Chaerilobuthus staxi Lourenço, 2024

Chaerilobuthus staxi Lourenço sp. n.

(Fig. 4- 11)

ZooBank:https://zoobank.org/ 6858EF51-4033-41D9-90F9-98B35CD1CF8D

Holotype. Most certainly a juvenile female. Type locality and horizon: Myanmar (Burma), Kachin; precise locality unknown; Lower Cretaceous.

Diagnosis. – General morphology shows similarities with other members of the family Chaerilobuthidae . Carapace not emarginated anteriorly; median eyes strongly reduced but represented by a macula and possible lens; two reduced lateral eyes. Pedipalps globally elongated; relationship between chela length vs chela width equal to 7.05 (Lourenço & Velten, 2022); spinoid granules absent from the internal aspect of patella. One pecten observed, not large with 5 teeth; fulcra absent; sternum pentagonal and conspicuous, slightly longer than wide; spiracles very small and rounded in shape; cheliceral dentition partially observed; movable finger with two distal teeth; distal teeth of fixed and movable fingers very long and overlapping for about one half of their length; fixed and movable fingers with one basal and one median tooth; vesicle bulbous with a moderately long aculeus. Trichobothrial pattern related to those of buthoids and chaeriloids, recalling types A and B, as defined by Vachon (1974) with at least 2 dorsal and 3-4 external trichobothria on the femur; 2 to 4 dorsal, 1 internal and 4-5 external on the patella; 2 dorsal and 2-3 external on chela hand and 4-5 on fixed finger.

Patronym. – Honours Dr Dietmar Stax (Pfungen, Switzerland) who arranged facilities for the study of the specimen.

Depository. – The type specimen is deposited in the Collection of Dr Dietmar Stax ( Pfungen, Switzerland) .

Description

Coloration. – The scorpion is reddish-yellow with some dark reddish zones; carapace, tergites and sternites reddish-yellow; metasomal segments dark reddish-yellow; telson reddish; pedipalps and legs reddish-yellow. Ventral aspect reddish-yellow; pecten yellow.

Morphology. – Carapace with some minute granulations anteriorly; almost smooth; anterior margin without any median concavity, close to straight. Carinae and furrows weak or absent. Median ocular tubercle partially collapsed by the process of dissection; however two reduced median eyes are more or less observable. Two lateral eyes can be observed. Sternum pentagonal and conspicuous, slightly longer than wide. Mesosomal tergites weakly granular as carapace and with inconspicuous carinae; VII with five moderately marked carinae. Pecten small with 5 teeth; fulcra absent; the zone with peg sensillae can be observed on tooth. Sternites can be observed but suffered with the dissection process; almost smooth, with rounded shaped spiracles. Metasomal segments I to IV with some well observable carinae; dorsal with spinoid granules; segment V with five carinae; ventral carinae on segments I-IV weakly marked; setation on segments I to V inconspicuous. Telson with a bulbous vesicle; weakly granular to smooth and a weak setation; aculeus long but moderately curved. Cheliceral dentition partially observed; movable finger with two distal teeth; distal teeth of fixed and movable fingers very long and overlapping for about one half of their length; fixed and movable fingers with one basal and one median tooth (Vachon, 1963). Pedipalps elongated; femur pentacarinate with 2-3 inconspicuous spinoid granules on internal face; patella with dorso-internal, ventrointernal, dorso-external, external and ventral carinae; spinoid granules on internal face inconspicuous. Chela with moderately to weakly marked carinae; all faces weakly granular to smooth; internal face without spinoid granules. Fixed and movable fingers with 6-7 longitudinal rows of small, rounded granules, separated by slightly bigger accessory granules; extremity of fingers with one stronger spinoid granule. Trichobothriotaxy: a trichobothrial pattern related to those of both buthoid and chaeriloids, types A and B can be observed (Vachon, 1974); for details see diagnosis. Leg tarsi with thin ventral setae. Pedal spurs present and moderately marked; tibial spurs absent.

Morphometric values (mm), holotype of Chaerilobuthus staxi Lourenço sp. n.

– Total length (including telson) 4.81.

– Carapace length 0.87; anterior width 0.59; posterior width 0.67.

– Mesosoma : 1.32.

– Metasomal segments

I: length 0.24, width 0.27;

II: length 0.27, width 0.26;

III: length 0.29, width 0.28;

IV: length 0.37, width 0.27;

V: length 0.67, width 0.32.

– Telson: 0.78.

– Vesicle: width 0.28.

– Pedipalp femur length 0.64, width 0.24;

patella length 0.65, width 0.21;

chela length 1.20, width 0.17;

movable finger length 0.64.

Relationships. – In account of the small size of pectines and of the conspicuous size of the sternum, the new species seems to be related to both Chaerilobuthus complexus Lourenço & Beigel, 2011 and Chaerilobuthus gigantosternus Lourenço, 2016 . The new species differs however, from these last two species by a combination of characters:

( i) anterior margin of carapace not emarginated,

( ii) presence of reduced median eyes,

( iii) spiracles round,

( iv) pedipalps globally elongated, in particular chelae; relationship between chela length vs chela width equal to 7.05; this value being only inferior to that of Chaerilobuthus brandti Lourenço, 2022 . For details refer to Lourenço & Velten (2022).