Omobrachyiulus unugulis Vagalinski, 2021

Vagalinski, Boyan & Golovatch, Sergei I., 2021, The millipede tribe Brachyiulini in the Caucasus (Diplopoda, Julida, Julidae), ZooKeys 1058, pp. 1-127 : 1

Omobrachyiulus unugulis Vagalinski sp. nov.

Figs 14 , 15 , 16

Material examined

(SMNG). Holotype: ♂ (in head to ring 6, pleurotergum 7 to ring 29, and rest of body, gonopods, left antenna, right flange of pleurotergum 7, hypoproct, leg 6, a mid-body, and an end-body leg dissected), Georgia, Samegrelo-Zemo Svaneti, Mestia, source of the valley above Lengeri , 43.0742°N, 42.6983°E, 2060 m a.s.l., 27.IX.2012, F. Walther leg. Paratype: 1 subadult ♂ (in head and collum and rest of body), same collecting data as for holotype .

Diagnosis.

A species of Omobrachyiulus very similar to O. divaricatus by the general shape of the promere and by the opisthomere having a slender, rod-like, anterior process directed distad, a broad, strongly flattened, multilobed, apical outgrowth of the basoposterior process, and a similarly finely and asymmetrically bifurcate solenomere. Differs from O. divaricatus by the following gonopodal characters: promere with a more broadly rounded apex; apical outgrowth of opisthomeral basoposterior process asymmetrically bilobed, forming a dentate distal part and a thumb-like lateral part, vs. the same being more or less symmetrical, tripartite in O. divaricatus ; anterior process of opisthomere significantly lower rather than equal to, or higher than, solenomere; solenomere mostly straight, directed almost completely distad, vs. the same being abruptly bent caudad in O. divarictus ; and by the male hypoproct being tri-, rather than penta- or septidentate.

Name.

Derived from the Latin unugula meaning paw, after the apical outgrowth of the basoposterior process of the opisthomere, which resembles an animal foot with claws and a large thumb. Adjective.

Description.

Measurements: holotype ♂ in S in XI, 50+1+T, L = 29 mm, H = 1.95 mm. Paratype subadult ♂ in S X, 47+2+T.

Colouration (Fig. 14 ): Mostly brown-grey with purple tinges; head brown, with the usual pattern; collum mostly grey, dorsally brownish, with dark brown margins; prozonae grey, ventrolaterally with numerous light spots; metazonae grey, with a transverse dark brown stripe in posterior half, this abruptly narrowing below ozopore level, hind margins light brown-beige; dorsum with a black axial line; epiproct dark brown-grey, paraprocts somewhat lighter brown; legs light yellow.

External structures: Eye patches consisting of ca. 45 ommatidia arranged in easily recognisable vertical rows. Vertigial, supralabral, and labral setae: two, four, and 18, respectively. Antennae (Fig. 14A ) ca. 1.7 × as long as head in males; antennomere 2> 5 ≥ 3> 4> 6. Gnathochilarium with promentum of moderate size, separating lamellae linguales in ca. 2/5 of their length, each latter with three setae in a longitudinal row. Collum mostly smooth, with several short and shallow striae at posterolateral corners.

Body rings not vaulted. Prozonae with numerous minute grooves in posterior third. Metazonae relatively shallowly striated, n Schub = 10 or 11; setae (apparently) mostly abraded, rather short based on the few remaining. Ozopores set tightly behind pro-metazonal suture in more anterior rings, gradually moved further back, to nearly equal to their diameter behind the suture in caudalmost rings, sutures gently sinuous in front of ozopores in some rings. Tarsus of mid-body legs slightly shorter than tibia, and slightly over 3 × as long as apical claw.

Telson (Fig. 14B ): Epiproct moderately long, straight, broad, roof-like, ending with a short and blunt hyaline tip equal to, to slightly surpassed by, the longest paraproctal setae. Hypoproct (in males) (Fig. 15A ) broadly trapezoidal, tridentate, ventrally with six submarginal setae, only the teeth protruding behind rear contour of paraprocts. Paraprocts moderately densely setose, with a row of sparse short (ca. half as long as the ‘regular’ ones) and stiff setae along each caudal margin.

Male sexual characters: Mandibular stipites (in Fig. 14A ) considerably expanded, protruding mostly anteriad, forming a narrow anterior corner. Leg pair 1 compact parallel. Walking legs (Fig. 15B ) with well-developed crested pads, both tibial and postfemoral ones gradually reduced towards telson, but still visible in caudalmost pairs; femora without modifications. Pleurotergum 7 (Fig. 15C ) ventrally forming rather slender and rounded lobes originating from the zone around pro-metazonal suture, protruding mostly ventrad behind gonopods.

Gonopods (Fig. 16 ): Promere (Fig. 16B, p in Fig. 16A ) relatively slender, broadest at base, mesal margin gently concave, lateral one bulging in mid-section, both joining into a broadly rounded apex; caudal surface with a strongly pronounced and relatively long median ridge, a narrow and rather deep median groove, and a broad and deep, but indistinctly marked, distal groove; flagellum just slightly longer than height of promere. Opisthomere (Fig. 16A, C-E ) rather slender; basoposterior process shaped as a weakly pronounced, hump-like lobe, distally forming a broad, bilobed, apical outgrowth: with an apically dentate distal lobe, and a rounded thumb-like lateral lobe; anterior process well-developed, slender and rod-like, with a slightly serrate apical part; mesomeroidal lobe large, but rather weakly pronounced, flattened; mesal side with a large lobe (presumably gonocoxal gland), and a very deep anteromesal sinus; several minute spiniform filaments along flagellum channel; solenomere long and slender, significantly exceeding anterior process; apically finely and asymmetrically bifurcate, directed almost completely distad and only slightly caudad.

Female sexual characters: unknown.

Remarks.

Despite the considerable morphological similarity between Omobrachyiulus divaricatus and O. unugulis sp. nov., they undoubtedly represent two separate species, this being inferred from the few, but significant differences concerning gonopodal characters. Furthermore, the gonopod structure of O. divaricatus is remarkably consistent (in comparison with the condition in, e.g., O. caucasicus ), with almost no visible variations between specimens from all over the species’ distribution area.

General distribution.

SWGC.

The Opisthomere hortensis group

Characterisation. Promere significantly higher than opisthomere, distolaterally with a micro-squamose lobe or field; with a distinct distal groove. Opisthomere stout, compact, with a weakly to moderately pronounced mesomeroidal lobe, a basoposterior process with a moderately to well-developed proximal part, ending with a variously shaped apical outgrowth, a ridge-like anterior process of various size, being mostly fused to solenomere, a deep anteromesal sinus, a flagellum channel overgrown with very long, erect, spiniform filaments, and a simple, finger- or rod-like solenomere bent more or less caudad. Vulva with operculum shorter than bursa.

Included species.

O. hortensis (Golovatch, 1981)

O. armatus Vagalinski, sp. nov.

O. pristis Vagalinski, sp. nov.

Figures

Figure 14. Omobrachyiulus unugulis sp. nov., ♂ holotype A head and body rings 1 - 3 B telson, lateral views. Not to scale.

Figure 15. Omobrachyiulus unugulis sp. nov., ♂ holotype (SMNG) A hypoproct, ventral view B distal three podomeres of leg 6 C left flange of pleurotergum 7, ventro-lateral view. Scale bars: 0.3 mm.

Figure 16. Omobrachyiulus unugulis sp. nov., gonopods of ♂ holotype A left gonopods (without the basal parts), mesal view B right promere, caudal view C right opisthomere, oral-lateral view D distal half of the same, oral view E same, caudal view. Scale bars: 0.4 mm (C), 0.3 mm (B), 0.2 mm (A, D, E). Abbreviations: ao apical outgrowth of basoposterior process, ap anterior process, bpp basoposterior process, fc flagellum channel, ml mesomeroidal lobe, p promere, s solenomere, sf spiniform filaments.