Tasmanocambala, Mesibov, Robert, 2018

Mesibov, Robert, 2018, Cambaloid millipedes of Tasmania, Australia, with remarks on family-level classification and descriptions of two new genera and four new species (Diplopoda, Spirostreptida), ZooKeys 827, pp. 1-17 : 1

Tasmanocambala gen. n.

Type species.

Tasmanocambala greeni sp. n., by present designation.

Name.

“Tasmano”, combining form of Tasmania + Cambala , type genus of Cambalidae ; feminine gender.

Diagnosis.

Differs from the other seven Southern Hemisphere cambalid genera by the anterior gonopod telopodite ending in a thin tab just anterior to an apical, transverse comb of setae; from Dimerogonus and Eumastigogonus in having a smoothly rounded apex of the coxal process, without a medial extension; from Proscelomerion in lacking a pseudoflagellum and in having a rounded rather than acuminate tip on the coxal process; from Apocoptogonus and Euryischiogonus by the flagellum not having a bifurcate tip; from Stenischiogonus by the lack of a distinct medial lobe on the tip of the anterior gonopod telopodite; and from Zinagon by the male leg 1 femur being much wider than the more distal three podomeres and by the anterior section of the posterior gonopod lacking a needle-like extension.

Description.

Living animals grey-black, in life with lighter-coloured annular band at rear of metazonite. Male/female midbody diameters to ca 2.5/2.9 mm; trunk ring counts to 55/56.

Head smooth apart from sparse setae on clypeus. Antenna reaching ring 2 dorsally when extended, relative antennomere lengths (3,6)>(2,4,5), 6th antennomere widest, 4 apical cones. Ocelli of older individuals in 3 or 4 rows, posterior row longest with 7+ ocelli. Collum half-moon-shaped in dorsal view; corners broadly rounded. Gnathochilarium (Fig. 1A) with gnathochilarial stipetes well separated posteriorly by wide mentum; a broad medial depression in the mentum, deepest posteriorly, with anteriorly concave posterior margin; promentum triangular with base of triangle convex. Trunk rings (Fig. 2A-C) smooth, shiny; prozonite demarcated from metazonite by shallow constriction containing suture dorsally; suture turning posteriorly just ventral to ozopore, becoming dorsalmost of parallel series of horizontal striae on lateral and ventral portions of metazonite; limbus short, lamellar. Ozopores beginning on ring 6 at ca 1/2 ring height, slightly higher on subsequent rings; ozopores very small, round, in small, slight depressions at slightly less than 1/2 the distance between suture and posterior metazonite margin. Telson with dorsal margin of preanal ring only slightly produced, not forming distinct epiproct; hypoproct margin broadly paraboloid. Midbody legs ca 1/2 ring diameter in length; relative podomere lengths (prefemur=tarsus)>femur>postfemur>tibia; claw ca 1/2 as long as tarsus.

Male leg 1 (Fig. 1B) on undivided sternite; coxae fused with sternite but demarcation clearly visible; coxa mediolaterally widened and anteroposteriorly flattened, a few long setae in 1 or2 transverse rows on distolateral margin of coxa; prefemur very short, wide, subcylindrical; femur wide, tapering distally, extended basally on anterior surface as bluntly rounded process overlapping both prefemur and coxa; postfemur and tibia subcylindrical; tarsus subcylindrical and tapering distally, with deep, narrow groove medially (Fig. 1C); claw absent (or in some specimens small, malformed, on one leg of a pair); a few very small setae on distalmost 4 podomeres; relative widths prefemur> femur >> postfemur> tibia> tarsus; relative lengths (femur = tarsus)> postfemur> tibia> prefemur.

Aperture on ring 7 (Fig. 2D-F) cordate (apex to rear), the lateral margins slightly raised. Anterior and posterior gonopods forming small, compact structure, tilted posteriorly in ring 7. Coxa of anterior gonopod (Figs 1D, E; 2) about as long as telopodite or a little shorter, anteroposteriorly flattened and with large posterior concavity holding telopodite; apex rounded and very thin, directed distomedially; flagellum not bifurcate, arising medially on coxal base and curving first posterobasally, then distally, then anteriorly. Telopodite of anterior gonopod (Fig. 1D, E) not as wide as coxa, tapering distally, posterolaterally slightly excavate with a few very short setae in deepest portion of excavation near base ("rudimentary terminal podomere" of Korsós and Read (2012)); telopodite ending in translucent, rounded tab with comb of setae just posterior to tab, the setae shorter than tab. Posterior gonopods (Fig. 1F) reaching ca 2/3 height of anterior gonopods; anteriorly divided by deep, oblique groove into anterolateral and posteromedial sections, subequal in height; anterolateral section tapering at ca 1/2 section height from wide base to apically rounded lamina; posteromedial section with apex stout, bluntly rounded and tipped with sparse brush of short setae, and with row of very short setae along anteromedial margin of section.

Females like males in overall appearance but noticeably stouter; vulvae not examined.

Distribution.

So far known only from Tasmania, Australia.

Remarks.

Males of Tasmanocambala gen. n. species are identifiable by examination of the tip of the anterior gonopod, even with the gonopods lying in situ in ring 7: there is a terminal fringe of setae apparent behind a thin, translucent, anterior tab. The type species is likely to be a species complex (see Remarks on the type species) and the taxonomy of this genus would greatly benefit from genetic analysis.

The deep medial groove on the male leg 1 tarsus (Fig. 1C) is hard to detect with optical microscopy. It may be an autapomorphy for the genus, or it may be present in other cambaloid millipedes but overlooked by describers.