Unixenus carnarvonensis Short & Huynh

Short, Megan & Huynh, Cuong, 2013, Four new species of Unixenus Jones, 1944 (Diplopoda, Penicillata, Polyxenida) from Australia, ZooKeys 278, pp. 75-90 : 77-79

Unixenus carnarvonensis Short & Huynh sp. n. Fig. 1 A–K

Holotype.

Female, Meedo Station, WA, site MO3, 25°39'13"S, 114°37'37"E, wet pitfall traps 22 August– 11 October 1994, collected by P. West et al., WAM T71123. Specimen mounted on slide, deposited in WAM.

Paratypes.

One male and 2 females, slightly damaged, Woodleigh Station, WA, site WO5, 26°11'45"S, 114°25'23"E, wet pitfall traps 22 August– 10 October 1994, collected by M. Harvey et al., WAM T71120 (male), T127782 and T127783 (females). One female, same collection as holotype, WAM T127781. All paratypes mounted on slides, deposited in WAM.

Etymology.

For Carnarvon region, the type locality; adjective. All specimens of this species identified to date were collected as part of the Carnarvon Survey carried out by WAM and the Department of Conservation and Land Management (now part of Department of Environment and Conservation).

Diagnosis. Antennal article VI with 3 basiconic sensilla, 1 coeloconic sensillum, no associated setiform sensillum; seta present on tarsus 1 of legs 2-13, elongate smooth sided setiform setae on leg segments, ornamental trichomes b with large insertion points.

Description.

Measurements: Body length 2.8-3.3 mm with no differences between sexes, caudal bundle 0.3 mm.

No freshly collected specimens available. Specimens had been preserved in 70% ethanol. Body yellow brown in colour, trichomes largely missing.

Head with 8 ocelli each side: 4 dorsal, 4 lateral (1 anterior, 2 medial and 1 posterior). Vertex with anterior rows of trichomes arranged as typical for the genus Unixenus , with a gap to two posterior groups of trichomes arranged in 2 closely positioned straight oblique rows. Number of trichomes in posterior rows of vertex of head each side varies from 10-13 (anterior), 5-9 (posterior). Trichobothria equal in size, arranged in shape of isosceles triangle with greater width a–c (Fig. 1A).

The antennae with proportions of 8 articles and 4 sensitive cones typical of the genus. Article VI with 3 thick basiconic sensilla of equal length, coeloconic sensillum posterior to basiconic sensilla (Fig. 1C). Antennal segment VII typical of the genus with 1 coeloconic sensillum to the posterior followed anteriorly by 2 thick basiconic sensilla of similar height; 1 setiform sensillum between the basiconic sensilla (Fig. 1B). Clypeo-labrum with 10 setae along posterior margin; anterior margin of labrum with 5-6 rounded lamellar teeth each side of median cleft; surface covered with tiny spherical papillae, papillae reducing in size to the posterior margin and lacking tiny hairs (Fig. 1D). Gnathochilarium typical of the genus with lateral palp 2.5 × length of medial palp; lateral palp with 13-15 cylindrical sensilla, medial palp with 22 sensilla.

Collum with arrangement of trichomes on tergites similar to Unixenus mjoebergi , with symmetrical pattern of trichomes each side of a broad median gap, with anterior and poste rior rows merging laterally to form rosettes of trichomes, and further trichomes scattered between these rows. Small lateral protuberances each with row of 4-6 forward facing trichomes (Fig. 1E). Tergites 2-9 with trichomes arranged on posterior half of the tergite with one distinct posterior row with a medial gap and ending with small clusters later ally. Further trichomes anterior to this row loosely arranged in two to three rows (Fig. 1E). Anterior trichomes directed towards head while remaining trichomes directed posteriorly. Tergite 10 with 2 rows of trichomes arranged along posterior edge with broad medial gap (Fig. 1E). Conical pleural projections along each side associated with tergites 2-10, each with a dense cluster of trichomes. Tergal trichomes barbate, same structure as Unixenus mjoebergi .

Legs 1 and 2 without trochanter, leg 1 also lacks tarsus 1. Trochanters legs 3-13 lack setae. Chaetotaxy as follows: coxa 1, 1 seta, coxa 2, 2 setae, coxae 3-13, 2-3 setae; prefemur, postfemur, tarsus 2, legs 1-13 and tarsus 1, legs 2-13, with 1 seta; femur 1, 1 seta, femur 2, 1-2 setae, femur 3-13, 2-3 setae (Fig. 1F), setae distinctive elongate setiform (Fig. 1G) with distal seta of femur longer, small setae on postfemur, tibia, tarsus 1 and tarsus 2 (Fig. 1H); telotarsus bearing slender anterior spinous projection longer than the claw which bears anterior process, presence of posterior process unable to be determined, lamella process present (Fig. 1I). Male coxal glands not visible due to damage.

Telson with ornamental trichome insertions arranged almost symmetrically with 6-10 trichomes a, 1b, and 3c each side of the midline (holotype has 4 trichomes c on right side). Large insertion points for trichomes b (Fig. 1J). A small indentation external to trichomes c, either side. Single caudal bundle typical of genus. Hooked caudal trichomes with 2-5 hooks on barbed stems, majority with distal facing barbs only along stem proximal to hooks (Fig. 1K), some with distal and proximal facing barbs.

Distribution.

So far known only from two sites in the Carnarvon region of Western Australia (Fig. 5). Co-occurs with Unixenus mjoebergi .

Remarks. This species is very similar to Unixenus mjoebergi and cannot be separated without examination under high magnification.