Tylopus trigonum, Likhitrakarn, Natdanai, Golovatch, Sergei I. & Panha, Somsak, 2014

Likhitrakarn, Natdanai, Golovatch, Sergei I. & Panha, Somsak, 2014, Three new species of the millipede genus Tylopus Jeekel, 1968 from Thailand, with additional notes on the species described by Attems (Diplopoda, Polydesmida, Paradoxosomatidae), ZooKeys 435, pp. 63-91 : 71-74

Taxon classification Animalia Polydesmida Paradoxosomatidae

Tylopus trigonum sp. n. Figs 6, 7

Holotype.

♂ (CUMZ), Thailand, Tak Province, Umphang District, Pa Wai Waterfall, 804 m a.s.l., 16°34'29.6"N, 98°50'3.2"E, 20.01.2011, leg. C. Sutcharit & N. Likhitrakarn.

Paratypes.

1 ♂ (CUMZ), same data, together with holotype. 3 ♀ (CUMZ), same district, Thee Lor Sue Waterfall, 591 m a.s.l., 15°55'38.1"N, 98°45'12.8"E, 19.01.2011, leg. N. Likhitrakarn.

Name.

To emphasize the light brown triangle on terga; noun in apposition.

Diagnosis.

This new species shows a peculiar colour pattern, much like that observed in Tylopus schawalleri Golovatch, 2013, but differs in gonopod process h being rather short and coiled (versus high and strongly twisted), as well as by the presence of a process m (versus absent).

Description.

Length 21.2-27.8 (♂) or 22.1-24.0 mm (♀), width of midbody pro- and metazona 1.97-1.83 and 2.65-2.78 mm (♂) or 2.43-2.58 and 3.05-3.14 mm (♀), respectively.

Coloration of live animals light brown (Fig. 6A); paraterga, legs and epiproct light brown, head and collum blackish, following terga with a light brown triangle and blackish collar covering both pro- and metazonae; coloration of alcohol material after three years of preservation faded to whitish with a pattern of a contrasting dark brown inverted triangle at anterior edge of metazonae and a light brown triangle at posterior edge of prozonae (Fig. 6 B–H).

Clypeolabral region and vertex sparsely setose, epicranial suture distinct. Antennae very short (Fig. 6A, B), reaching only behind body segment 2 (♂) or collum (♀) when stretched dorsally. In width, head <segment 3 <4 <collum <segment 2 <5-17 (♂, ♀); thereafter body gently and gradually tapering. Collum with three transverse rows of strong setae: 4+4 anterior, 2+2 intermediate, and 4+4 posterior; a rounded incision laterally in posterior half; caudal corner of paraterga rounded, slightly declined ventrad, produced behind rear tergal margin (Fig. 6B, C).

Tegument rather smooth and shining, prozonae very finely shagreened, metaterga smooth and finely rugulose, leathery; surface below paraterga finely microgranulate (Fig. 6 B–H). Postcollum metaterga with two transverse rows of setae on small knobs to oblong ridges: 2+2 in anterior (pre-sulcus), 3+3 in posterior (post-sulcus) row, caudal row more strongly developed than anterior one, starting from metaterga 11 with 2+2 in anterior and 4(3)+4(3) in posterior row. Tergal setae long, strong, slender, about 1/3 of metatergal length. Axial line visible. Paraterga very strongly developed (Fig. 6 B–F, H), especially well in ♂, set high, at about 1/3 of midbody height, slightly upturned, always lying high, but below dorsum; shoulders well-developed, mostly regularly rounded and narrowly bordered, fused to callus; caudal corner narrowly rounded to fully pointed, extending increasingly beyond rear tergal margin, posterior edge clearly oblique (Fig. 6B, D, F); paraterga very thin blunt blades in lateral view, a little thicker only on pore-bearing segments. Calluses on paraterga delimited by a sulcus both dorsally and ventrally. Paraterga 2 broad, anterior edge angular, lateral edge with three evident incisions in anterior half (Fig. 6B, C). Lateral edge of following paraterga with two clear incisions, one in anterior 1/3, the other at midway, front one being particularly evident. Ozopores evident, lateral, lying in an ovoid groove at about 1/3 in front of caudal corner. Transverse sulcus usually distinct (Fig. 6B, D, H), slightly incomplete on segments 4 and 19, complete on metaterga 5-18, deep, reaching bases of paraterga, clearly ribbed at bottom. Stricture between pro- and metazonae very wide, clearly beaded at bottom down to base of paraterga (Fig. 6B, D, H). Pleurosternal carinae complete crests with a sharp caudal tooth on segment 12 (♂) or 7 (♀), thereafter increasingly well reduced in size and sharpness until segment 17 (♂) or 14 (♀), onward missing (Fig. 6C, E, H). Epiproct (Fig. 6 F–H) conical, flattened dorsoventrally, subtruncate, with two evident apical papillae directed caudally, both pointed at tip; pre-apical papillae evident, lying close to tip. Hypoproct roundly subtrapeziform (Fig. 6G), small setiferous knobs at caudal edge well-separated and evident.

Sterna very densely setose, with a small cone caudally near each coxa; a single, linguiform, deeply medially notched sternal lobe between ♂ coxae 4 (Fig. 9I, J). Legs moderately long and slender, midbody ones ca 1.1-1.2 (♂) or 1.0-1.1 times (♀) as long as body height, ♂ femora with 2-4 small adenostyles on ventral side (Fig. 7C); tarsal brushes present until ♂ leg 7.

Gonopods (Fig. 7A, B) very simple; coxa a little curved caudad, sparsely setose distoventrally. Prefemur densely setose, about 1/3 as long as femorite + “postfemoral” part. Femorite rather slender, expanded distad, slightly curved, showing a mesal groove; lobe l simple; solenophore long and slender, typically coiled, tip subtruncate; process m evident, but not spiniform; process h prominent, coiled, acute at tip.

Remark.

The ♂ paratype on metatergum 19 shows 3+3 and 6+6 setae without knobs in the anterior and posterior rows, respectively.