Trypanothacus, Lowe & Kovařík & Stockmann & Šťáhlavský, 2019

Lowe, Graeme, Kovařík, František, Stockmann, Mark & Šťáhlavský, František, 2019, Trypanothacus gen. n., a new genus of burrowing scorpion from the Arabian Peninsula (Scorpiones: Buthidae), Euscorpius 277, pp. 1-30 : 3-5

Trypanothacus gen. n.

( Figs. 1–44 , 47–77 , 84–87 , 90–108 , 111–118 , Tables 1–2 ) http://zoobank.org/ urn:lsid:zoobank.org:act:

E0EABA52-8563-466A-970F-F874A38AEBDC

Buthacus: Hendrixson, 2006: 47–52 , figs. 4–5, plates 3–4 (in part); Kovařík et al., 2013: 3 (in part); Kovařík et al., 2016b: 2 (in part); Kovařík, 2018: 6–10 (in part).

TYPE SPECIES. Trypanothacus barnesi sp. n.

ETYMOLOGY. The generic epithet Trypanothacus (masculine) is formed so as to rhyme with Buthacus , presumably a closely allied genus. The latter is deconstructed into Greek terms: βους (bous) = ox, θυσία (thysia) = sacrifice; and Latin ending: acus = needle. Here we combine the last two morphemes with Greek τρυπάνι (trypáni) = drill, a reference to the habit of burrowing in more consolidated soils by these scorpions.

DISTRIBUTION. Saudi Arabia, Oman.

DIAGNOSIS. Medium-sized buthids ( Kovařík, 2009; Sissom, 1990), adults 40–60 mm long; carapace trapezoidal with straight anterior margin, without downward-sloped preocular area, surfaces with sparse to moderately dense, fine and coarse granulation interspersed with smooth areas, only anterior median carinae developed, other carinae obsolete, anterior area glossy in females; 5 lateral eyes in ‘ type 5’ pattern ( Loria & Prendini, 2014); chelicerae with typical buthid dentition ( Vachon, 1963), ventral aspect of fixed finger with two denticles; tergites I–VI with three short, granulose posterior carinae, not projecting beyond posterior margins; tergites I–II with lateral carinae inconspicuous; sternite VII with 2 pairs of weak to moderate carinae; pectines with fulcra, marginal and middle lamellae with dense fine reddish setae; female pectines reach or extend beyond distal end of coxa IV, pectinal tooth counts, ♂ 22–26, ♀ 15–22; hemispermatophore flagelliform, capsule in 3+1-lobe configuration, with 3 sperm hemiduct lobes well separated from flagellum, and small, knob-like basal lobe; sternum subtriangular; metasomal segments moderately robust, segment II as wide as others, segments I–III with 10 carinae, median lateral carinae complete on I, incomplete on II–III; ventromedian carinae on segments II–III well developed with strong denticles that are larger in females, segment V with enlarged lobate dentition on ventrolateral carinae; dorsal carinae of metasoma with sparse medium to long macrosetae in both sexes; telson vesicle bulbous, without subaculear tubercle, aculeus shorter than vesicle; pedipalps short relative to body, femur and patella as long as or shorter than carapace, chelae small with carinae reduced or obsolete, movable finger not more than 1.6 times ventral length of manus, dentate margin of movable finger armed with 7–9 non-imbricated linear subrows of primary denticles or granules, each subrow flanked by internal and external accessory denticles, 3–6 subterminal denticles; males without recess or scalloping of dentate margins at base of pedipalp fingers, chela manus broader than in females; trichobothrial pattern orthobothriotaxic type A ( Vachon, 1974); femur with dorsal trichobothria in ss-configuration ( Vachon, 1975), petite trichobothrium d 2 located on dorsal surface, e 2 distal to d 5; patella with 7 external, 5 dorsal, and 1 internal trichobothrium, patella d 2 present, d 3 positioned internal to dorsomedian carina; manus with V 1 - V 2 axis nearly collinear with long axis of chela, fixed finger with db on proximal part of finger between esb and est, it located near tip; legs moderately robust, tibial spurs present on legs III– IV, but spurs may be reduced or absent on leg III; basitarsi I–III compressed, equipped with retrosuperior bristle-comb of macrosetae about as wide as segment, soles of telotarsi with ca. 5–10 unpaired macrosetae near mid-ventral axis, tarsal ungues of moderate to short length, strongly curved and tapered.

AFFINITIES. The ss-configuration of femoral trichobothria, internal position of patella d 3, and 3+1-lobe configuration of hemispermatophore capsule place Trypanothacus gen. n. firmly in the ‘ Buthus group’, an Old World clade distributed across semi-arid and arid Palaearctic lands ( Fet et al, 2005; Kovařík et al., 2016a). Within this group, Trypanothacus gen. n. is morphologically similar to Buthacus Birula, 1908 (under which one of its species was originally described) and Vachoniolus Levy et al., 1973 . Characters shared by these genera include reduced or obsolete carapacial carination, weakly granular, almost smooth tergites with three short carinae, short pedipalps with reduced carination and fingers bearing linear granule rows with internal and variable external accessory denticles, metasomal segments rather elongate, nearly uniform in width, with variably denticulate ventromedian/ ventrolateral carinae on segments II–III and V, and basitarsal bristle-combs. However, Buthacus and Vachoniolus are differentiated by the shape of the telson, which has a somewhat pyriform vesicle and a long, curved aculeus (aculeus L/ vesicle L 0.74–1.24). This contrasts with the more bulbous vesicle and shorter aculeus of Trypanothacus gen. n. (aculeus L/ vesicle L 0.59–0.76) ( Figs. 15–16 , 24, 27 , 41– 42, 45–46 , 96, 103 , 107 ). Compared to Trypanothacus gen. n., Buthacus and Vachoniolus may in some cases also have more slender legs and metasoma, denser setation on dorsal metasomal carinae and soles of telotarsi, and more expansive bristle-combs wider than the basitarsus. Vachoniolus is further distingushed by femoral trichobothrium e 2 placed approximately level with or proximal to d 5, and by pronounced sexual dimorphism of pedipalp chelae which are swollen in adult males ( Levy et al., 1973; Vachon, 1979; Lowe, 2010b). Apart from these differences, a close relationship of this triad of genera is suggested by the similarity of the hemispermatophore capsules which all have fairly long, lanceolate posterior lobes, and small knob-like basal lobes ( Figs. 74–76 , 78–81 ) (see also Levy et al., 1973; Levy & Amitai, 1980; Vachon, 1949, 1952, 1953; Lowe, 2010b). Trypanothacus gen. n. bears some outward resemblance to Odontobuthus Vachon, 1950 , which also occurs in Oman, and more widely in Iran, Iraq and Pakistan. Both genera have tricarinate tergites, robust legs and metasoma, enlarged dentition on ventromedian carinae of metasoma II–III and ventrolateral carinae of metasoma V, and a bulbous telson with relatively short, stout aculeus. However, Odontobuthus is differentiated by: (i) strongly developed carination on the carapace, with distinct central lateral carinae joined to posterior median carinae in a lyre configuration (vs. obsolete carination in Trypanothacus gen. n.); and (ii) hemispermatophore basal lobe a well defined, digitate hook ( Lowe, 2010a), that is quite different from the small knob- like protuberance of Trypanothacus gen. n., Buthacus and Vachoniolus . Similar parallels and contrasts can be noted when comparing Trypanothacus gen. n. to Buthus Leach, 1815 , another widespread Old World genus of burrowing buthids.

SUBORDINATE TAXA. Trypanothacus barnesi sp. n. and T. buettikeri ( Hendrixson, 2006) comb. n..

COMMENTS. We discuss a few other species of Buthacus that have been linked to Buthacus buettikeri on the basis of diagnostic characters of the metasoma and telson, that may justify transferring them to Trypanothacus gen. n..

(1) Lourenço (2006) incorrectly restored Buthacus tadmorensis ( Simon, 1892) of Palmyra, Syria, which was synonymized under Buthacus macrocentrus (Ehrenberg, 1828) by Kovařík (2005), arguing that the former is distinguished by strongly developed ventromedian carinae on metasoma II–III with enlarged denticles, a character that Simon (1982) cited in his description. However, the Palmyra specimens examined by Lourenço (2006) were characterized only as “... possibly part of the type material of Simon”, leaving ambiguity about the identity of this species. The opinion was expressed that Buthacus leptochelys nitzani Levy, Amitai & Shulov, 1973 , a relatively robust form, could be a junior synonym of B. tadmorensis .

Lourenço & Qi (2006) remarked that B. buettikeri was similar to, and could be a “regional morph” or synonym of B. tadmorensis , because “... the areas of distribution of B. tadmorensis and Buthacus buettikeri are not very much distinct ...”. The latter claim is questionable. Palmyra is far from the localities in central Saudi Arabia where we have confirmed T. buettikeri resides based on our restudy of the type series. A few other types from a single, disjunct northern site near the Saudi Arabia-Jordan border, closer to Syria, have not been restudied and their taxonomic status remains unclear (see below). The posterior metasoma and telson of a male from Palmyra labeled as “ B. tadmorensis ” was illustrated in lateral view by Lourenço (2006: 63, fig. 18). If this figure is accurate, the enlarged denticles on ventromedian carinae of metasoma III and ventrolateral carinae of metasoma V are consistent with T. buettikeri , but the more slender segments (metasoma IV L/D 2.12, V L/D 2.7), denser setation on dorsal metasomal carinae and ventral telson vesicle, and the less bulbous telson with longer aculeus, are not.

(2) Lourenço & Qi (2006) described Buthacus pakistanensis from the Thar Desert of Pakistan. The ventromedian carinae on metasoma II–III and ventrolateral carinae on V are strongly developed, with enlarged teeth in females. The telson is less pyriform, more bulbous, and has a shorter, less strongly curved aculeus compared to other Buthacus spp. The authors noted that this species was similar to “ B. tadmorensis ”.

(3) Lourenço & Leguin (2009) described Buthacus williamsi based on three females collected from the United Arab Emirates in the region of Fujairah; males are unknown. It was suggested to be related to B. buettikeri , with which it shares characters of enlarged dentition on ventromedian carinae on metasoma II–III and ventrolateral carinae on V, and a telson with relatively bulbous vesicle and shorter aculeus compared to other Buthacus spp. However, it stands apart from both Buthacus and Trypanothacus gen. n. in having very short pectines in females, whose apical ends fall well short of the distal limits of coxae IV, and a low pectinal tooth count (13–14) below any recorded from either of those two genera.

Although the aforementioned species bear some similarities to T. buettikeri comb. n., and T. barnesi sp. n., until we can analyze and confirm materials of those species we take a conservative approach and limit the scope of the genus to the two species that we have so far examined. Trypanothacus gen. n. may represent a specialized lineage of the Buthacus - complex of psammophiles, that became secondarily adapted to burrowing in firmer substrates. Functional convergence may account for the metasoma and telson structure being similar those of other pelophilous or semi-psammophilous buthids (e.g. Buthus , Odontobuthus ), or of other more robust Buthacus -complex species like those discussed above. Future molecular studies (in preparation) should assist in elucidating its phylogenetic position.

Figures

Figures 1–4: Trypanothacus barnesi gen. et sp. n. Figures 1–2. Male paratype from the type locality in dorsal (1) and ventral (2) views. Figures 3–4: Female paratype from the type locality in dorsal (3) and ventral (4) views. Scale bar: 10 mm.

Figures 5–10: Trypanothacus barnesi gen. et sp. n. Figures 5, 7, 9. Male holotype, carapace and tergites I–V (5), coxosternal area and sternites (7), right legs I–IV, retrolateral aspect (9.I–IV). Figures 6, 8, 10. Female paratype from the type locality, carapace and tergites I–III (6), coxosternal area and sternites III–IV (8), right legs III–IV, retrolateral aspect (10.III–IV).

Figures 11–12: Trypanothacus barnesi gen. et sp. n. Male paratype from Thumrait (VII.1997), carapace and tergites I–VII (11), coxosternal area and sternites (12). UV fluorescence. Scale bars: 2 mm.

Figures 13–14: Trypanothacus barnesi gen. et sp. n. Female paratype from Yalooni (XII.1988), carapace and tergites I–VII (13), coxosternal area and sternites (14). UV fluorescence. Scale bar: 2 mm.

Figures 15–22: Trypanothacus barnesi gen. et sp. n. Figures 15, 20–22. Male holotype, metasoma V and telson lateral view (15), metasoma and telson lateral (20), ventral (21), and dorsal (22) views. Figures. 16–19. Female paratype from type locality, metasoma V and telson lateral view (16), metasoma and telson lateral (17), ventral (18), and dorsal (19) views. Scale bars: 4 mm (17–19, 20–21).

Figures 23–28: Trypanothacus barnesi gen. et sp. n. Figures 23–25. Male paratype from Thumrait (VII.1997), metasoma and telson dorsal (23), lateral (24) and ventral (25) views. Figures 26–28. Female paratype from Yalooni (XII.1988), metasoma and telson dorsal (26), lateral (27) and ventral (28) views. UV fluorescence. Scale bar: 4 mm.

Figures 29–46: Figures 29–42: Trypanothacus barnesi gen. et sp. n. Figures 29–40. Pedipalp segments. Figures 29–38. Male holotype, chela dorsal (29), external (30), and ventral (31) views. Patella dorsal (32), external (33) and ventral (34) views. Femur and trochanter internal (35), dorsal (36), and ventral (37) views. Movable finger dentition (38). Trichobothrial pattern is indicated in Figures 30–33 and 35–36. Figures 39– 40. Female paratype from the type locality, chela dorsal (39) and external (40) views. Figures 41–42. Telson, male holotype (41) and female paratype from type locality (42), lateral views. Figures 43–44: T. buettikeri comb. n., pedipalp chela dorsal, male holotype (43) and female paratype (44). Figures 45–46: Buthacus stockmanni Kovařík et al., 2016, telson, male holotype (45) and female paratype (46), lateral views.

Figures 47–58: Trypanothacus barnesi gen. et sp. n. Pedipalp segments of male paratype from Thumrait (VII.1997), chela dorsal (47), external (48), ventral (49) and internal (50) views. Patella dorsal (51), external (52), ventral (53) and internal (54) views. Femur and trochanter dorsal (55), external (56), ventral (57) and internal (58) views. UV fluorescence. Scale bar: 2 mm.

Figures 59–70: Trypanothacus barnesi gen. et sp. n. Pedipalp segments of female paratypes, chela dorsal (59), external (60), ventral (61) and internal (62) views. Patella dorsal (63), external (64), ventral (65) and internal (66) views. Femur and trochanter dorsal (67), external (68), ventral (69) and internal (70) views. Dorsal views (59, 63, 67): paratype female from Thumrait (XI.1989) (with normal dorsointernal carina on femur). External (60, 64, 68), ventral (61, 65, 69) and internal (62, 66, 70) views: paratype female from Yalooni (XII.1988) (with malformed dorsointernal carina on femur). UV fluorescence. Scale bars: 2 mm (59, 63, 67), 2 mm (60–62, 64–66, 69–70).

Figures 71–77: Trypanothacus barnesi gen. et sp. n. Figures 71–73. Paratype male, right chelicera, dorsal (71), ventral (72) and ventral UV fluorescence (73) views. Scale bar: 1 mm. Figures 74–77. Holotype male, right hemispermatophore, capsule region with lobes in anterior (74), convex compressed (75) and posterior (76) views, and whole hemispermatophore in convex view (77). Scale bars: 1 mm (71–73), 500 µm (74–76), 1 mm (77).

Figures 84–85: Trypanothacus barnesi gen. et sp. n., in vivo habitus, male holotype (84) and female paratype from type locality (85).

Figures 86–89: Trypanothacus barnesi gen. et sp. n.. Figures 86–87. Male (86) and female (87) from Thumrait, photos by J. N. Barnes. Figures 88–89. Type locality, Oman, S of Schelim, 18.041070°N 55.612262°E.

Figures 90–93: Trypanothacus buettikeri comb. n. Figures 90–91. Male holotype in dorsal (90) and ventral (91) views. Figures 92–93: Female paratype in dorsal (92) and ventral (93) views. Scale bars: 10 mm.

Figures 94–95: Trypanothacus buettikeri comb. n. Male holotype, carapace and tergites I–IV (94), coxosternal area and sternites I–II (95). UV fluorescence. Scale bar: 2 mm.

Figures 96–106: Trypanothacus buettikeri comb. n. Figures 96–101. Male holotype, lateral view of metasoma and telson (96), dorsal views of pedipalp chela (97) patella (98) and femur (99), external views of pedipalp chela (100) and patella (101). Figure 102. Male from Wadi Turabah (NHMB No. 509), dorsal view of pedipalp patella. Figures 103–106. Female paratype (NHMB 896), lateral views of metasoma (103) and pedipalp chela (104), dorsal view ofpedipalp patella (105) and femur (106).UV fluorescence.Scale bars:2 mm (96), 2 mm (97–101), 2 mm (102), 2 mm (103), 2 mm (104–106).

Figures 107–110: Morphometric scaling relations of the telson of fossorial ‘Buthus group’ scorpions. Figure 107. Double logarithmic scatterplot of telson vesicle length/ depth (L/ D) ratio vs. aculeus length normalized to vesicle length (aculeus L/ vesicle L), for large pelophiles/ semipsammophiles (4 genera, 53 species) (Buthus, Odontobuthus, Pantobuthus: orange circles; Trypanothacus gen. n.: blue circles) and large psammophiles/ ultrapsammophiles (6 genera, 29 species) (Buthacus: cyan circles; Vachoniolus: dark green circles; Apistobuthus, Buthiscus, Liobuthus, and Plesiobuthus: yellow circles). Dark line: linear least squares regression fit to all data shown (Pearson correlation coefficient, R = 0.57). Upper right inset: diagram of measurements estimated from inverted telson lateral profiles, with dorsal surface of vesicle approximately leveled; SA = ventral profile length of aculeus from base point to tip, LV = length of vesicle from anterior limit or inflection point to aculeus base point; HV = vesicle depth or height (distance between dorsal and ventral tangent planes). Base point was placed at local minimum of inverted ventral profile curve. SA was calculated by cubic spline fit (>10 anchor points). For a minority of broken tips, SA was estimated by intersecting extrapolated dorsal and ventral profile curves (<5%). Figure 108. Scatterplot of fossorial buthids in Figure 107, superposed upon larger scale plot of Order Scorpiones (gray circles). Gray line: linear least squares regression fit to Order Scorpiones data (including data in Figure 107) (Pearson correlation coefficient, R = –0.62).Also plotted are data from small ‘Buthus group’ psammophiles/ ultrapsammophiles (5 genera, 10 species: Compsobuthus arabicus, Lanzatus somalilandus, Neobuthus kutcheri, Picobuthus dundoni, P. wahibaensis, Anomalobuthus krivochatskyi, A. pavlovskyi, A. rickmersi, A. lowei, A. talebii) (dark yellow circles). Figure 109. Double logarithmic scatterplot of carapace length (L) vs. aculeus length normalized to vesicle length (i.e., aculeus L/ vesicle L) for psammophile/ ultrapsammophile members of the ‘Buthus group’, including large species in Figure 107, and small species in Figure 108 (dark yellow circles). Blue line: linear least squares regression fit to all data shown (Pearson correlation coefficient, R = 0.74). Figure 110. Scatterplot of psammophile buthid data in Figure 109 (all in one color, blue circles) superposed upon larger scale plot of Order Scorpiones (gray circles). Gray line: linear least squares regression to Order Scorpiones data (including data in Figure 109) (Pearson correlation coefficient, R = –0.01). Also plotted are data from bothriurid genus Brachistosternus (43 species) (magenta triangles), and corresponding linear least squares regression fit (R = 0.39). All plots in Figures 107-110 include data from both males and females. Data were assembled by mining taxonomic literature or directly measuring specimens. Included are 1854 species or subspecies (1331 ♂, 1201 ♀) representing all known extant genera (1841 species or subspecies) plus 7 fossil genera (13 species).

Figures 111–113: Trypanothacus barnesi gen. et sp. n., mitotic metaphase (111), postpachytene (112) and ideogram (113) (y axis - % of the chromosome length of the haploid set) of male holotype. Scale bar = 5 μm.

Figures 114–116: Trypanothacus barnesi gen. et sp. n., promenade à deux (courtship dance) in a mating pair of individuals collected from the type locality. Photos taken in laboratory. Male is on the right.

Figures 117–118: Trypanothacus barnesi gen. et sp. n., cheliceral massage (117) and spermatophore deposition (118) in a mating pair of individuals collected from the type locality. Photos taken in laboratory. Male is on the right.

Figures 78–83: Hemispermatophore capsule regions and lobes of buthid genera presumed to be closely related to Trypanothacus gen. n.. Figures 78–79:Buthacus stockmanni Kovařík,Lowe et Šťáhlavský, 2016(topoparatype male,N.ofZag,Morocco).Figures80–81:Buthacus nigroaculeatus Levy, Amitai et Shulov, 1973 (Wadi Muqshin, Montesar, Oman, 30.III.1989, leg. A.S. Gardner). Figures 82–83: Vachoniolus globimanus Levy, Amitai et Shulov, 1973 (Ramlat As Sahmah, Oman, 7.X.1994, leg. G. Lowe & M.D. Gallagher). All figures right capsule except Figures 78–79 (mirrored left).Anterior (78, 81–82) and convex compressed (79–80, 83) views. Scale bars: 400 µm (78–79), 400 µm (80–81), 400 µm (82–83).