Sphaerobelum nigrum, Wesener, 2019

Wesener, Thomas, 2019, First records of giant pill-millipedes from Laos (Diplopoda, Sphaerotheriida, Zephroniidae), Zootaxa 4563 (2), pp. 201-248 : 229-232

Sphaerobelum nigrum new species

Figures 6G , 20 , 21

Material examined: Type specimens: 1 M holotype (SMF) from Laos, Champasak Province, Muang Bachieng, Ban Lak 35, Tad Etu (N15°11'37.7", 106°06'06.3"E), 810 m, coffee plantation with remnant of secondary forest, leg. in vegetation, at night, by hand; 16.XI.2012; P. Jäger.

Paratype: 1 F ( SMF) from Laos, Champasak Province, Muang Bachieng, Ban Lak 35, Tad Etu (N15°11'37.7", 106°06'06.3"E), 810 m, coffee plantation with remnant of secondary forest, close to river, at rock, leg. at day, by hand, 25.XI.2009, P. Jäger & S. Bayer .

Diagnosis: S. nigrum n. sp. belongs to a group of Sphaerobelum species in which the mesal margin of the femur is modified ( Fig. 20B ). S. nigrum n. sp. shares only with S. hirsutum , S. clavigerum , S. splendidum n. sp. and S. schwendingeri n. sp. the presence of a "hook" at telopoditomere 4 of the posterior telopods( Figs 21E, F ). S. nigrum n. sp. differs from S. hirsutum in the presence of glabrous tergites, from S. clavigerum in the presence of a short locking carina on the anal shield. Differs from S. splendidum n. sp. and S. schwendingeri sp. in the presence of an axe-shaped antennomere 6, and the presence of only a short hook at the telopoditomere 4 ( Figs 21E, F ) of the posterior telopods (strongly curved telopoditomere 4 in the other two species).

Description. Based on holotype male and paratype female.

Measurements: Body length: holotype male: length ca 27.8 mm. Width, of thoracic shield = 16.1 mm, of tergite 7 = 16.8 mm (= broadest). Height, of thoracic shield = 9.8 mm, of tergite 7 = 10.1 mm (= highest). Female: length ca 34.7 mm. Width, of thoracic shield = 15.7 mm, of tergite 7 = 17.4 mm (= broadest). Height of thoracic shield = 9.3 mm, of tergite 7 = 9.8 mm (= highest). Coloration: in preserved specimens yellow with dark brown spots or black spots/bands. Head and collum black ( Fig. 6G ). Antennae and legs dark brown to black.

Head: Eyes with ca. 55 ocelli. Antennae short, with rounded joints, extending posteriorly to leg-pair 4. Lengths of antennomeres: 1=2=3=4=5<<6. All antennomeres densely pubescent, sensilla basiconica surrounding apical disc. Last antennomere thickened, apically widened, axe-shaped. Apical disc with 91/89 apical cones (male), 74/78 (female). Organ of Tömösváry located inside antennal groove. Gnathochilarium: structure typical of the order. Palpi sensory cones located in single field. Mandibles: not dissected.

Stigmatic plates: first stigmatic plate widely rounded, apex well-rounded, curved towards coxa 1 ( Fig. 20A ).

Laterotergites: laterotergite 1 and 2 elongated into a long, sharply pointed process. Collum: with glabrous surface, margins with few isolated setae. Thoracic shield: surface glabrous, but covered with small pits like tergites, setae only in grooves. Shallow grooves beset with numerous long setae, slope towards groove with 2 or 3 weak anterior and 2 or 3 posterior keels. Tergites: glabrous, but entirely covered by tiny pits. Tips of paratergites of midbody tergites projecting posteriorly ( Fig. 6G ). Endotergum: inner section without any setae or spines. Middle area with a single row of dense, round, cuticular impressions, distance between impressions slightly smaller than their diameter. Apically, 3–4 dense rows of short marginal bristles, the longest just protruding up to half of the distance to tergal margin. Bristles not smooth, but with numerous small spicules. Anal shield: well-rounded, surface completely covered by tiny setae each standing in a tiny pit. Underside with a single, black locking carina, located close to last laterotergite. Locking carinae of similar size to those of tergites. Legs: leg-pair 1 with 2 or 3 ventral spines, leg-pair 2 with 3 or 4, leg-pair 3 with 6. First two leg-pairs without an apical spine. Leg-pairs 4–21 with 9 or 10 ventral spines and one dorso-apical spine. In leg 9 femur 1.6 times, tarsus 3.7 times longer than wide ( Fig. 20B ). Femur extended mesally into a dentate margin featuring 12–14 teeth. All podomeres densely setose. Coxa with a well rounded process. Coxa process absent at first leg ( Fig. 20A ) and sharply projecting at second ( Figs 20C ; 21A ).

Female sexual characters: Vulva of gravid female large, covering mesal 1/2 of coxa, extending mesally to anterior half of prefemur ( Fig. 20C ). Operculum rounded, mesal margin projecting into a well-rounded lobe 1/3 as high as remaining operculum. Subanal plate: large, high, broadly rounded triangular. Apex deeply recessed.

Male sexual characters: gonopore covered with a single, undivided, circular, sclerotized plate ( Fig. 21A ). Anterior telopods ( Figs 21 B–D): consisting of 4 telopoditomeres above syncoxite, but telopoditomere 3 and 4 only divided by thin suture. Telopoditomere 1 slightly wider than long. Telopoditomere 2 large, as long as first, almost as long as telopoditomere 3 and 4 combined. Process of telopoditomere 2 located posteriorly, not visible in anterior view. Process of telopoditomere 2 wide, projecting to base of telopoditomere 4, apically with a wellrounded tip. Telopoditomere 3 cylindrical, straight, slightly smaller than telopoditomere 4. Telopoditomere 4 cylindrical, well-rounded, posterior side with two sclerotized spots. Telopoditomeres 1–4 in anterior view covered with long setae. In posterior view all telopoditomeres with fewer setae. Posterior telopods ( Figs 22E, F ): telopoditomere 1 rectangular, as long as wide. Immovable finger (process of telopoditomere 2) as long as movable finger, consisting of telopoditomeres 3 and 4. Immovable finger with a characteristic, distally swollen apex. Apex expanding more towards movable finger than towards mesal margin, well rounded. Apex almost twice as wide as base. Telopoditomere 3 rectangular, twice as long as wide, towards immoveable finger with a triangular expansion. Telopoditomere 4 reaching 2/3 of length of telopoditomere 3, slenderer, only weakly tapering but tip bent backwards into acute hook, very slightly curved towards immovable finger. Inner margin with two spines towards immovable finger. Telopoditomere 1 at both sides covered by setae. Telopoditomeres 2 and 3 in anterior view covered by long setae, in posterior view mainly with marginal setae. Telopoditomere 4 glabrous.

Derivatio nominis: nigrum, noun in apposition, after the, for a member of Sphaerobelum , unique black colour of the legs, head, collum, antenna and part of the tergites.

Figures

FIGURE 6. Habitus multi-layer stacked photographs of Sphaerobelum species. A: Sphaerobelum bolavensis n. sp.; B: Sphaerobelum phouloei n. sp.; C: Sphaerobelum denticulatum n. sp.; D: Sphaerobelum spinatum n. sp.; E: Sphaerobelum lachneeis n. sp.; F: Sphaerobelum peterjaegeri n. sp.; G: Sphaerobelum nigrum n. sp.; H: Sphaerobelum splendidum n. sp.; I: Sphaerobelum laoticum n. sp. Not to scale.

FIGURE 20. Sphaerobelum nigrum n. sp., holotype (SMF); A: coxa of first left leg with first stigmatic plate; B: 9th left leg; C: coxa and prefemur of second leg with vulva. Abbreviations: Cx = coxa; O = operculum of vulva; Pre = prefemur; St-Pl = stigmatic plate. Scale bars = 1 mm.

FIGURE 21. Sphaerobelum nigrum n. sp., holotype (SMF); A: coxa of second left leg with gonopore; B: right anterior telopod, anterior view; C: right anterior telopod, posterior view; D: right anterior telopod, lateral view; E: right posterior telopod, anterior view; F: left posterior telopod, posterior view. Abbreviations: Syn-Cx = syncoxite. Scale bars = 1 mm.

FIGURE 22. Sphaerobelum splendidum n. sp., holotype (SMF); A: coxa of first left leg with first stigmatic plate; B: 9th left leg; C: coxa of second left leg with gonopore; D: left anterior telopod, anterior view; E: left anterior telopod, posterior view; F: left anterior telopod, lateral view; G: right posterior telopod, anterior view; H: right posterior telopod, posterior view. Abbreviations: Cx = coxa; St-Pl = stigmatic plate; Syn-Cx = syncoxite. Scale bars = 1 mm.