Lychas chanthaburiensis, Ythier & Lourenço, 2022

Ythier, Eric & Lourenço, Wilson R., 2022, A new species of Lychas C. (Scorpiones: Buthidae) L. Koch, 1845 from Thailand, Faunitaxys (Oxford, England) 10 (26), pp. 1-7 : 2-3

Lychas chanthaburiensis sp. n.

( Fig. 1-2 , 4 -11, Tab. I )

ZooBank: http://zoobank.org/ 86FC3696-9D9E-4E2B-B890-26275CAF8848

Holotype, ♂, Thailand, Chanthaburi Province, Khao Khitchakut, J.- B. Lacroix leg. (No. 63), 1993, EY0205 ( EYPC), deposited in the Muséum national d’Histoire naturelle, Paris.

Etymology. – The specific name refers to the Province of Chanthaburi where the new species was collected.

Diagnosis. –Scorpion of medium size for the genus, with a total length of 46.9 mm for the adult male holotype. General coloration yellowish with metasomal segment V, telson and chela fingers reddish yellow; some greyish spots on the prosoma, tergites and metasoma; chelicerae with greyish variegated spots partially covering the dorsal surface; femur and patella of same color as chela hand, yellowish. Prosoma and tergites weakly to moderately granular, with carinae weakly marked. Sternites smooth except VII with weakly marked granulation on lateral sides and two vestigial carinae. Carapace moderately emarginated. Pectines long with 22-23 teeth. Metasoma elongated and slender; carinae weakly crenulate to smooth on I-III, weakly crenulate to vestigial on IV, vestigial on V;all intercarinal spaces smooth to weakly granular.Telson moderately elongated; subaculear tubercle strong and spinoid. Dentate margins of pedipalp chela fixed and movable fingers with 6-6 rows of granules; proximal row of granules with three isolated external accessory granules and one isolated internal accessory granule on fixed finger, three isolated externalaccessory granules on movable finger. External side of patella with trichobothria esb 1 and esb 2 at the same level.

Description (based on male holotype).

Coloration. – Basically yellowish with some dark pigmentation on body, metasoma and chela. Prosoma: carapace yellowish with a greyish inverted triangular spot at anterior margin, extending from lateral to median eyes; some greyish spots also on lateral and posterior edges; eyes surrounded by black pigment. Mesosoma : tergites yellowish with confluent greyish spots. Metasomal segments I-IV yellowish with ventral side marked distally with greyish spots; segment V reddish yellow without spots. Telson with vesicle reddish-yellow; aculeus reddish-yellow at base and reddish at its extremity. Venter pale yellow all over; genital operculum and pectines paler than sternites. Chelicerae yellowish, marked with greyish variegated spots which partially cover the dorsal surface; fingers yellowish entirely covered with greyish pigmentation, teeth reddish. Pedipalps: femur and patella yellowish; chela yellowish with fingers reddish yellow and rows of granules on dentate margins of fingers reddish. Legs pale yellow.

Morphology. – Prosoma: Carapace weakly to moderately granular with carinae weakly marked. Anterior margin of carapace moderately emarginated. Median ocular tubercle anterior to the centre of the carapace; median eyes separated by approximately one ocular diameter. Five pairs of lateral eyes (three major ocelli and 2 minor ocelli). Sternum triangular, longer than wide. Mesosoma : tergites weakly to moderately granular. Tergites I-VI with a median carina; weak to obsolete on I, weak to moderate on II-VI. Tergite VII pentacarinate, with lateral pairs of carinae moderate; median carinae present in proximal half, moderately developed. Sternites III to VI smooth; VII with a weakly marked granulation on lateral sides; spiracles elongated; sternite VII with two vestigial carinae. Pectines long; pectinal tooth count 22-23; fulcra present and conspicuous. Metasoma elongated and slender; segments I-II with 10 carinae, III-IV with 8 carinae, V with 5 carinae;segments I-III with dorsal and subdorsal carinae weakly crenulate, others smooth; intermediate carinae on segment II complete; segment IV with dorsal carinae weakly crenulate and other smooth to vestigial, segment V with all carinae vestigial, rounded; presence of one posterior spinoid granule on dorsal and subdorsal carinae of segments I-III; all intercarinal spaces smooth to weakly granular; Telson moderately elongated, smooth to weakly granular; three vestigial ventral carinae; aculeus strongly curved, shorter than vesicle; subaculear tubercle strong and spinoid. Chelicerae with dentition characteristic of buthids (Vachon, 1963); two reduced basal teeth on movable finger, not fused. Pedipalps: Femur pentacarinate; all carinae crenulate. Patella with seven carinae, crenulate; dorsointernal carinae with 6-7 spinoidgranules. Chela with carinae vestigial, rounded; intercarinal spaces smooth except few granules on internal face. Dentate margins on fixed and movable fingers composed of 6-6 rows of granules; one additional small apical row of 4 granules on movable finger; two accessory granules next two the terminal denticle on fixed and movable fingers; proximal row of granules with three isolated external accessory granules and one isolated internal accessory granule on fixed finger, three isolated external accessory granules on movable finger. Chela with a conspicuous scalloping of proximal dentate margin of fixed finger. Trichobothrial pattern of type A, orthobothriotaxic (Vachon, 1974); dorsal trichobothria of femur in β (beta) configuration (Vachon, 1975); patella trichobothria esb 1 and esb 2 at the same level. Legs: ventral aspect of tarsi densely equipped with two rows of setae; tibial spurs present on legs III and IV, moderately developed; pedal spurs present and moderately developed on all legs. Measurements in Table I .

Comparative material examined

Relationships.– Byitsgeneralmorphology, Lychas chanthaburiensis sp. n. shows several characters which associate it to Lychas mucronatus ( Fig. 3 ), a species also distributed in Thailand.

The new species can however be distinguished from L. mucronatus by the following main features:

(i) a much paler general coloration with body and appendages yellowish except metasomal segment V, telson and chela fingers reddish yellow and some greyish spots on the prosoma, tergites and metasoma. Pedipalp femur and patella are of same color as chela hand, uniformly yellowish (femur and patella with dark spots in L. mucronatus ). It should be noted that the specimen has not lost pigmentation (eg. under the effect of light exposure) and the pigmentation pattern is well visible where it is present;

(ii) chelicerae with greyish variegated spots only partially covering the dorsal surface (covering the whole surface in L. mucronatus );

(iii) prosoma, mesosoma and metasoma with all carinae much less marked and all intercarinal spaces much less granular. Sternite VII has only two vestigial carinae (four in L. mucronatus );

(iv) metasoma with all segments slenderer (see Tab. I );

(v) different trichobotrial pattern on external side of patella with trichobothria esb 1 and esb 2 at the same level (esb 1 proximal to esb 2 in L. mucronatus ).

By its general pale coloration, lacking pigmentation on pedipalp femur and patella as well as on legs, Lychas chanthaburiensis sp. n. can also be associated to Lychas aberlenci , a species distributed in Laos. Both species can however be distinguished notably by the following main features:

(i) chelicerae with greyish variegated spots only partially covering the dorsal surface (much darker pigmentation, covering the whole surface in L. aberlenci );

(ii) lower pectinal tooth count (29-30 in male L. aberlenci ); (iii) different morphometric ratios, notably the chela which are slenderer in L. aberlenci (see Tab. I );

(v) different trichobotrial pattern on external side of patella with trichobothria esb 1 and esb 2 at the same level (esb 1 proximal to esb 2 in L. aberlenci ).

Figures

Fig. 1-2. Lychas chanthaburiensis sp. n., ♂ holotype, habitus. 1. Dorsal aspect. 2. Ventral aspect.

Fig. 4- 10. Lychas chanthaburiensis sp. n., ♂ holotype (4-9) and L. mucronatus, ♂ from Laos (10). 4. Chelicera, dorsal aspect. 5-10. Trichobothrial pattern. 5-6. Chela, external (5) and ventral (6) aspects. 7. Femur, dorsal aspect. 8-9. Patella, dorsal (8) and external (9) aspects. 10. Patella of L. mucronatus, external aspect.

Fig. 3. Lychas mucronatus, adult ♂ from Thailand (Chiang Mai). See Lourenço, 2020 for habitus ofadult ♂ fromLaos and Vietnam.