Gephyrodesmus Jeekel, 1983

Mesibov, Robert, 2008, The millipede genera Gephyrodesmus Jeekel, 1983 and Orthorhachis Jeekel, 1985 in southeastern Australia, a new Lissodesmus Chamberlin, 1920 from Victoria, and observations on male leg setae, spinnerets and metatergite sculpture (Diplopoda: Polydesmida: Dalodesmidae), Zootaxa 1790, pp. 1-52 : 11-12

Gephyrodesmus Jeekel, 1983

Gephyrodesmus Jeekel, 1983:145 ; 1985:50. Shelley et al., 2000:102.

Type species: G. cineraceus Jeekel, 1983 by original designation.

Diagnosis: H+20 Dalodesmidae with tarsus up to 1.5–1.7X as long as femur, forked tips on brush setae, dorsal spinnerets not enclosed and gonopod telopodite divided into two large branches: a lateral solenomere bent or curving posteriorly and turning abruptly distally at a distinct 'elbow', and a medial process curving posteriorly and not reaching as far distally as the solenomere tip. Distinguished from Tasmanodesmus by the presence in the latter of a third telopodite process lateral to the solenomere and by the presence in Gephyrodesmus of discrete raised areas on the metatergites. Distinguished from Orthorhachis by the branching into solenomere and medial process beginning at more than half the telopodite height in Orthorhachis , and at onethird or less the telopodite height in Gephyrodesmus .

Description: Head with frons and vertex moderately setose, vertex less so. Antenna slender, relative antennomere lengths (2,3)>6>(4,5), antennomere 6 widest. Tergite widths increasing gradually from rings 2– 5, about equal from 5–17; tergites 3, 4 shorter than 2 and 5; posterior paranotal corners produced beginning tergite 2. Waist without prominent longitudinal striations; limbus composed of long, narrow, flat tabs with irregularly toothed ends. Metatergites and paranota with low, discrete, raised areas in Pattern A (see metatergite sculpture section, above), most bearing a small seta in posterior half. Paranota with slightly convex anterior edge and variably well-defined anterior 'shoulder' with slightly upturned, partly roughened margin; lateral margin more or less straight and parallel to body, dipping anteriorly in lateral view, with 3–5 small notches, each with a minute seta on anterior corner of notch; posterior paranotal corners produced as broad, bluntly rounded projections, flat in lateral view, the projections increasing gradually in length from anterior to posterior; posterior margin minutely and irregularly serrate. Spiracles small, openings slightly elliptical, only slightly raised above pleural surface; on diplosegments with anterior spiracle just anterior of coxal midline above a small projecting shelf of cuticle, posterior spiracle about midway between leg-bases. Pore formula 5, 7, 9, 10, 12, 13, 15–19; ozopore opening dorsolaterally close to paranotal margin and just lateral to raised areas, near posterior corner at three-quarters the length of paranotum. Sternites variably setose, slightly longer than wide or as long as wide, transverse impression deeper than longitudinal. Legs ( Fig. 5B) slender; prefemur swollen dorsally, femur slightly so, swelling greatest on anterior legs; tarsus long, thin, slightly curved, up to 1.5–1.7X as long as femur; relative podomere lengths tarsus>>femur>prefemur>>(postfemur, tibia). Numerous sphaerotrichomes on tarsus and tibia of anterior legs, hemispherical with sharp-pointed, tapered setal shaft inclined distally and slightly outwards; at least some brush setae on basal podomeres with obviously forked tips ( Fig. 1D). Preanal ring sparsely setose; hypoproct paraboloid; epiproct bluntly rounded, extending well past anal valves; dorsal spinnerets set on dorsal rim of low-walled cavity containing ventral spinnerets ( Fig. 3C). Male with small gonopore opening ventrally on swelling of leg 2 coxa, not on prominent raised cone. Gonocoxae setose distally on anterolateral and posteromedial surfaces, somewhat concave medially, weakly joined anteromedially. Cannula prominent, inserting anteromedially on telopodite. Telopodites short, when retracted extending to leg 6 coxae; leg 7 coxae well separated, leg 6 coxae slightly separated. Prostatic groove running laterodistally on anterior surface of telopodite base before curving distally and following solenomere to tip.

Distribution: Forest in higher-rainfall areas of southeastern Australia, from central Victoria to eastern central New South Wales ( Fig. 12).

There is a ca. 300 km gap between known localities for the two New South Wales species of Gephyrodesmus . However, southeastern New South Wales has not yet been well surveyed for dalodesmids, and the gap may be a sampling artifact. Northeastern New South Wales and far southeastern Queensland, on the other hand, have been reasonably well collected without yielding specimens of a Gephyrodesmus species , and Coolah Tops (ca. 31º40'S), the type locality for one of the new species described below, may be at or close to the northern range limit for the genus. In central Victoria, it is not yet known whether Gephyrodesmus occurs west of the Kilmore Gap, which separates the main, eastern mass of the Great Dividing Range from the smaller, scattered outliers of the Range to the west.

Remarks: The four known Gephyrodesmus species are very similar in size and general appearance, and differ chiefly in gonopod details and in the relative prominence of raised areas on the metatergites. In his genus description, Jeekel (1983, p. 146) refers to 'Pleural keels weakly developed in a few anterior somites', but I could not confirm this observation in G. cineraceus or in the other three Gephyrodesmus species ; the pleural areas of the first rings are smoothly convex in anterior or posterior view.