♂ (CUMZ), Thailand, Chanthaburi Prov., Khlung Distr., Troknong Waterfall, 12°54'29"N, 102°24'12"E, 01.10.2009, leg. C. Sutcharit & N. Likhitrakarn.

25 ♂, 30 ♀ (CUMZ), 3 ♂, 3 ♀ (ZMUC), 3 ♂, 3 ♀ (ZMUM), same data, together with holotype.

To emphasize this species being not quite typical to readily fit into any of the former species groups.

Superficially, this new species strongly resembles Orthomorpha communis sp. n., especially as regards the color pattern, the degree of development of some paraterga, and size. Yet the two species differ markedly in the development in Orthomorpha atypica sp. n. of distinct sternal cones between ♂ coxae 4, coupled with a peculiar denticle placed on top of the outer lobule of the solenophore, not between the two terminal lobules characteristic of other species (see also Key below).

Length 32–39.5 (♂) or 34.5–44 mm (♀), width of midbody pro- and metazona 3.0–3.6 and 5.0–5.6 mm (♂), 3.6–4.0 and 5.5–6.4 mm (♀), respectively.

Coloration of live animals (Fig. 28A) blackish-brown with contrasting creamy light orange paraterga and epiproct, posterior halves of metaterga light yellow-brown to light brown, antennae blackish, legs dark brown; coloration of alcohol material after preservation (Fig. 25B-J) uniformly dark brown with contrasting pallid paraterga, epiproct and tip of antennae, legs brown to light grey-brown, posterior halves of metaterga light brown to brown.

Clypeolabral region densely setose, vertex barely setose, epicranial suture distinct. Antennae moderately long (Fig. 28A), clavate (antennomere 6 broadest), extending behind body segment 3 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 3+3 posterior; posterior quarter evidently rugulose, mid-dorsal part with a superficial and shortened axial line; paraterga slightly declined ventrally, discontinuing dorsum’s convexity, subrectangular, nearly reaching caudal edge; caudal corner of paraterga very narrowly rounded (Fig. 28B). Tegument of metaterga shining, leathery, rugulose-tuberculate, especially well so on several anterior metaterga; prozona very finely shagreened, metazona below paraterga faintly rugulose, finely microgranulate only near coxae. Metaterga 2–5 with two rows of 2+2 anterior and 3(4)+3(4) setiferous cones, usually slightly smaller cones in anterior (pre-sulcus) row and more evident ones laterally in posterior row (Fig. 28B & C); thereafter same pattern, but traceable only as insertion points, tuberculation gradually growing obliterate to become nearly wanting on a few caudalmost metaterga. Metatergum 19 with 3+3 anterior and 4+4 posterior setae, the latter also borne on minute knobs or oblong wrinkles. Tergal setae very short, simple, about 1/5 metatergal length. Axial line barely traceable only on metaterga, slightly better visible in anterior halves than in posterior ones, always incomplete and sometimes missing. Paraterga very strongly developed (Fig. 28B-H), especially well so in ♂, all lying below dorsum (at about 1/3 body height), mostly subhorizontal (sometimes slightly upturned only on segments 2 and 3 in ♂ or only on segment 2 in ♀), in lateral view modestly enlarged on pore-bearing segments, thinner on poreless ones; shoulders always present, rather regularly rounded and narrowly bordered, fused to callus; caudal corner of all paraterga pointed, beak-like, extending increasingly beyond rear tergal margin, slightly curved mesad on segments 18 and 19 (Fig. 28F). Calluses delimited by a sulcus both dorsally and, albeit considerably more poorly so, ventrally, segment 2 with three very faint incisions at lateral edge, two similarly faint incisions on following poreless segments, one much stronger incision in front of pore sinuosity on pore-bearing segments. Posterior edge of paraterga evidently concave, especially strongly so on segments 16–19. Ozopores evident, lateral, lying in an ovoid groove at about 1/4 in front of caudal corner. Transverse sulcus evident (Fig. 28B-F & H), thin, deep and only slightly incomplete on metaterga 2–4, complete, at most very faintly beaded at bottom, reaching bases of paraterga on metaterga 5–18, barely visible, highly superficial and again incomplete on metatergum 19 in ♂; somewhat less strongly developed in ♀. Stricture between pro- and metazona narrow and rather shallow, evidently beaded at bottom down to base of paraterga. Pleurosternal carinae complete high crests with a sharp caudal tooth on segments 2–4(5), thereafter increasingly well divided into a front bulge and a caudal tooth, both increasingly strongly reduced in size, bulge until segment 14, tooth until segment 17 (♂), or carinae considerably lower, their caudal tooth strongly rounded and only barely traceable until segment 17 (♀). Epiproct (Fig. 28F-H) conical, flattened dorsoventrally, very faintly narrowed caudad, with two evident apical papillae directed caudally, subtruncate at tip; pre-apical papillae very small, lying close to tip. Hypoproct (Fig. 28G) semi-circular, caudal margin rounded, setiferous knobs at caudal edge medium-sized and well-separated.

Sterna sparsely setose, without modifications; cross-impressions shallow, especially so due to a superficial axial impression; a large, setose, transverse lobe bearing a paramedian pair of large, basally contiguous cones between ♂ coxae 4 (Fig. 28I & J). A paramedian pair of small, but evident tubercles in front of gonopod aperture. Legs moderately long and slender, slightly incrassate in ♂, midbody ones ca 1.2–1.3 (♂) or 0.8–1.0 times (♀) as long as body height, prefemora without modifications, ♂ tarsal brushes present only on legs 1–5(6).

Gonopods (Figs 29, 30) simple. Coxa long and slender, with several strong setae distodorsally. Prefemur densely setose, less than half the length of femorite + “postfemoral” part. Femorite slender, slightly curved and nearly not enlarged distad, with a “postfemoral” part demarcated by an oblique lateral sulcus. Solenophore with a bidentate tip, both prongs being subequal, but terminal lobule with an unusual minute denticle near base; solenomere long and flagelliform.