Malayorthomorpha halabala, Likhitrakarn & Golovatch & Sittichaya, 2022

Likhitrakarn, Natdanai, Golovatch, Sergei I. & Sittichaya, Wisut, 2022, Review of the millipede genus Malayorthomorpha Mrsic, 1996 (Diplopoda, Polydesmida, Paradoxosomatidae), with descriptions of two new species from Thailand and a key to its species, ZooKeys 1118, pp. 1-19 : 1

publication ID	https://dx.doi.org/10.3897/zookeys.1118.89593
publication LSID	lsid:zoobank.org:pub:B1B42B9E-1CCA-4E85-A22E-39710CFA755E
persistent identifier	https://treatment.plazi.org/id/3FB913EC-E071-4A1A-A306-9657A857AFDB
taxon LSID	lsid:zoobank.org:act:3FB913EC-E071-4A1A-A306-9657A857AFDB
treatment provided by	ZooKeys by Pensoft
scientific name	Malayorthomorpha halabala
status	sp. nov.

Treatment

Malayorthomorpha halabala View in CoL sp. nov.

Figs 2A View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5

Material examined.

Holotype: Thailand - Yala Province • ♂; Betong District , hill in evergreen forest, on forest floor; 1440 m a.s.l.; 5°55'N, 101°26'E; 22 May 2021; Wisut Sittichaya leg.; CUMZ GoogleMaps . Paratype: Thailand - Yala Province • ♀; same District, elfin montane forest ( Malaya Phytochorion province ); 1430 m a.s.l.; 25 May 2022; Wisut Sittichaya leg.; CUMZ .

Diagnosis.

This new species seems to be particularly similar to M. siveci Mršić, 1996, with which it shares most of the gonopodal characters. It differs from M. siveci by the wider body, 2.7-3.2 mm (vs smaller, 1.2 mm), the colour pattern which is uniformly red brown with lighter red brown paraterga (Fig. 3A-F View Figure 3 ) (vs a light brown body with the collum and caudal edges of metazonae margined darker brown; Fig. 1A View Figure 1 ), as well as the pleurosternal carinae present until segment 11 (vs until segment 5), the sternal lobe between ♂ coxae 4 with a pair of small cones laterally near base (Fig. 3E, H, I View Figure 3 ) (vs absent, Fig. 1D View Figure 1 ), and the tip of the gonopod with a denticulate margin (Figs 4A, B View Figure 4 , 5C, D View Figure 5 ) (vs smooth and rounded; Fig. 1E-G View Figure 1 ).

Description.

Length 29.3 (♂) or 36.2 mm (♀), width of midbody pro- and metazonae 2.1 and 2.7 mm (♂) or 2.7 and 3.2 mm (♀), respectively.

Colouration of live animal rusty red (Fig. 2A View Figure 2 ), edges of paraterga light red brown; antennae dark brownish, legs and venter contrasting light yellow (Fig. 2A View Figure 2 ); colouration in alcohol, after one week of preservation, red brown (Fig. 3A-F View Figure 3 ); edges of paraterga light red brown, head and antennae brown, legs, venter and a few basal antennomeres contrasting light yellow (Fig. 3A-G View Figure 3 ).

Clypeolabral region sparsely setose; epicranial suture distinct. Antennae long, extending caudally past metaterga 5 (♂) or metaterga 3 (♀) when stretched dorsally. In width, segment 3 <4 = collum <segment 2 = head <segment 5 <6-17, body gently and gradually tapering thereafter.

Collum with three transverse rows of setae: 4+4 in anterior, 2+2 in intermediate, and 3+3 in posterior row, all mostly abraded, but still traceable as insertion points; lateral incisions absent; caudal corner of paraterga very broadly rounded, declined ventrad, produced slightly past rear tergal margin (Fig. 3A, B View Figure 3 ).

Tegument generally smooth and shining, prozonae finely shagreened, metaterga finely leathery and faintly rugulose (Fig. 3A, C, F View Figure 3 ), surface below paraterga leathery and rugose (Fig. 3B, D, E View Figure 3 ). Postcollum metaterga with two transverse rows of setae traceable at least as insertion points when setae broken off: 2+2 in anterior (presulcus) and 3+3 in posterior (post-sulcus) row. Tergal setae simple, slender, ca. 1/3 as long as metaterga. Axial line barely traceable both on pro- and metazonae.

Paraterga rather well developed (Fig. 3A, C, F View Figure 3 ), lying rather high (at upper 1/3 of body), slightly upturned, but lying below dorsum; anterior edge broadly rounded and narrowly bordered, fused to callus; lateral edge without incisions; caudal corner very narrowly rounded, not produced past rear tergal margin except in rings 2 and 3 (Fig. 3A, B View Figure 3 ); posterior edge nearly straight. Paraterga 2 broad, anterior edge angular and rounded, lateral edge without incisions (Fig. 3A View Figure 3 ).

Calluses on paraterga rather narrow, delimited by a sulcus fully on dorsal side and in about posterior 2/3 on ventral side; on poreless rings more narrow than on pore-bearing ones in dorsal view (Fig. 3B, D, E View Figure 3 ). Ozopores evident, lateral, lying in an ovoid groove at about 1/3 in front of posterior edge of metaterga.

Transverse sulcus usually distinct (Fig. 3A, C, F View Figure 3 ), complete on metaterga 5-17, narrow, line-shaped, rather deep, not reaching the bases of paraterga, very faintly ribbed at bottom, incomplete and nearly wanting on segment 18. Stricture between pro- and metazona wide, deep, ribbed at bottom down to base of paraterga starting with segment 5 (Fig. 3A-E, F View Figure 3 ). Pleurosternal carinae complete crests with a sharp caudal tooth on rings 2-4, increasingly reduced and retaining a sharp caudal tooth on rings 5 and 6 thereafter, further retained as a small caudal tooth and increasingly reduced until segment 11, absent from segment 12 on (♂, ♀) (Fig. 3B, D, E View Figure 3 ).

Epiproct (Fig. 3E-G View Figure 3 ) conical, flattened dorsoventrally, with two evident, but small, rounded, apical papillae; tip subtruncate; pre-apical papillae small, but evident, lying close to tip. Paraprocts regularly convex, each with premarginal sulci medially and two pairs of setigerous knobs at medial margin (Fig. 3G View Figure 3 ). Hypoproct roundly subtrapeziform, setigerous knobs at caudal edge very small and well-separated (Fig. 3G View Figure 3 ).

Sterna sparsely setose, shining, cross-impressions shallow, without modifications; a single, linguiform, medially rather deeply notched sternal lobe between ♂ coxae 4, with a pair of small cones laterally near base (Fig. 3E, H, I View Figure 3 ). A conspicuous and high ridge present in front of gonopod aperture. Legs long and slender (Fig. 3B View Figure 3 ), midbody ones ca. 1.4-1.6 (♂) or 1.2-1.3 (♀) times as long as body height, without modifications, ♂ tarsal brushes absent.

Gonopods (Figs 4A-D View Figure 4 , 5 View Figure 5 ) simple; coxa a little curved caudad, densely setose distoventrally. Prefemur as usual, densely setose, about 1/3 as long as femorite + postfemoral part. Femorite rather stout, wider than prefemur or postfemur, slightly expanded distad, suberect, showing a distinct mesal groove/hollow (g), with a sulcus demarcating a postfemoral part; seminal groove running entirely mesally along fermorite, solenomere (sl) flagelliform, almost fully sheathed by solenophore (sph). Lamina medialis (lm) well developed, short and unciform, terminal lobe sheathing the tip of solenomerite. Lamina lateralis (ll) elevated, prominent, stout, expanded apically, denticulate at caudal edge (Figs 3A, B View Figure 3 , 4C, D View Figure 4 ).

Etymology.

To emphasize Hala-Bala Wildlife Sanctuary, the type locality. Noun in apposition.

Remarks.

A comparison of these two species shows only a few differences, but they are sufficient to distinguish both. The type locality of M. siveci , Park Belum, is located quite far away (ca. 50 km) from this new place. In addition, because the elevations between the two localities are greater than 1000 meters above sea-level, it seems improbable that the species is one and the same. Consequently, we conclude that the two are obviously distinct species.

The specimens were collected in a primary sub-elfin montane forest with no significant disturbance due to human activity, in a high mountainous area of southernmost Thailand (Fig. 2B, C View Figure 2 ). The area is dominated by a single plant species, Dacrydium elatum . The canopy of Dacrydium elatum is low (ca. 10-15 m above ground), flat and continuously covering the area. The understorey is dense and covered with dwarf branches of small hardwood trees and teeming with bryophytes, lichens, orchids and ferns. The forest floor is with abundant orchids, ferns, liverworts, and thick slowly degraded bio-litters. The female specimen was easy to spot on the substrate and observed crawling on the leaf litter surface (Fig. 1A View Figure 1 ).