Tetracentrosternus theelorsuensis, Likhitrakarn, Natdanai, Golovatch, Sergei I. & Panha, Somsak, 2013

Likhitrakarn, Natdanai, Golovatch, Sergei I. & Panha, Somsak, 2013, The millipede genus Tetracentrosternus Pocock, 1895 (Polydesmida, Paradoxosomatidae, Alogolykinae, Alogolykini), with a description of the first, new species from Thailand, ZooKeys 358, pp. 1-10 : 3-7

Tetracentrosternus theelorsuensis sp. n. Figs 1-3

Holotype

♂ (CUMZ), Thailand, Tak Province, Umphang District, Thee Lor Sue Waterfall, 590 m a.s.l., 15°55'38"N, 98°45'13"E (converted from GPS data), 19.01.2011, leg. N. Likhitrakarn.

Paratypes.

♂ (CUMZ), same District, Mokro Subdistrict, roadside, 1,168 m a.s.l., 16°14'14"N, 98°59'23"E, 20.01.2011, leg. N. Likhitrakarn. 5 ♀, 1 juv. (CUMZ), same District, Pa Wai Waterfall, 804 m a.s.l., 16°34'30"N, 98°50'3"E, 20.01.2011, leg. S. Panha, C. Sutcharit & N. Likhitrakarn.

Name.

After Thee Lor Sue Waterfall, the type locality, which is the largest and highest waterfall in Thailand.

Diagnosis.

Differs from congeners mainly by the first pair of ♂ legs lacking femoral adenostyles, coupled with unmodified sterna and the distal half of the gonopod telopodite being strongly curved, elongate and distally carrying three evident processes. See also Remarks above and Key below.

Description.

Length 21-23.5 (♂) or 19.5-22.5 mm (♀), width of midbody pro- and metazona 1.92-1.98 and 2.54-2.75 mm (♂) or 2.07-2.35 and 2.77-3.12 mm (♀), respectively.

Coloration of live animals dark brown (Fig. 1A); paraterga, legs and epiproct light brown, head, collum and metazona 2-4 blackish, following terga with a blackish triangle covering both pro- and metazona; coloration of alcohol material after 2 years of preservation faded to whitish or yellow with a pattern of a contrasting dark brown triangle at posterior edge of pro- and metazona, castaneous brown below paraterga; head and antennomeres 6 and 7 brown to castaneous brown; venter and a few basal podomeres light brown to yellow-brown, legs growing infuscate (brown) distally; tip of antenna pallid (Fig. 1 A–H).

Clypeolabral region and vertex sparsely setose, epicranial suture distinct. Antennae moderately long (Fig. 1A, B), reaching body segment 4 (♂) or 3 (♀) when stretched dorsally. In width, head <collum <segment 3 = 4 <2 <5-16 (♂, ♀), thereafter body gently and gradually tapering. Collum with three transverse rows of setae: 5+5 in anterior, 3+3 in intermediate and 4+4 in posterior row; a very faint incision laterally in posterior 1/3; caudal corner of paraterga rounded, slightly declined ventrad, not extending behind rear tergal margin (Fig. 1B, D). Tegument smooth and shining, prozona very finely shagreened, metaterga smooth and delicately rugulose, leathery; surface below paraterga finely microgranulate. Postcollum metaterga with two transverse rows of setae: 2+2 in anterior and 3+3 in posterior row, traceable at least as insertion points when setae broken off. Tergal setae long, strong and slender, about 1/3 of metatergal length. Axial line visible, barely traceable on proterga (♂). Paraterga strongly developed (Fig. 1 A–H), especially so in ♂, mostly slightly upturned, lying high (at about upper third of midbody height); caudal corner nearly or fully pointed; either clearly (♂) or only very slightly extending beyond rear tergal margin (♀); paraterga very thin in lateral view, like blunt blades, a little thicker only on pore-bearing segments. Calluses on paraterga 2 delimited by a sulcus both dorsally and ventrally, on following paraterga only dorsally, rather broad on pore-bearing segments. Paraterga 2 broad, anterior edge angular, a little better so in ♀, lateral edge with two small, but evident incisions in anterior half; posterior edge clearly concave (Fig. 1B, D). Anterior edge of paraterga 3-9 clearly convex, of paraterga 10-18 nearly straight and slightly bordered. Lateral edge of paraterga with a slight, but evident incision in anterior 1/3. Posterior edge of paraterga clearly concave, especially strongly so in segments 16-19 (Fig. 1 A–D). Ozopores evident, lateral, lying in an ovoid groove at about 1/4 in front of caudal corner. Transverse sulcus usually distinct (Fig. 1C, D, F), slightly incomplete on segments 4, 18 and 19, complete on metaterga 5-17, deep, not reaching bases of paraterga, at most faintly beaded at bottom, a little better developed in ♀. Stricture between pro- and metazona wide, evidently ribbed at bottom down to base of paraterga (Fig. 1 B–D, F–H). Pleurosternal carinae complete crests with a sharp caudal tooth in segment 2, a small, caudal, mostly sharp tooth until segment 7 (♂) or 6 (♀) (Fig. 1B, G, H). Epiproct (Fig. 1F, H) conical, flattened dorsoventrally, with two small apical papillae; tip subtruncate; pre-apical papillae small, but visible, lying not too close to tip. Hypoproct roundly subtriangular, setiferous knobs at caudal edge well-separated and evident.

Sterna moderately setose, without modifications; a linguiform, sternal lobe between ♂ coxae 4 (Fig. 1I, J). Adenostyles absent on femur 1 (Fig. 3A). A paramedian pair of evident tubercles in front of gonopod aperture. Legs moderately long and slender, slightly incrassate in ♂, midbody ones ca 1.2-1.3 (♂) or 0.8-1.1 times (♀) as long as midbody height, prefemora without modifications, ♂ tarsal brushes present in all legs.

Gonopods (Figs 2, 3B, C) complex. Coxa a little curved, short, subcylindrical, rather densely setose distoventrally. Prefemur densely setose, length less than 1/4 of femorite + “postfemoral” part. Femorite as usual, very short, delimited distally by a ridge (R). Femoral process (fp) a slender, distally deeply bipartite flagellum, with branch fp2 somewhat longer than fp1. Acropodite (= solenophore) elongate, clearly unciform, in proximal 1/3 with a small, but distinct, mesal, apically denticulate process (Z), in distal 1/4 with a similar, but lateral and more strongly dentate process (Y), as well as a spine (X) at its base. Solenomere (sl) branching off level to fp, very long, flagelliform, mostly sheathed by a slightly longer solenophore.