 in O. holmi );

(v) moreover, both species occupy totally different biotopes, the new species occurring in the granite inselberg of Tumasberg (1000-1200 m altitude) while the ultra-psammophilous species O. holmi is distributed in the Namib desert dune system.

1 cm 3 4

O. tumas sp. n. can also be easily distinguished from O. jenseni notably by the following main features:

(i) median ocular tubercle in antero-medial position, with carapace length over anterior distance of median eyes ratio of 2.28 in male (2.10-2.15 in O. jenseni );

(ii) male metasoma with dorsal surface of segment V smooth, without granulation (granulated anteriorly in O. jenseni );

(iii) pedipalp chela manus with dorsal carinae composed of spiniform granules slightly larger than those of the dorso-lateral surface (much larger and longer in O. jenseni ); manus moderately deep, with manus depth over carapace length ratio of 0.60 in male (distinctly deep in O. jenseni with a ratio of 0.70);

(iv) legs III-IV tarsi with a longitudinal row of three spines on the inner inferior surface (two spines in O. jenseni );

(v) reduced trichobothriotaxy with patella with 6-8 ventral trichobothria (9-10 in O. jenseni ) and 22-23 external trichobothria (30-31 in O. jenseni ; as in Lamoral, 1979), chela with 12-15 ventral trichobothria (18-20 in O. jenseni ), chela fixed finger trichobothrium est at similar distance from esb and et (closer to et in O. jenseni ).