Costabolus baculus, Golovatch & Vandenspiegel, 2022

Golovatch, Sergei & Vandenspiegel, Didier, 2022, Carinobolus gen. nov. and Costabolus gen. nov., two new, remarkably crested monospecific genera of spirobolidan millipedes from WestAfrica, with the proposal of a new tribe, Amblybolini tribus nova (Diplopoda, Spirobolida, Pachybolidae), Zootaxa 5150 (1), pp. 97-110 : 103-107

Costabolus baculus sp. nov.

Figs 4–7

Material examined. Holotype male (with exposed gonopods, body broken into two pieces) ( VNHM 198 ), Nigeria, 27 km NE of Calabar , 20 m inside native forest, 12.VIII.1984, collector unknown.

Paratypes: 2 males ( VNHM 198 ), same data as holotype ; 1 female ( VMNH 154 ), Nigeria, 27 km NE Calabar (Ekang road), under logs on fairly dry soil in new canopy forest farmed to young maize, 28.IV.1984, collector unknown ; 1 male, 1 female ( VMHN 199 ), Nigeria, 27 km N of Calabar , between trees, native forest, 20 m off logging road, 12.VIII.1984, collector unknown .

Name. Baculus in Latin means “crutch”, referring to the long coxal processes on male legs 2 and 3; a noun in apposition.

Diagnosis. Basically as in the genus. Body short, up to 27 mm long, with 38 body rings plus telson, metazonae with simple longitudinal crests/ribs, epiproct slightly projecting caudally. Male with tarsal pads and prominent coxal projections on leg-pairs 2 and 3.

Description. Measurements: male holotype with 39 body rings (38 + telson), ca 27 mm long, 3 mm wide. Paratypes, both male and female, same as holotype.

Coloration faded in alcohol, but a darker pattern still visible dorsally and laterally, yellowish ventrally. Head, ommatidia and anterior part of collum dark brown, antennae, legs and telson yellowish ( Fig. 4 ).

Head capsule with an axial suture, this being especially distinct on labrum; ca 22 ommatidia located in an irregular oval cluster ( Fig. 5A ).

Labrum as usual, with three irregular teeth and a single row of 12 stout marginal setae. Clypeus with two setiferous foveolae on each side ( Fig. 5E ). Incisura lateralis closed ( Fig. 5A, D ). Antennal cavity/groove present, length of antennae ca 1.3 mm; antennae shorter than body diameter. Relative lengths of antennomeres: 3=4=5<1<6<2 ( Fig. 5D ). Terminal antennomere with four large sensory cones clustered together inside a membranous area ( Fig. 5C ). Antennomeres 5 and 6 each with an apicolateral field of specialized sensilla ( Fig. 5D ).

Gnathochilarium as usual, of spirobolidan conformation. Stipites separated in basal portion, each bearing three apical setae, but no setae on ventral surface. Lamellae linguales separated by anterior portion of mentum, each with two usual setae located behind one another; mentum without a large swollen area apically between both lamellae linguales, subdivided basally by a well-marked suture ( Fig. 5H ).

Mandible: external tooth (et) prominent, inner tooth (it) with three smaller inner teeth, a thin lateral tooth (lt), six rows of pectinate lamellae (pl), molar plate (mp) with five transverse furrows ( Fig. 5F, G ).

Collum with a prominent groove along anterior margin, lateroventral margin broadly rounded, not extending ventrad as far as ventrolateral corner of body ring 2 ( Fig. 5I ).

Body rings: Metazonae heavily crested ( Fig. 5J–L ); mesozonae with longitudinal impressions, these being especially distinct ventrally ( Fig. 5K ), caudal fringe/limbus membranous, with very small and regularly spaced spinicles ( Fig. 5L ). Pre-anal ring with a small dorsal tip of epiproct overhanging the paraprocts ( Figs 4A , 5M ); hypoproct rounded; paraprocts (anal valves) well-rounded and devoid of spines or setae ( Fig. 5M ). Posterior margin of paraprocts in lateral view without distinct lips ( Fig. 5M ). Ozopores (oz) starting with body ring 6.

Legs: Midbody legs ca 1.4 mm long, with prefemur longer than coxa and as long as the other podomeres; with small tarsal pads (pa) ( Fig. 5O, P ). Male tarsi 3 up to midbody legs with a small tarsal pad not protruding past base of claw, and with a pair of setiform apical spines ( Fig. 6D ). Male leg-pairs 1, 2 and 3 modified, coxae 1 fused medially at base only, each prefemur 2 with a well-developed, unciform, basal projection (hp) ( Fig. 6B, C ), each coxa 3 with a long and spoon-shaped coxal process (cp), this being almost as long as the leg itself ( Fig. 6B, D ).

Anterior gonopods stout and relatively simple ( Fig. 6E–I ); sternite (st) produced into a wide, broadly rounded lobe, bearing clear traces of axial fusion ( Fig. 6E ); coxite (cx1) subtending much of anterior gonopods; telopodites basically 2-segmented, each consisting of a smaller, roundish, apically flattened, basal telopoditomere (t1) with a very small, accessory, subtriangular segment at base ( Fig. 6H, I ), and a much larger, lobe-shaped, distal telopoditomere (t2).

Posterior gonopods ( Fig. 6J, K , pg in H) in situ almost completely concealed inside anterior gonopods, clearly divided into a slender coxite (cx2) and a shorter telopodite (tl), both being slender ( Fig. 6J ) and connected by a tiny triangular sternite. Telopodite consisting of two components: (1) a median membranous area, and (2) a lateral sclerotized area. Sperm channel running at mesal margin of coxite through telopodite’s membranous area, ending up subapically on a rudimentary solenomere (sl) ( Fig. 6J, K ).

Paratypes. Males as holotype. Female similar in size and appearance to males, but devoid of prefemoral or coxal projections on leg-pairs 2 and 3, respectively. Vulva simple, consisting of two simple, sclerotized plates, bivalve-like and subequal in size ( Fig. 7 ). Both coxite (cxv) and operculum (o) of vulva very small and inconspicuous. Both valves only basally with one row of setae directed towards the opening. Anterior valve (av) slightly larger than posterior one (pv) ( Fig. 7 ).

Figures

FIGURE 4. Costabolus baculus sp. nov., male holotype (VNHM 198). A & B. Habitus, lateral and ventral views, respectively. Scale bars: 5 mm.

FIGURE 5. Costabolus baculus sp. nov., male paratype (VNHM 198). A & B. Head, lateral and frontal views, respectively. C. Tip of antenna. D. Left antenna, lateral view. E. Clypeus, frontolateral view. F & G. Mandible, ventral and mesal views, respectively. H. Gnathochilarium, ventral view. I. Right lateral margin of collum, lateral view. J. A midbody metazona. K. Ozopore. L. Limbus of a midbody ring. M. Posterior part of body, ventral view. N & O. Midbody legs, ventral and lateral views, respectively. P. Tarsus of a midbody leg, lateral view. Abbreviations: et, external tooth; it, internal teeth; lt, lateral tooth; mp, molar plate oz, ozopore; pa, tarsal pad; pl, pectinate lamella. Scale bars: 500 µm (A, B), 100 µm (D, E, F, G), 50 µm (C, P), 200 µm (L, H, J, K, N, O), 10 µm (L).

FIGURE 6. Costabolus baculus sp. nov., male paratype (VNHM 198). A. Anterior part of body, ventral view. B. Coxal projections on leg-pairs 2 and 3. C. Leg-pair 2, posterior view. D. Leg-pair 3, posterior view. E-I. Everted gonopod block, anterior, ventrolateral, ventral, posterior and posterolateral views, respectively. J. Right posterior gonopod, lateral view. K. Drawing of left posterior gonopod, caudal view. Abbreviations: 1, median membranous area of telopodite; 2, lateral sclerotized area of telopodite; cx1, coxite of anterior gonopod; cx2, coxite of posterior gonopod; pg, posterior gonopod; hp, basal projection of prefemur 2; st, sternite; sl, solenomere; t1 and t2, telopoditomeres 1 and 2 of anterior gonopod; tl, telopodite of posterior gonopod. Scale bars: 500 µm (A, C), 100 µm (B), 200 µm (D, E–K).

FIGURE 7. Costabolus baculus sp. nov., female paratype (VMNH 154). A. Ventral view of both vulvae, B. Left vulva, lateral view. Abbreviations: av, anterior valve; cx, coxite of leg 1; cxv, coxite of vulva; o, operculum; pv, posterior valve. Scale bars: 500 µm (A), 200 µm (B).