Dibologonus, Mesibov, 2025

Dibologonus gen. nov.

Type species.

Dibologonus sladei sp. nov., by present designation.

Other assigned species.

Dibologonus major sp. nov., D. minor sp. nov., D. oedipus sp. nov.

Diagnosis.

Distinguished from other described Australian dalodesmids by the very slender gonopod telopodite split into a medial branch and a lateral solenomere with a helical prostatic groove; the two branches straight, extending distally in parallel and close together.

Description.

Males and females with body plan head + 19 rings (including telson).

Male with vertex sparsely setose, frons and clypeus setose; vertigial sulcus reaching 1 / 2 way to top of antennal sockets; sockets separated by ca 2 × socket diameter. Relative ring widths: 6> 5> 4> 3> 2> collum; ring widths 6–13 subequal, diminishing posteriorly; head approximately as wide as ring 4 or 5. Collum half-moon-shaped in dorsal view, posteriorly slightly emarginate, corner bluntly rounded. Tergite 2 without ventral pit; paranotal margin a little lower than tergite 3 margin. Midbody paranotal margin at ca 1 / 2 ring height, level. Paranotum with anterior corner rounded, laterally gently convex, posterior corner not or only slightly projecting. Midbody ring with metatergite width ca 1.3–1.4 × prozonite width; waist well-defined. Metatergite nearly smooth, with 2 transverse rows and a posterior marginal row of very small setae. Pore formula normal, ozopore near posterior corner of paranotum. Limbus a simple row of spine-like elements. Spiracles small, round, barely raised above pleurite surface, on diplosegments with posterior spiracle between leg bases. Sternites a little longer than wide, transverse impression deeper and wider than longitudinal impression, variably setose. Relative podomere lengths of midbody leg: tarsus> femur> prefemur> (postfemur, tibia); tarsus straight. Epiproct short, conical; hypoproct subtrapezoidal or broadly paraboloid; spinnerets in square array.

Gonopore small, opening distomedially on leg 2 coxa. Gonocoxae small, subconical, lightly joined distomedially. Aperture a little longer than wide, ca 1 / 2 ring 7 prozonite width, margin produced posterolaterally. Gonopod telopodites slender, straight, split into medial branch and lateral solenomere; ring 6 sternite excavate to accommodate retracted telopodites, with small tufts of setae above leg bases. Prostatic groove running from medial surface at telopodite base across posterior surface, then between medial branch and solenomere and curving in spiral around solenomere (left-handed spiral on left telopodite, right-handed spiral on right telopodite).

Name.

Greek dibolos (“ two-pointed ”) plus “ - gonus ”, an ending for genus names in Polydesmida that refers to gonopod structure. The gonopod telopodite is split into two parallel processes. Gender masculine.

Remarks.

The four species of Dibologonus gen. nov. are partly distinguishable by adult size, but more reliably by differences in the structure of the gonopod telopodite. As the telopodite processes are tightly packed together, these differences are best seen under high magnification (Fig. 9 View Figure 9 ).

Species of Dibologonus gen. nov. occur widely in eastern Victoria and southeastern New South Wales (Fig. 16 A View Figure 16 ), and more species (or significant range extensions) are likely to be found in future.