Dasystigma margaretae ( Jeekel, 1984 ) Mesibov, 2003

Mesibov, Robert, 2003, A new genus of Tasmanian millipedes (Diplopoda: Polydesmida: Dalodesmidae) with unusual spiracles and a mosaic distribution, Memoirs of Museum Victoria 60 (2), pp. 197-206 : 203-204

Dasystigma margaretae ( Jeekel, 1984) comb. nov.

Figures 1, 3C, 3D, 4, 5C, 5D, 10, 11, 14 (map)

Lissodesmus margaretae Jeekel, 1984: 99 .

Material examined. Holotype and paratypes. Australia, Tasmania. “Lake Augusta, 25.IV.1979 [on cushion plant] 25 April 1979, Tasmanian Department of Agriculture 19A17, holotype, 6, 1 + O (fragm.), 2 juv. O + (19 somites), 1 juv. O + (18 somites) paratypes ” ( Jeekel, 1984: 99). When I inspected the type-containing vial in 2001, I found two cotton-plugged genitalia tubes and (under a cotton pad) a number of body fragments. The genitalia tubes contained the male holotype and the fragmented mature female paratype, respectively, both in good condition. After removing a paratype male segment 7 for SEM examination, I placed the remaining body fragments in a small cotton-plugged glass tube. The three tubes and all accompanying labels were then sealed in an alcohol-filled McCartney vial for continuing storage at the New Town Laboratories of the Tasmanian Department of Primary Industries, Water and Environment (formerly the Department of Agriculture ) .

Other material. 97 males, 66 females and 72 juveniles from 52 unique localities including Alberts Marsh, Anglers Creek , Blackman R., Blue Tier Creek , Boyer, Brumbys Creek , Butlers Gorge, Coal Marsh, Coles Creek , Dromedary Creek , Fingal Tier, Flexmore Creek , Florentine R., Gulf Creek , Halls Creek , Lake Dobson , Liawenee, Little Florentine R., Lookout Hill, Lost Falls , Meehan Range, Mossy Marsh Creek , Mt Mismanagement , Native Tier, Old Mans Head, Pinnacles Creek , R. Dee, Rocka Rivulet, Sassafras Hill, St Pauls Dome, Tarraleah, Tiger Creek , Tooms Lake, Tooms White Gum Reserve and Yangena Hill .

Diagnosis. Differs from D. bonhami in having a broader, more flexed and more prominently toothed femoral process; from D. huonense and D. tyleri in having the posterior spiracle on diplosegments located above the anterior leg; from D. tyleri in having much “hairier” spiracles, spiracles also being larger than those in D. tyleri (or in other dalodesmids).

Description. As for the genus except in the following details. Both spiracles on diplosegments ( Fig. 5C) positioned over anterior leg, hair-like structures emergent from spiracles and apparent at low magnification, spiracles unusually large for a dalodesmid. Paranotal margin slightly convex; posterior corner variably projected ( Figs 3C, D; see Remarks). Gonopod telopodite ( Figs 10, 11) with prefemoral process bent mesad, sharply narrowing distad, apex curving caudad, apical edge slightly serrulate, a single tooth on mesal edge of process at about three-quarters of process length. Femoral process curving caudad and mesad and terminating just proximal to level of tooth on mesal edge of prefemoral process. Femoral process massive, divided into a broadly cuneate anterior portion and a posterior spike; distal and posterior margin of cuneate portion with numerous heavy teeth, spike crossing below cuneate portion in manner of a thumb bent slightly towards palm.

Distribution and macrohabitat. Common in dry and wet eucalypt forest and in subalpine woodland over c. 12 000 km 2 in eastern and central Tasmania ( Fig. 14), from the south side of the Fingal Valley south to the north side of the Little Swanport R. valley, and from near the east coast west to the Little Florentine R.; so far known at altitudes c. 100–1100 m elevation. Locally abundant in places in the Eastern Tiers, on the eastern fringe of the Central Plateau and in wet forests in the Derwent valley.

Remarks. Jeekel (1984) gave a complete description of this species from the type locality, Lake Augusta on Tasmania’s Central Plateau; for the sake of consistency I have included my own summary. This taxon is the most variable within Dasystigma . The prefemoral process is straighter and narrower in the eastern portion of the range ( Fig. 10A) than in the west ( Fig. 10B) and the femoral process less bent mesad. A distinctive variant, here called the “Derwent form,” is restricted to the valley of the Derwent R. ( Fig. 14), where it replaces more typical D. margaretae . In the “Derwent form” the spiracles are somewhat less “hairy” ( Fig. 5D) and the prefemoral process somewhat broader ( Figs 10C, 11). The most striking difference, however, is in the form of the paranota: the margins have moved ventrad relative to those in typical Dasystigma and the posterior corners are very strongly projected caudad and laterad ( Fig. 3D). In future, genetic data may justify the erection of a new species for this geographically and morphologically distinctive variant. I am reluctant at this time to name the “Derwent form” formally, as it differs less from more typical D. margaretae in gonopod details than do the three forms recognised here as new species.