Tasmaniosoma decussatum, Mesibov, 2010

Mesibov, Robert, 2010, The millipede genus Tasmaniosoma Verhoeff, 1936 (Diplopoda, Polydesmida, Dalodesmidae) from Tasmania, Australia, with descriptions of 18 new species, ZooKeys 41 (4), pp. 31-80 : 56-58

Tasmaniosoma decussatum sp. n.

urn:lsid:zoobank.org:act:28ECADB3-5E75-4A06-B6D2-61D431FF7E53

Figs 4D , 14; map Fig. 25

Holotype. Male, Australia, Tasmania, Rattler Hill , 41°13'43"S 147°53'20"E ( EQ 744353) ± 100 m, 650 m, 27 August 1990, R. Mesibov, plot NE2, QVM 23 :51555.

Paratypes. 2 males, 3 females, Pearly Brook , Tas, 41°04'18"S 147°39'43"E ( EQ 555529) ± 100 m, 80 m, 1 March 1992, R. Mesibov, QVM 23 :46692 ; 2 males, details as for holotype, QVM 23 :46703 ; 2 males, same details but 3 September 1990, QVM 23 :46704 ; 1 male, Rattler Hill , Tas, 41°13'49"S 147°53'21"E ( EQ 744351) ± 100 m, 680 m, 23 August 1990, R. Mesibov, plot NE1, QVM 23 :46700 ; 2 males, same details but 25 August 1990, QVM 23 :46701 ; 1 male, same details but 26 August 1990, QVM 23 :46702 ; 4 males, E of Rattler Hill, Tas, 41°13'43"S 147°53'16"E ( EQ 743353) ± 100 m, 650 m, 18 January 2005, R. Mesibov, QVM 23 :46699 .

Other material examined. 86 males from 13 other localities (see Appendix)

Diagnosis. Metatergites with three weakly developed, transverse rows of low tubercles, gonopod telopodite apex divided into cluster of five processes including broad, flattened solenomere, the most lateral process curving medially.

Description. Male/female approximate measurements: length 11/ 11 mm, ring 12 paranota width 1.3/ 1.3 mm. Live colour not known; in alcohol, decoloured with small reddish patches dorsally.

Most non-gonopod details as for T. armatum , but antennomere 3 longest, relative widths tergite 6>5>(4,head)>2>3>collum, ring 12 paranota 1.3 × as wide as prozonite, leg 6 femur longer than prefemur, male midbody metatergites 1.8 × as wide as long. Three transverse rows of ca 10 large, low tubercules on tergites sometimes just detectable in lateral view with oblique lighting, not as clearly expressed as in co-occurring T. clarksonorum sp. n. Ring 2 pit ( Fig. 4D ) deep, very wide, with rim well-defined except posteriorly. Ring 6 sternite with legs 6 not as widely separated as legs 7; no leg 6 tab;

Figure |4. Tasmaniosoma decussatum sp. n., paratype male ex QVM 23:46699. A Posterior view of gonopods in situ B posterior and slightly lateral view of left gonopod telopodite. Setation not shown in B, dashed line marks course of prostatic groove. Scale bars = 0.2 mm. A small portion of the background in A has been digitally edited for clarity.

leg 7 tab short with brush of fine setae; anterior margin of sternite with groups of fine setae laterally, not in dense brushes.

Gonopod telopodite (Fig. 14) straight, stout, slightly tapered distally; base extended posteriorly as concave shelf (concave upwards); posteromedial surface roundly ridged longitudinally. Telopodite divided at ca 3/4 telopodite height into tight cluster of five processes: (a) solenomere anteroposteriorly flattened, produced as small round- ed tab directed medially and larger distal tab with rounded edge and small medial tooth, prostatic groove opening centrally on distal edge; (b) short, slender, acute process arising anteromedial to solenomere origin and slightly bent medially; (c) laminate process closely applied to distal tab of solenomere on anterolateral side and slightly longer than solenomere; (d) and (e), two long, blade-like processes arising anterior to laminate process, the lateral process acute and curving slightly posteromedially, the medial process strongly tapered and curved posteromedially, the tip turning distally. Small group of short, fine setae at ca 1/2 telopodite height on lateral surface of posterior ridge; sparse, fine setae running anterodistally from basal shelf; and a few fine setae in row on lateral surface at ca 1/2 telopodite height. Prostatic groove running distally, then curving laterally to enter base of distal tab of solenomere, and curving within tab (concave medially).

Female with posterior margin of epigynum produced as short, wide trapezoid.

Distribution. Often locally abundant in wet eucalypt forest and cool temperate rainforest over ca 1500 km 2 in the eastern portion of northeast Tasmania, from 80 to at least 740 m elevation ( Fig. 25 ). Co-occurs with T. clarksonorum sp. n. at Mt Michael and Mt Victoria and near Weldborough in the northeast highlands. Sympatric with T. cacofonix sp. n., but co-occurrences may be rare because the latter species prefers drier, more open forest. Possibly parapatric with T. gerdiorivum sp. n. in the western part of the T. decussatum range.

Etymology. Latin decussatus, “X-shaped”, adjective, for the usually crossed tips of two of the gonopod processes in situ.

Figures

Figure 4. Male ring 2, ventral view of right side (anterior to right) showing variation in structure. A Tasmaniosoma compitale sp. n., paratype male QVM 23:45970, pit not apparent B T. armatum Verhoeff, 1936, topotypical male ex QVM 23:46567, pit fairly shallow, not well defined medially and posteriorly C T. cacofonix sp. n., voucher male ex QVM 23:46724, pit deep, small D T. decussatum sp. n., male paratype ex QVM 23:46699, pit deep, large. Scale bars = 0.2 mm.

Figure 25. A Localities as of 31 January 2010 for Tasmaniosoma barbatulum sp. n. (squares), T. clarksonorum sp. n. (crosses), T. decussatum sp. n. (open circles) and T. fragile sp. n. (triangles). See also Figs 23 and 26. Scale bar = 50 km. B Map of Tasmania showing location of main map (rectangle).