Pyrgodesmus obscurus Pocock 1892

Golovatch, Sergei I., 2021, Identity of the millipede genus Pyrgodesmus Pocock, 1892, the type genus of the family Pyrgodesmidae (Diplopoda, Polydesmida), Zootaxa 5068 (4), pp. 572-578 : 573-575

Pyrgodesmus obscurus Pocock 1892

Figs 1–8

Pyrgodesmus obscurus Pocock, 1892: 155 , plate 2, figs 1–1b (D).

Pyrgodesmus obscurus — Attems, 1914: 174 (R); 1936: 246 (R); 1940: 261, fig. 370 (D, R); Jeekel, 1971: 350 (R, M); De Zoysa et al., 2016: 477 (R, M); Aswathy et al., 2021: 373 (D, R).

Remark. As noted above, the original description of this species was rather superficial and incomplete, especially as regards the crucial gonopodal structure ( Pocock 1892).

Brief redescription. Body with 20 rings (19+T), length ca 10.5 mm. Coloration mostly dark grey-brown with contrasting pallid legs, tegument heavily coated with an earth crust ( Figs 4–6 ).

Head fully covered from above by a flabellate anterior brim of a dome-shaped collum, the latter with 5+5 equal, distinct, rounded lobulations at anterior margin. Antennae C-shaped, short and clavate, antennomere 5 being the largest and subequal in length to 2 nd. Paramedian tubercles/crests (PM) especially strongly developed, high, each tightly fused medially almost all along and only apically slightly divided, inclined anteriad on collum and rings 2–4, subvertical until ring 16, thereafter declined increasingly caudad ( Figs 3 & 4 ). PM mostly thickened and vaguely bilobate apically, only last few PM trilobate ( Fig. 4 ). Paraterga very low, oblique and strongly declined, vaguely bi- or trilobate at lateral margin ( Figs 3–6 ). Pore formula normal (5, 7, 9, 10, 12, 13, 15–19), ozopores borne on distinct porosteles on rings 5, 7, 9, 10, 12, 13 and 15, but opening flush on dorsal surface at base of caudal lobulation on rings 16–19 ( Figs 3–6 ). Surface below PM microgranulate, with neither DL nor i, nor Am, nor Cm discernible beneath an earth crust. PM 19 subhorizontal, fused medially and forming a deep caudal notch, tip of epiproct being slightly visible from above.

Legs robust, densely setose, each prefemur with a particularly long distoventral seta; claw small and simple ( Figs 5 & 6 ). Gonopods ( Figs 7 & 8 ) relatively simple, in situ held almost parallel to each other, with only tips of telopodites (= solenomeres), both slightly curved ventrad and poorly bifid, crossing medially; each gonopod consisting of a large, globose, densely microsetose and micropapillate coxite and a unipartite, rather long, ribbon-shaped, distally attenuating telopodite/solenomere curved caudad, strongly sunken inside a deep gonocoel and terminating the seminal groove on top.

Distribution. Pundaluoya, Sri Lanka.

Figures

FIGURES 1–8. Pyrgodesmus obscurus Pocock, 1892, male syntypes. 1. Original labels. 2. Both syntypes pierced with glass minutiae, shown relative to the length of an insect pin. 3. Habitus of a syntype, lateral view (after Pocock (1892)). 4. Picture of the same, lateral view. 5. Body rings 5–7 and gonopods in situ, ventral view. 6. Body rings 6–9 and gonopods in situ, ventrolateral view. 7 & 8. Enlarged gonopods in situ, ventral and ventrolateral views, respectively. Figs 1–3, 7 and 8 not to scale. Images courtesy Dmitry Telnov.