Orthorhachis durabilis, Mesibov, 2008

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 : 26-28

Orthorhachis durabilis n. sp.

Figs. 5D, 7A, 17; map Fig. 31

Holotype: 1 male, Rutherford Creek , Brown Mountain near Nimmitabel, NSW, ca. 820 m, 26 May 1970, R. W. Taylor & R. Bartell, rainforest, ANIC berlesates 285-6. In ANIC, 64-000189.

Paratypes: In ANIC : 1 male, Rutherford Creek , Brown Mountain, NSW, 9 January 1968, M. Upton, rainforest, leafmould, ANIC berlesate 55, 64-000187; 3 males, 1 female, Monga , NSW, 35º35'S 149º55'E, 27 February 1968, M. Upton & L. Mound, rainforest, ANIC berlesate 72, 64-000188; 1 male, details as for holotype but ANIC berlesate 287, 64-000190.

In MV: 2 males, Cobbanah Creek , Vic, 37º38'12"S 147º14'09"E, 320 m, 25 November 2004, R . Mesibov & T . Moule , K-10662, 10663 ; 4 females, same details, K-10664–10667; 2 males, 3 females, 1 stadium 7 female, Uralla Nature Reserve , Trafalgar, Vic, 38º13'55"S 146º08'40"E, 200 m, 2 August 2005, R . Mesibov , K-10673–10678 ; 1 male, 1 female in copula, Buldah Gap Road , S of Buldah, Vic, 37º18'25"S 149º09'57"E, 560 m (GE), 10 November 2006, R . Mesibov & T . Moule , K-10682, 10683 ; 1 male, 1 female, same details, K- 10684, 10685.

Other material examined: In AM: 1 male , Emerald district , Vic, August 1904, collector 'E.N.J.', KS 103051; 1 male, 1 female , ca. 15 km SE of Countegany, near Two River Plain , Wadbilliga Trail National Park, NSW, 36º17'50"S 149º32'32"E, 970 m, 17 May 2006, C.A. Car, KS 103052 .

In MV: 5 males, 1 female, near Trafalgar , Vic, August 1890, W. Kershaw, K-10655 ; 2 males, Thorpdale , Vic, 1 April 1899, collector unknown, K-10656 ; 1 male, 2 females, 1 stadium 7 male, National Park , Vic, 11 June 1932, collector unknown, K-10657 ; 2 males, 1 female, 1 stadium 7 male, Wombargo Creek , Rockbank , Black Mountain, Vic, 30 April 1947, C. Barrett, K-10658 ; 1 male, 1 female, 3.8 miles E of turnoff on Benambra-Suggan Buggan Road , Vic, grid 1553(3) map ref 618434, no date or collector, snow gum stand, under logs, K-10659 ; 3 males, 1 female, 2.3 miles from Suggan-Buggan Road , Vic, grid 1553(3) map ref 618438, no date or collector, snow gum stand, grass ground cover, under logs, K-10660 ; 1 male, 1 female, grid 1553(3) map ref 616440, Vic, no date or collector, snow gum stand, K-10661; 1 male, Slippery Hill near Dargo, Vic, 37º23'05"S 147º12'54"E, 920 m, same date and collectors, K-10668 ; 1 male, 1 stadium 7 male, Mt Buller , Vic, near sewage plant, 37º08'56"S 146º27'27"E, 1560 m, 1 January 2005, K. Bonham, K-10669 ; 1 male, 2 females, ' Loch Springs' property, Trafalagar, Vic, 38º13'38"S 146º08'55"E, 150 m, same date and collector, K- 10671 ; 1 male, 1 female, Uralla Nature Reserve , Trafalgar, Vic, 38º13'36"S 146º08'53"E, 140 m, 19 April 2005, R . Mesibov , K-10670 ; 1 male, 1 stadium 7 male, Darlimurla , Vic, 38º21'58"S 146º11'05"E, 200 m, 1 August 2005, N. Porch & R . Mesibov , K-10672 ; 1 female, Sunny Creek at Yarragon South, Vic, 38º14'54"S 146º05'31"E, 350 m, 3 August 2005, R . Mesibov & J. Poppins, K-10679 ; 1 male, Trafalgar East , Vic, 38º12'54"S 146º12'32"E, 190 m, 4 August 2005, R . Mesibov , K-10680; 1 stadium 7 male, Yarragon South , Vic, 38º15'06"S 146º06'23"E, 340 m, 21 April 2006, R . Mesibov , K-10681 ; 1 male, 1 female, Nadgee State Forest , S of Eden, NSW, 37º17'42"S 149º49'21"E, 100 m (GE), 12 November 2006, C. & G. Car, R . Mesibov & T . Moule , K-10686 ; 1 male, 1 female, Board Road , Mt Disappointment State Forest, Vic, 37º25'37"S 145º08'50"E, 770 m (GE), 20 September 2007, R . Mesibov , K-10687 .

In WAM: 1 male, 1 stadium 6 female, 'The Beeches', Vic, 37º28'S 145º49'E, 25 March 1991, M.S. Harvey & M.E. Blosfelds, T 73068 .

Diagnosis: Paranota very wide (midbody paranota width twice as great as ring width), metatergites with Pattern B sculpture. Gonopod telopodite with solenomere and medial process well separated, the latter expanded distally and terminating in a wide truncation, with the anterior corner produced as a small distal tooth.

Description: As for the genus. Male/female approximate measurements: length 18/ 20 mm, midbody prozonite diameter 1.5/ 1.8 mm, midbody width across paranota 3.0/ 3.2 mm. Colouring variable in alcohol, ranging from near-uniform grey-brown to medium brown with paler mottling. Antennal sockets separated by 1.5X a socket diameter. Antennae short, stouter than in other Orthorhachis , relative lengths of antennomeres (2,6)>3>(4,5). Collum D-shaped with posterior margin slightly emarginate on either side, slightly wider than head and narrower than tergite 2. Metatergite sculpture very distinct, Pattern B ( Fig. 7A). Paranota very wide,anterior margin sloping posterolaterally to distinct corner, lateral margin more or less parallel to long axis of body; ozopore between one-half and two-thirds the length of the lateral margin ( Fig. 7A). Legs short, leg 6 tarsus 1.2X as long as femur ( Fig. 5D). Brush setae with forked tips.

Gonopod aperture ovoid, wider than long, about one-third the width of the ring 7 prozonite, rim raised posterolaterally. Telopodite ( Fig. 17) short, broad at base, tapering distally; long setae on posterolateral surface to one-third telopodite height; branching beginning at two-thirds telopodite height. Solenomere a slightly tapering rod with a bluntly pointed tip, directed distally and slightly posteriorly, slightly S-shaped in lateral view (right gonopod). Medial process well-separated from solenomere, broader than solenomere at base, expanding distally and mediolaterally flattened, ending at half solenomere height in a wide truncation with a posterior corner which extends further posteriorly than solenomere in lateral view, and with a small distal tooth at anterior end of truncation.

Female slightly larger than male, legs not swollen. Genital aperture with posterior margin raised in slightly convex curve, bent slightly anteriorly. Cyphopods not examined.

Distribution: From near sea level to at least 1560 m over ca. 60000 km 2 in eastern Victoria and far southeastern New South Wales ( Fig. 31). I have collected O. durabilis under loose bark on logs, in leaf litter and under pieces of rotting wood on the ground.

Etymology: Latin durabilis , lasting, adjective, for the persistence of this species in farmed landscapes in the West Gippsland district of Victoria.

Remarks: Ignoring gonopod structure, this species would not readily be recognised as an Orthorhachis : the tarsi are short and the paranota are remarkably wide and narrow. The gonopods, however, conform to the Orthorhachis pattern and are similar to those of O. tallagandensis and O. weiri , which have long tarsi and more typically shaped and sized paranota.

O. durabilis varies little over its remarkably large range: specimens from Monga and Mt Disappointment State Forest, ca. 450 km apart, are virtually identical. On the gonopod telopodite, there is minor variation in the depth of the branching and in the degree of overall taper.

This species is unusual among southeastern Australian dalodesmids for its apparent tolerance of habitat disturbance. In Victoria, I have found it in degraded bush remnants, on roadsides and on the margins of pasture adjoining forest.