Orthomorpha similanensis, 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 : 95-97

Orthomorpha similanensis sp. n. Figs 106108

Holotype.

♂ (CUMZ), Thailand, Phang Nga Prov., Khura Buri Distr., Similan National Park, Ko Miang, Island 4, ca 40 m, 8°34'14"N, 97°38'14"E, 05.04.2010, leg. S. Panha, J. Sutcharit & N. Likhitrakarn.

Paratypes.

1 ♂, 1 ♀ (ZMUC), 1 ♂, 1 ♀ (ZMUM), 4 ♂, 3 ♀ (CUMZ), same locality, together with holotype.

Name.

To emphasize the type locality.

Diagnosis.

Differs by a strongly contrasting colour pattern, coupled with pleurosternal carinae represented by complete crests bulged anteriorly and with a sharp caudal tooth on segments 2-7, thereafter only a sharp caudal tooth on segments 8-16 (♂), or crests bulged anteriorly and with a sharp caudal tooth on segments 2-4, thereafter only a small sharp caudal tooth on segments 5-14 (♀) (see also Key below).

Description.

Length 26-30 (♂) or 31-33 mm (♀), width of midbody pro- and metazona 2.1-2.6 and 3.5-3.8 mm (♂), 2.9-3.4 and 4.0-4.3 mm (♀), respectively.

Coloration of live animals blackish, paraterga and epiproct contrastingly creamy yellow, legs and venter dark brown to blackish; coloration of alcohol material after long-term preservation dark brown to blackish, paraterga (marbled at base) and epiproct faded to pale yellow, legs and venter more pale brown (Fig. 106A-G).

Clypeolabral region densely setose, vertex sparsely so, epicranial suture distinct. Antennae moderately long (Fig. 106B), extending behind to body segment 3 (♂) or 2 (♀) dorsally. Head in width <collum <segment 3 = 4 <2 = 5-16 (♂); thereafter body gently and gradually tapering. Collum with three transverse rows of setae: 3+3 anterior, 2+2 intermediate, and 2+2 posterior; lateral corner of paraterga narrowly rounded, slightly bordered and declined ventrally, not surpassing rear tergal margin (Fig. 106A & B). Tegument smooth and shining, prozona very finely shagreened, metazona leathery, delicately rugulose, below paraterga more evidently rugulose. Postcollum metaterga with an anterior transverse row of 2+2 setae. Tergal setae long, slender, about 1/3 metatergal length. Axial line very faint, barely traceable on metaterga (♂). Paraterga very strongly developed (Fig. 106A-H), especially well so in ♂, slightly upturned and lying below dorsum (at about 1/3 of midbody height); shoulders well-developed, slightly rounded and oblique laterally; caudal corner of paraterga 2 nearly pointed, thereafter increasingly narrowly pointed towards paraterga 17-19; paraterga bent posteriad, at least slightly extending beyond rear tergal margin, more evidently so on segments 2, 3 and 17-19. Calluses delimited by a sulcus only dorsally, rather narrow, a little wider on pore-bearing segments (Fig. 106B, D & F). Posterior edge of paraterga evidently concave, more strongly so on segments 16-19 (Fig. 106F-H). Ozopores evident, lateral, lying in an ovoid groove at about 1/4 in front of caudal corner. Transverse sulcus usually broad and shallow (Fig. 106B, D & F), superficial (especially so due to coarse texture around), slightly incomplete on segments 4 and 19, complete on metaterga 5-18, slightly not reaching bases of paraterga, a little better developed in ♀ (Fig. 106B, D & F). Stricture between pro- and metazona narrow, shallow, evidently beaded at bottom down to base of paraterga (Fig. 106B, D, E & F). Pleurosternal carinae complete crests bulged anteriorly and with a sharp caudal tooth on segments 2-7, thereafter only a sharp caudal tooth on segments 8-16 (♂), or crests bulged anteriorly and with a sharp caudal tooth on segments 2-4, thereafter only a small sharp caudal tooth on segments 5-14 (♀). Epiproct (Fig. 106F-H) conical, flattened dorsoventrally, with two evident apical papillae, subtruncate at tip; pre-apical papillae evident. Hypoproct (Fig. 106G) subtriangular, caudal margin pointed; setiferous knobs at caudal edge well-separated, rather small.

Sterna delicately and sparsely setose, without modifications, but with a pair of very small, blunt, fully separated cones between ♂ coxae 4 (Figs 106I & J). A pair of conspicuous rounded tubercles flanking anterior edge of gonopod aperture, both bent posterolaterad. Legs moderately long and slender, slightly incrassate in ♂, midbody ones ca 1.3-1.4 (♂) or 0.8-0.9 times (♀) as long as body height, prefemora without modifications, ♂ tarsal brushes present until legs of segment 13.

Gonopods (Figs 107 & 108) simple. Coxa long and slender, with several strong setae distodorsally. Prefemur densely setose, about 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 tridentate tip, middle prong about as long as terminal denticle, subterminal lobule rounded, smallest; solenomere long, flagelliform, a short tip exposed.

Remark.

This new species is only known from one of the islets of Similan Archipelago, Thailand (Map 2).