Orthorhachis christinae, 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 : 25-26

Orthorhachis christinae n. sp.

Fig. 16; map Fig. 31

Holotype: Male. Mt Wilson , NSW, 33º30'S 150º23'E, 26 January 1979, C. Horseman. In AM, KS94913 .

Paratypes: In AM: 2 males, 1 female , details as for holotype, KS94912 ; 1 male , details as for holotype, KS 103049 (ex KS94913 ) ; 1 male, same details but Cathedral of Ferns area, 29 November 1978, field no. 1215, KS 103047; 3 males, 1 female , same details but Waterfall Picnic Area Trail, 29 November 1979, field no. 1624, KS 103050 .

Other material examined: In AM: 1 male, 1 female, Mt Keira Fauna Reserve Scout Camp , NSW, 34º24'S 150º51'E, 6 December 1978, C. Horseman, field no. 1217, KS 103048 ; 2 males, 1 stadium 7 male, same details but 25 April 1979, field no. 1564, KS18491 ; 1 male, Binnowee Drive , Blue Mountains National Park, NSW, 33º40'15"S 150º27'55"E, 580 m (GE), 15 August 1996, Australian Museum Business Services, pitfall traps, site K42 CU2, KS53430 ; 1 male, 1 female, Coates Park , Hazelbrook, NSW, 33º43'45"S 150º26'45"E, 640 m (GE), 22 August 1996, Australian Museum Business Services, pitfall traps, site M9 AU3, KS66150 ; 1 male, 1 female, Ridge Street , Woodford, NSW, 33º43'50"S 150º28'40"E, 600 m (GE), 30 September 1996, Australian Museum Business Services, pitfall traps, site M1 BU2, KS53429 ; 1 male, 2 females, Railway Parade , Hazelbrook, NSW, 33º43'55"S 150º27'00"E, 620 m (GE), 3 October 1996, Australian Museum Business Services, pitfall traps, site M4 AU4, KS66149 .

In ANIC: 1 male, Mt Keira Scout Camp, NSW, 34º24'S 150º50'E, 320 m, 5 March 1981, J. Lawrence & A. Calder, ANIC berlesate 709, leaf litter under palms, 64-000186 .

Diagnosis: Gonopod telopodite with solenomere and medial process close together at bases, the medial process terminating in three lobes, the most distal being the central one.

Description: As for the genus. Male/female approximate measurements, Mt Wilson, Mt Keira: length 16/ 17, 25/ 26 mm; midbody prozonite diameter 1.5/1.7, 2.0/ 2.2 mm; midbody width across paranota 2.1/2.2, 3.0/ 3.2 mm. Well-coloured specimens in alcohol chestnut brown with lighter paranotal corners. Antennal sockets separated by just over 2X a socket diameter. Antennae slender, relative lengths of antennomeres (2,3)>6>(4,5) in smaller specimens, 3>(2,5)>6> 4 in Mt Keira specimens. Collum D-shaped with sharp corners, about as wide as head and narrower than tergite 2. Metatergite sculpture variably distinct, Pattern A. Paranota with anterior margin convex, curving smoothly to join lateral margin without distinct corner; lateral margin parallel to long axis of body. Legs slender, leg 6 tarsus 1.7–1.8X as long as femur. Brush setae with forked tips.

Gonopod aperture ovoid but wider anteriorly, slightly wider than long, about one-third the width of the ring 7 prozonite, rim raised posterolaterally. Telopodite ( Fig. 16) short, base broad and wider than long; telopodite flattening mediolaterally distad; long setae on posterolateral surface to one-quarter telopodite height; branching beginning at between one-half and two-thirds telopodite height. Solenomere a gradually tapering cylinder with a truncated tip, curving posteriorly, then abruptly turning distally and very slightly laterally at an 'elbow'. Medial process closely pressed to solenomere at base, flattened mediolaterally, curving posteriorly and terminating just above level of solenomere 'elbow' in two tooth-like lobes, with a small toothlike projection on anterodistal edge of process at level of solenomere 'elbow'.

Female slightly larger than male, legs not swollen and unusually slender. Genital aperture with posterior margin raised in low, slightly convex curve. Cyphopods not examined.

Distribution: Known from two disjunct areas in New South Wales: the Blue Mountains west of Sydney, and Mt Keira, northwest of Wollongong ( Fig. 31). The gap is ca. 80 km.

Etymology: For the late Christine Horseman (d. 2006), collector of the holotype, a technical officer at the Australian Museum from the late 1960s to the early 1990s.

Remarks: Specimens of O. christinae from the type locality and the Blue Mountains are smaller than those from Mt Keira. The latter also have more distinct raised areas on the metatergites and proportionally longer antennae. Nevertheless, the two populations have gonopods of the same distinctive form.