Chaerilobuthus bruckschi Lourenço, 2015

Xuan, Qiang, Prendini, Lorenzo, Engel, Michael S., Cai, Chenyang & Huang, Diying, 2025, Extinct scorpion family Chaerilobuthidae from Mid-Cretaceous Burmese amber reinterpreted as subfamily of extant family Pseudochactidae (Chelicerata: Scorpiones), Zoological Journal of the Linnean Society 203 (1), pp. 1-60 : 6-13

Chaerilobuthus bruckschi Lourenço, 2015

( Figs 4–10 )

Chaerilobuthus bruckschi Lourenço, 2015: 470 , 471, figs 13–18, photos 194–196.

Type material: Holotype: one juv. (sex unknown) (personal collection of KlausPeter Brucksch, Kuranda, Australia), Cretaceous (Cenomanian) burmite: MYANMAR: Kachin State (precise locality unknown).

Diagnosis: The following combination of characters is diagnostic for C. bruckschi : carapace anterior margin sublinear ( Figs 6A , 9A ); lateral ocelli markedly protruding ( Figs 6A , 9A ), pectines each with five or six teeth ( Fig. 6D ); pedipalp chela relatively slender, ratio of chela length: chela manus width less than 5 ( Fig. 10 ); ratio of metasomal segment IV: V length less than 2 ( Figs 5C, D, E, F , 9K, L, M, N ); metasomal segment V dorsolateral carinae slightly serrate ( Fig. 9M ); telson vesicle slightly bulbous ( Figs 5E, F , 9M, N ), aculeus moderately long and curved, base narrow ( Figs 5E, F , 9M, N ).

Description: Based on the material examined ( NIGP 201161, 201162).

Carapace: Anterior margin with few, short microsetae; anteromedian depression narrow, shallow; anterosubmedial depressions absent; lateral ocular carinae absent; posteromedian and posteromarginal sulci distinct; posterior margin slightly recurved medially; surfaces almost smooth to sparsely covered by microsetae ( Figs 4A , 6A , 9A ). Median ocular tubercle situated anteromedially; median ocelli absent; one pair of large posterolateral major lateral ocelli present ( Fig. 6A ).

Coxosternal region: Surface smooth, sparsely covered in macrosetae ( Fig. 5B ). Sternum not visible.

Chelicerae: Fixed finger and manus, prolateral and ventral surfaces each with long, dense setae ( Fig. 6B, C ). Moveable finger markedly overlapping fixed finger such that cheliceral dentition partly visible; moveable finger with long dorsal distal (dd) denticle, small dorsal subdistal denticle, stout dorsal median denticle, long ventral distal (vd) denticle, and three or four small ventral accessory (va) denticles; fixed finger with long distal denticle and small subdistal denticle. Moveable finger with prominent serrula comprising moderately long spinules in proximal three-quarters.

Pedipalps: Segments gracile ( Figs 7 , 10 ). Femur with four carinae evident; prodorsal, proventral, and retrodorsal carinae distinct, serrate; retroventral carinae smooth, costate. Patella with six carinae evident; prolateral surface, dorsoventral ‘vaulted’ projection (‘anterior process’) moderately developed with moderately developed pair of apophyses or tubercles (‘patellar spurs’), each possessing one macroseta; retrodorsal, retromedian, and retroventral carinae distinct, smooth, and costate; prodorsal carina incomplete, slightly granular, and obsolete proximally. Chela relatively gracile (CL/ CW = 5.83, Appendix 2); manus globose; chela with five carinae evident; digital carina distinct on fixed finger and manus; prodorsal carina moderately developed, comprising several spiniform granules; promedian carina distinct, comprising five or six prominent spiniform granules; proventral carinae obsolete, comprising few isolated granules; retroventral carina obsolete, smooth, and costate; dorsomedian, dorsal secondary, subdigital, retromedian and ventromedian carinae absent or obsolete. Chela finger dentition not visible. Trichobothrial pattern Type D, β configuration. Femur with 11 trichobothria visible, six d, two i and three e trichobothria, trichobothria d 1, d 2, d 4 and d 6 noticeably smaller than others (‘petite’); trichobothrium e 1 situated proximal to trichobothrium d 3; trichobothrium e 3 situated dorsal to trichobothrium d 6 ( Figs 7A , 10 ). Patella with nine trichobothria visible, including three d, one i, and five e trichobothria; trichobothrium i 1 situated distal to trichobothrium d 3 ( Figs 7A , 10 ). Chela with 12 trichobothria visible; fixed finger with two d, two e, and three i trichobothria; manus with four E and one V trichobothria; trichobothrium Et 1 situated distally on manus, almost aligned with, or proximal to, moveable finger condyle; trichobothrium eb situated on fixed finger, slightly distal to moveable finger condyle; trichobothrium esb situated medially to subdistally on fixed finger; trichobothrium V 2 situated distally on manus and near retroventral carina ( Figs 7B–D , 10 ).

Legs: Tibia lateral and ventral surfaces each with scattered macrosetae ( Figs 6I–L , 9F–I ). Basitarsi each with distinct pedal spurs and pair of spinule rows, comprising c. 10 relatively long spinules, distally. Ungues moderately long, distinctly curved; dactyl pronounced, pointed.

Pectines: Three marginal lamellae and four median lamellae ( Figs 6D , 9J ); surface sparsely covered in macrosetae; longitudinal suture between marginal and median lamellae distinct. Fulcra absent or obsolete. Teeth rounded; distal three-quarters of each tooth occupied by sensillar field.

Genital operculum: Not visible, covered by fissures and bubbles.

Mesosoma : Pretergites surfaces almost smooth ( Figs 5A , 6E , 9D ); post-tergites I– VI surfaces finely granular, acarinate ( Figs 5A , 6E , 9D ); tergite VII surface sparsely granular with four distinct carinae (paired dorsosubmedian and dorsolateral carinae) in posterior half of segment ( Fig. 6H ). Sternites surfaces smooth, with scattered macrosetae; posterior margins broadly recurved; respiratory spiracles (stigmata) small, ovoid to round ( Figs 6F , 9E ).

Metasoma: Segments I– V progressively increasing in length, I wider than long, others longer than wide ( Figs 4 , 8 ). Segments I– V lateral and ventral surfaces each with few, short macrosetae ( Figs 5C–F , 6H , 9K–N ); I– IV dorsal surfaces each with distinct depression ( Figs. 6H , 9K, L ). Segments I– III each with six distinct carinae (paired dorsosubmedian, dorsolateral and ventrolateral carinae), IV and V each with eight distinct carinae (paired dorsosubmedian, dorsolateral, ventrolateral and ventrosubmedian carinae); dorsosubmedian carinae distinct on all segments, markedly serrate, and converging posteriorly; dorsolateral carinae distinct, markedly serrate on segments I– III, moderately serrate on segments IV and V; ventrolateral carinae distinct, moderately serrate on segments I– IV, weakly serrate on V; ventrosubmedian carinae absent on segments I– III, obsolete on IV, distinct, moderately serrate, and converging posteriorly on V ( Figs 5C–F , 6H , 9K–N ).

Telson: Dorsal surface flat; lateral and ventral surfaces relatively smooth, with several macrosetae ( Figs 5E, F , 6G , 9M, N ); subaculear tubercle absent; prominent, moderately long subaculear setal pair.

Material examined: MYANMAR: Kachin State: Noije Bum near HukawngValley,preciselocalityunknown, Cretaceous (Cenomanian) burmite: 1 juv. (sex unknown), dextral pedipalp patella and chela ab - sent ( NIGP 201161 ), 1 juv. (sex unknown) ( NIGP 201162 ) .

Figures

Figure 4. Chaerilobuthus bruckschi Lourenço, 2015, one juv. (NIGP 201161), habitus under incident light. A, dorsal aspect. B, ventral aspect. Scale bar: 1 mm.

Figure 5. Chaerilobuthus bruckschi Lourenço, 2015, one juv. (NIGP 201161), morphology under epifluorescence. A, B, mesosoma and metasoma, dorsal and ventral aspects. C, D, metasomal segments I–IV, dorsal and ventral aspect. E, F, metasomal segment V and telson, dorsal and ventral aspects. Scale bars: 400 μm.

Figure 6. Chaerilobuthus bruckschi Lourenço, 2015, one juv. (NIGP 201161), morphology under confocal microscopy. A, carapace.B, C, chelicera, dorsal and ventral aspects.D, sinistral pecten, ventral aspect. E, tergites.F, sternites.G, telson. H, metasomal segments, dorsal aspect. I–L, legs I–IV tarsi, lateral aspect.Scale bars: 200 μm (A, E–H); 50 μm (B, C, I–L); 100 μm (D).

Figure 7. Chaerilobuthus bruckschi Lourenço, 2015, one juv. (NIGP 201161), pedipalp trichobothrial pattern under epifluorescence (A, B) and confocal microscopy (C, D). Scale bars:200 μm.

Figure 8. Chaerilobuthus bruckschi Lourenço, 2015, one juv. (NIGP 201162), habitus under incident light. A, dorsal aspect. B, ventral aspect. Scale bars:1 mm.

Figure 9. Chaerilobuthus bruckschi Lourenço, 2015, one juv. (NIGP 201162), morphology under confocal microscopy. A, carapace.B, sinistral pedipalp, ventral aspect.C, sinistral pedipalp, dorsal aspect. D, tergites. E, sternites VI and VII.F, G, leg III tarsus, dorsal and ventral aspects. H, I, leg IV tarsus, dorsal and ventral aspects.J, pectinal tooth, ventral aspect.K, L, metasomal segments I–IV, dorsal and ventral aspects.M, N, metasomal segment V and telson, dorsal and ventral aspects. Scale bars: 200 μm (A–D, K–N); 100 μm (E–I); 50 μm (J).

Figure 10. Chaerilobuthus bruckschi Lourenço, 2015, one juv.(NIGP 201162), micro-CT reconstruction of pedipalp trichobothrial pattern, dorsal, lateral and ventral aspects.A–D, chela.E, F, femur. G–J, patella. Scale bars: 500 μm.