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

publication ID

http://doi.org/ 10.3897/zookeys.41.420

publication LSID




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scientific name

Tasmaniosoma decussatum

sp. n.

Tasmaniosoma decussatum   sp. n.


Figs 4D View Figure 4 , 14; map Fig. 25 View Figure 25

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

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

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 View Figure 4 ) 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 View Figure 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.


Departamento de Geologia, Universidad de Chile