Xenobuthus xanthus Lowe 2018, sp. n.
Creators: name: Lowe, Graeme
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Scorpiones
Buthidae
Xenobuthus
Xenobuthus xanthus

description: Xenobuthus xanthus sp. n.
(Figs. 151–162, 260–325, 328–329, 335, 338, Tabs. 3, 7) http://zoobank.org/urn:lsid:zoobank.org:act:6BA2FD27- C501-4025-B258-2B7FB1F912D0
Butheolus anthracinus: Lowe, 2010a: 23.
HOLOTYPE. Holotype ♂, Jabal Zulul, escarpment above Ash Shuwaymiyah, UV detection, on ground, silt and gravel, rocky bowl surrounded by rocky cliffs and slopes, partly disturbed by earthmoving equipment, 17° 57.12'N 55°39.28'E, 215 m a.s.l., 26.IX.1995, 00:45 h, leg. G. Lowe, M.D. Gallagher (NHMB).
PARATYPES. 2 juv ♂, same locality as holotype; 1 subadult ♀, Jabal Qara, north slopes, Nejd Desert, UV detection, rocky wadi and rocky slopes, 17°17.83'N 54°05.11'E, 800 m a.s.l., 16.X.1993, 22:38 h, leg. G. Lowe (MNHN); 1♀, Wadi Ara, Jabal Samhan, under rocks at base of cliff, 17°16'N 54°57'E, 1050 m a.s.l., 2 Feb 1994, leg. M. R. Brown (ONHM); 1♀, Wadi Shuwaymiyah, under rock on mound of sandy soil, near permanent water seepage site on northern edge of wide vegetated wadi, 17°55.94'N 55°31.47'E, 50 m a.s.l., 2 5.IX.1995, 19:15 h, leg. G. Lowe, M.D. Gallagher (NHMB); 1 subadult ♀, Wadi Shuwaymiyah, small rocky wadi, UV detection on patch of coarse sand on ground, in small side wadi, gravel with rocky walls, 17°55.81'N 55°32.98'E, 45 m a.s.l., 25.IX.1995, 21:30 h, leg. G. Lowe, M.D. Gallagher (BMNH); 1 subadult ♀, 1 juv ♂, east of Jabal Qamr, along coastal wadi, UV detection on slope, vegetated slopes with rocks; soil suitable for burrowing;, 16°53.71'N 53°48.75'E, 15 m a.s.l., 28.IX.1995, 00:30 h, leg. G. Lowe, M.D. Gallagher (NHMB).
DIAGNOSIS. A member of the genus Xenobuthus differentiated as follows: bicolored, with base color bright yellow, metasomal segments I–III yellow, metasoma IV yellow or dark brown, metasoma V and telson dark brown to black; pedipalp and legs yellow; carapace and tergites with moderately sparse, coarse granulation; metasoma IV without lateral median carinae; metasoma V with ventromedian carina composed of single series of granules, not posteriorly bifurcate, males with ventral intercarinal surface smooth on posterior 1/4 of segment; posterior metasomal segments relatively narrow in male: metasoma III L/W ♂ 1.21; metasoma IV L/W ♂ 1.52; metasoma V L/W ♂ 1.92, L/D 2.44.
ETYMOLOGY. From Greek ξανθός (xanthós) meaning yellow, a reference to the body color.
DESCRIPTION.
Based on holotype adult ♂, 3 juv ♂, 2 adult ♀, 3 juv ♀ from Dhofar, Oman.
Coloration (Figs. 260–294, 313–316, 320–325). Bicolored; base color bright yellow with dark brown or black metasoma V and telson; metasoma IV variably pigmented, ranging from bright yellow, to light brown, to dark brown; if dark brown, anterior end may be slightly lighter; median and lateral eyes dark; small brown spots on distal ends of leg femora and patellae marking prolateral articular condyles; chelicerae yellow, without reticulated markings; juveniles may have light fuscous patterns on carapace, tergites and pedipalps (Fig. 270).
Carapace (Figs. 262, 264, 266, 2 68, 270, 328–329). Strongly trapezoidal, W/L 1.15–1.23, posterior W/ anterior W 2.21 –2.41; lateral flanks steeply sloped; median ocular tubercle prominent; postocular area forming triangular posteromedial plateau with shallow depressions; interocular triangle gently sloped downwards towards anterior margin, less so in female; anterior margin with 7–9 macrosetae, carapace otherwise devoid of macrosetae; anterolateral margins with 5 pairs of lateral eyes: 3 major ocelli and 1 minor ocellus below granular ridge, and 1 minor ocellus above granular ridge; all carinae of carapace obsolete except for superciliary carinae which may extend slightly anterior to median ocular tubercle; central median and posterior median carinae indicated by granule rows along edges of postocular plateau; surface with sparse to moderate irregular coarse granulation, with extensive smooth areas in postocular plateau, posterior transverse and posterior marginal furrows, and median interocular triangle; superciliary carinae smooth, with a few coarse granules on posterior slopes; granulation of female carapace similar to male, weaker on interocular triangle.
Chelicerae (Figs. 260–261). Dorsal surface of manus smooth, with two short, pale microsetae on apical margin, each with adjacent granules; dorsointernal carina strong, granulate, bearing one long, dark macroseta and one short, pale microseta; fingers robust, movable finger dorsal margin with two large subdistal denticles and two small basal denticles, ventral margin with larger subdistal and smaller basal denticles, fixed finger with large subdistal denticle and proximal bicusp, two denticles on ventral surface; dorsal surface of movable finger smooth, with 2–3 pale microsetae.
Coxosternal area (Figs. 263, 265, 267, 269). Holotype male. Coxa I with medium to coarse granulation, endite smooth on distal third, coarsely granulated on posterior 2/3; coxa II with medium granules concentrated along margins, central surfaces sparsely granulated, endite smooth on anterior end and medial margin, granulated elsewhere; coxa III with strong peglike granulation concentrated along anterior and distal margins, posterior margin weakly granular in proximal half, central area of sclerite with sparse, fine granulation; coxa IV with dense band of strong peg-like granulation along anterior margin, rimmed with row of similar granules along proximal half of posterior margin, central surface very weakly shagreened; coxae I–III with scattered, mostly anterior macrosetae: coxa I 4–5, II 7–8, III 4–5; coxa IV with single macroseta on anterior proximal limit; sternum with weak fine granulation, subtriangular, with deep posteromedian pit, bearing 2 macrosetae; genital opercula with very weak fine granulation on anterior margin, otherwise smooth, with 2–4 macrosetae, posterolateral margins weakly concave. Females. Coxa I with heavy coarse granulation, distal part of endite smooth; coxa II with coarse granules in longitudinal strip on endite, medial half of endite smooth; distal, anterior and posterior margins coarsely granular, central area smooth; coxa III strongly granulated on anterior and distal margins, weakly granulated on proximal posterior margin, central area smooth; coxa IV with dense strip of granules on anterior margin, linear row of granules rimming proximal 2/3 of posterior margin, central area and distal margin smooth; coxal macrosetae: I 5–6, II 7–9, III 4–6, IV 1; sternum similar to male, weakly, finely granulate with larger median pit, 2 setae; genital opercula smooth, bearing 4–7 macrosetae.
Pectines (Figs. 263, 265, 267, 269). Basal piece with anterior margin concave, with deep median pit or groove; surface in male nearly flat, weakly shagreened, bearing 2 setae, in female strongly biconcave posteriorly, sparsely granulated in depressions, more densely along posterior margin, bearing 4–5 setae; pectines with 3 marginal lamellae, 6–8 middle lamellae, extending to distal end of coxa IV in male, falling short of distal end in female; marginal and middle lamellae with sparse cover of short macrosetae; fulcra with 1–4 fine macrosetae (mostly 3); teeth of similar length in both sexes, slightly longer in male; tooth counts: ♂ 18–21, ♀ 18–20.
Hemispermatophore (Figs. 317–319). Flagelliform, with elongate trunk; flagellum with short pars recta bearing anterior marginal lamella, longer pars reflecta gradually tapering to cylindrical hyaline filament; sperm hemiduct tripartite, posterior lobe large, laminate, median lobe small, acuminate, anterior lobe of intermediate length; posterior margin of median lobe overhanging posterior lobe, the two lobes fused along median lobe carina; basal lobe a low, moderately broad, axially oriented, curved scoop with posterior-facing concavity, arising from median lobe carina. The hemispermatophores extracted from the holotype male were soft, not well sclerotized, but the essential capsule structure and form of the basal lobe were visible.
Mesosoma (Figs. 262–270, 335). Tergites: pretergites smooth, with weak, fine corrugations on posterior margins; tergites I–VI with lateral areas of coarse granulation and smooth transverse patches, anterior lateral and medial areas weakly shagreened, posterior margins of sclerites rimmed by regular rows of granules; tergite I without distinct carinae, II with weak trace of median carinae; tergites III–VI tricarinate with anteriorly divergent, granulate carinae; granulation and carination pattern of female similar to male, but granules weaker in females; tergite VII with 5 carinae, median carina a weakly granulated hump, lateral carinae strongly granular, inner lateral carinae anteriorly divergent, intercarinal areas smooth except for a few coarse granules and a pair of anterior clusters of small granules; all tergites lacking macrosetae; sternites: holotype male: sternites III–V lacking carinae, medially smooth, weakly shagreened laterally, III densely shagreened on surface covered by pectines; sternites IV–VI with weak, smooth remnants of outer lateral carinae near posterior margins, adjacent to spiracles; sternites IV–VI with wide, posteromedian smooth patch; posterior margins of sternites III–VI with fringe of small, non-contiguous, digitate denticles; sternite VII smooth except for sparse fine granulation on mediolateral and outer lateral areas, median carinae smooth with trace of granulation, lateral carinae strongly granulose; carinae confined to posterior 2/3 of sternite, only median pairs extending to posterior margin; non-marginal macrosetae: III 18 along edges of pectinal contact area, IV 9, V 6, VI 8, VII 6 including 4 stereotypic isolated macrosetae in middle or anterior near outer sides of carinae; females: sternite III smooth except for finely shagreened areas on surface covered by pectines; sternites IV–VI smooth except for very weakly shagreened anterior lateral corners adjacent to presternite borders; sternite VII smooth; carinae obsolete on sternites III–V, reduced to smooth posterior wrinkles on medial sides of spiracles on VI; posterior marginal denticles of sternites III–VI much smaller than in males; sternite VII with two pairs of carinae, medial pair smooth, lateral pair smooth anteriorly, weakly granulate posteriorly; non-marginal macrosetae: III 24–27, IV 10- 13, V 6–10, VI 6–7, VII 6; mesosoma wider in female than male.
Metasoma (Figs. 262–263, 266–267, 270, 320– 325). Length about equal to prosoma and mesosoma, metasoma + telson L/ carapace L ♂ 5.62, ♀ 4.95–5.07; segments moderately robust; carination: segment I with 10 complete carinae, II with 10 carinae, 8 complete, lateral median carinae distinct only on posterior 3/4, III with 10 carinae, 8 complete, lateral median carinae distinct only on posterior 1/2, IV with 8 carinae, lateral median carinae absent, V with 3 carinae; most carinae granulate or weakly crenulate; in male, ventrolateral and ventromedian carinae on segment I weakly granular; in females, ventrolateral and ventromedian carinae on segment I smooth, on segment II weakly granular, more smooth anteriorly; ventrolateral carinae on segment V with gradual, slight increase in size of granules posteriorly; segment V with ventromedian carinae composed of linear series of granules, not bifurcating, ventrosubmedian carinae indistinct, positions only indicated by granules; lateral anal margin with 2 blunt granules or lobes, ventral anal margin with 13–20 granules; intercarinal surfaces: lateral and ventral aspects of segments I–IV mostly smooth with sparse granulation or isolated granules; dorsolateral and lateral surfaces of segments II–VI weakly rugose; segment V with sparse coarse granulation on ventral surface, smooth on lateral surface, male with posterior 1/4 of ventral surface smooth on either side of ventromedian carina; dorsal surfaces of all segments smooth in male, smooth or weakly rugose in female; setation: all segments equipped with scattered long, curved, golden macrosetae on all aspects, most located near or on carinae, setae of similar length in both sexes; metasoma V dorsolateral margins with 15 macrosetae in male, 7–11 in females.
Telson (Figs. 262–263, 266–267, 270, 320–325). Vesicle smooth dorsally and laterally, mostly smooth ventrally except for a few granules at anterior end; small indentations at setal insertion points; bulbous, with steep posterior slope, subaculear tubercle absent, but slight ridge indicates trace of tubercle; several long macrosetae on lateral and ventral surfaces; aculeus slightly shorter than vesicle.
Pedipalps (Figs. 271–312). Male (Figs. 271–282, 295–297, 301–304, 307–309). Femur: L/ W 2.87; dorsointernal, dorsoexternal and ventrointernal carinae strong, with regular coarse granulation; external carina a broad ridge, smooth or with isolated weak granules; internal carina moderate, with coarse granules; intercarinal surfaces smooth; 9–10 accessory macrosetae on distal external surface; patella: L/ W 2.87; dorsointernal, dorsomedian and external carinae moderate, smooth; dorsoexternal carina weak, smooth; internal carina moderate, weakly granulated; other carinae obsolete, ventromedian and ventroexternal carinae barely visible as smooth traces of thickened integument; intercarinal surfaces smooth; chela: slender, L/ W 4.26, all carinae obsolete, surface smooth with sparse macrosetae and microsetae; 9 primary denticle subrows on movable fingers, 8 on fixed fingers, total count of non-enlarged primary denticles on movable fingers 43–51 (N = 4 fingers), on fixed fingers 40–52 (N = 3 fingers, 1 malformed finger excluded); denticle subrows except proximal flanked by internal and external accessory denticles, 6–9 internal or external accessory denticles on movable finger, 7–8 on fixed finger. Female (Figs. 283–294, 298–300, 305–306, 310–312). Femur: slightly more slender than male, L/ W 3.00 –3.05; carination and surface texture similar to male; 9–11 accessory macrosetae on distal external surface; patella: slightly more robust than male, L/ W 2.71 –2.84; internal carina smooth, other carinae also smooth, as in male; intercarinal surfaces smooth; chela: more slender than male, L/ W 4.48 –4.71, all carinae obsolete, surface smooth with sparse macrosetae and microsetae; 9–10 primary denticle subrows on movable fingers, 8–9 on fixed fingers, total count of non-enlarged primary denticles on movable fingers 47–55 (N = 8 fingers), on fixed fingers 42–52 (N = 8 fingers); 8–9 internal or external accessory denticles on movable fingers, 7–9 on fixed finger. Trichobothriotaxy: orthobothriotaxic, type Aβ (Vachon, 1974) (Figs. 295–312).
Legs (Figs. 262–263, 266–267, 313–316). Inferior carinae finely serrate-denticulate on femora, other carinae on femora weakly, finely granulate; prolateral surfaces of femora with sparse fine granulation proximally, smooth distally, carinae in females becoming indistinct in proximal granular areas; patellae with weakly crenulate-denticulate inferior carinae, other carinae smooth, prolateral surfaces smooth; tibia III–IV with spurs; retrolateral tarsal spurs simple, prolateral tarsal spurs basally bifurcate; basitarsi I/II/III with 7–8/9– 12/11–14 long retrosuperior macrosetae arranged in bristle-combs; ventral surface of telotarsi with dual rows of long, fine macrosetae, but dual row condition may often be confined to only basal portion on basitarsi I–III, with single file of setae in distal portion; tarsal ungues moderately long.
Measurements. See Table 7.
Variation. Coloration, morphometric and meristic variation as described above and in Figs. 157–162.
DISTRIBUTION. Known only from Jabal Samhan, Jabal Qara and Jabal Qamr, and adjacent coastal sites in Dhofar Province, Oman.
ECOLOGY. It has a preference for mesic habitats, being found in sandy wadis and rocky slopes with vegetation and moisture. Specimens taken by day were sheltering under rocks. The yellow color of the body would blend well with lighter substrates where it was collected, while the dark brown/ black posterior metasoma and telson would stand out in contrast. Similar bicolored patterns seem to have evolved independently in various other buthids (e.g. Buthacus nigroaculeatus, Centruroides bicolor, Leiurus spp., Hottentotta salei, H. saulcyi, etc.), and may be adaptive in leading visually guided vertebrate predators of scorpions away from the more vulnerable mesosoma, and towards the venom-wielding telson which can deliver mammal-specific defensive toxins. Recorded elevation range was 15–1,050 m. Scorpions that occurred together with X. xanthus were: Butheolus harrisoni sp. n., Compsobuthus acutecarinatus (Simon, 1882), Hottentotta salei (Vachon, 1980), Leiurus haenggii Lowe et al., 2014, Microbuthus kristensenorum Lowe, 2010, and Nebo whitei Vachon, 1980.
description: Published as part of Lowe, Graeme, 2018, The genera Butheolus Simon, 1882 and Xenobuthus gen. nov. (Scorpiones: Buthidae) in Oman, pp. 1-73 in Euscorpius 261 on pages 51-63, DOI: 10.18590/euscorpius.2018.vol2018.iss261.1, http://zenodo.org/record/7118814