Orthomorpha picturata, Likhitrakarn, Natdanai, Golovatch, Sergei I. & Panha, Somsak, 2011

Likhitrakarn, Natdanai, Golovatch, Sergei I. & Panha, Somsak, 2011, Revision of the Southeast Asian millipede genus Orthomorpha Bollman, 1893, with the proposal of a new genus (Diplopoda, Polydesmida, Paradoxosomatidae), ZooKeys 131, pp. 1-161 : 17-19

Orthomorpha picturata sp. n. Figs 1112

Holotype.

♂ (CUMZ), Thailand, Phang Nga Prov., Khura Buri Distr., Similan National Park, Ko Bangu, Island 9, ca 40 m, 8°40'33"N, 97°37'08"E, 06.04.2010, leg. N. Likhitrakarn.

Paratypes.

2 ♀ (CUMZ), same locality, together with holotype.

Name.

To emphasize the picturesque appearance of the animals.

Diagnosis.

The new species differs in the small size (up to 23 mm long and 3.5 mm wide), coupled with a particular coloration and a bifid gonopod tip (see also Key below).

Description.

Length ca 19 mm (♂) and 22-23 mm (♀), width of midbody pro- and metazona 1.8 and 2.7 mm (♂), 2.3-2.5 and 3.4-3.5 mm (♀), respectively. Coloration of live animals blackish, paraterga and epiproct contrasting creamy orange, legs and venter brownish to pale brown; coloration of alcohol material after preservation faded to castaneous brown or pale brown, paraterga (marbled at base) and epiproct somewhat faded to pale pinkish or pale yellow, legs and venter paler brown (Fig. 11A-J).

Clypeolabral region densely setose, vertex sparsely setose, epicranial suture distinct. Antennae moderately long, clavate (antennomere 7 broad) (Fig. 11A & C), extending behind until body segment 3 (♂) or beyond segment 2 (♀) dorsally.

Head in width <collum <segments 3-4 <2 = 5-16 (♂, ♀); thereafter body gently and gradually tapering. Collum with three transverse rows of setae, 4+4 anterior, 2+2 intermediate, and 2+2 posterior; caudal corner of paraterga very narrowly rounded, slightly bordered and declined ventrally, not extending behind tergal margin (Fig. 11B & J). Tegument smooth and shining, prozona very finely shagreened, metazona leathery, faintly rugulose, below paraterga more evidently so. Postcollum metaterga with a transverse anterior row of 2+2 setae. Tergal setae long, slender, about 1/3 metatergal length. Axial line faint, barely traceable on metaterga. Paraterga very strongly developed (Fig. 11A-J), especially well so in ♂, slightly upturned and lying below dorsum (at about 1/3 on body height), except for paraterga 2 being subhorizontal, broad in dorsal aspect and thin in lateral view; shoulders well-developed, slightly rounded and oblique laterally; caudal tip of paraterga 2 nearly pointed, increasingly well pointed on paraterga 14-19; paraterga bent posteriad, at least slightly extending behind tergal margin, more evidently so on segments 2-3 and 14-19. Calluses delimited by a sulcus only dorsally, rather narrow, a little broader on pore-bearing segments, with 1-2 small lateral incisions in anterior 1/4 and 3/4 on callus 2 and following pore-bearing segments, but only one (at front 1/4) on following poreless segments (Fig. 11C, E, H, K & I). Posterior edge of paraterga evidently concave, more strongly so on segments 16-19 (Fig. 11F-H). Ozopores evident, lateral, lying in an ovoid groove at about 1/4 paratergal length in front of caudal corner. Transverse sulcus present on metaterga 5-18, usually narrow and shallow (Fig. 11B, D & F), superficial (especially so due to coarse texture around), slightly not reaching bases of paraterga, a little better developed in ♀ (Fig. 11I & J). Stricture between pro- and metazona broad, evidently ribbed at bottom down to base of paraterga (Fig. 11B, D, E & H). Pleurosternal carinae complete crests bulged anteriorly and with a sharp caudal tooth on segments 2-7, thereafter only a sharp caudal tooth on segments 8-18, a very small denticle on segment 19 (Fig. 11C, E & H), or crests bulged anteriorly and with a sharp caudal tooth on segments 2-4, thereafter only a small sharp caudal tooth on segments 5-16 (♀). Epiproct (Fig. 11F-H) conical, flattened dorsoventrally, with two evident apical papillae, these especially clear in ♂, slightly concave at tip; pre-apical papillae evident. Hypoproct (Fig. 11G) semi-circular, setiferous knobs at caudal edge well-separated.

Sterna delicately and sparsely setose, without modifications; a paramedian pair of small, strongly separated, setose tubercles between ♂ coxae 4. Gonopod aperture broken during removal of gonopods. Legs moderately long and slender, slightly incrassate in ♂, midbody ones ca 1.2-1.4 (♂) or 0.9-1.1 times (♀) as long as body height, prefemora without modifications, ♂ tarsal brushes present until legs of segment 8.

Gonopods (Fig. 12) simple. Coxa long and slender, with several strong setae distodorsally. Prefemoral part densely setose, less than half the length of femorite + "po stfemoral " part. The latter slender, slightly curved and not enlarged distad, with a “postfemoral” part demarcated by an oblique lateral sulcus. Solenophore with a bidentate tip, both prongs being subequal; solenomere long and flagelliform.

Remarks.

Among all nine islets of the Similan Archipelago, Thailand inspected for millipedes in April 2010, only three appeared to support Orthomorpha species, one each per islet. Only Orthomorpha picturata occurred on Ko Bangu, Island 9 (Map 2), another new species ( Orthomorpha similanensis sp. n., see below) on Ko Miang, Island 4, while Ko Huyong, Island 1 harboured still another presumed congener which regrettably cannot be described, because we only obtained female material.