Nagaxytes Srisonchai, Enghoff & Panha
Ruttapon Srisonchai, Henrik Enghoff, Natdanai Likhitrakarn & Somsak Panha, 2018, A revision of dragon millipedes II: the new genus Nagaxytes gen. nov., with the description of three new species (Diplopoda, Polydesmida, Paradoxosomatidae), European Journal of Taxonomy 462, pp. 1-44: 4-11
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|Nagaxytes Srisonchai, Enghoff & Panha|
Genus Nagaxytes Srisonchai, Enghoff & Panha gen. nov.
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The genus Nagaxytes gen. nov. is characterized by:
1. Paraterga subspiniform.
2. Metaterga with 2 rows of tubercles/cones/spines (lateral spines of posterior row very long).
3. Male femora 5 and 6 without modification.
4. Postfemoral part of gonopod conspicuous, demarcated from femur by a deep mesal sulcus and a shallow/deep lateral sulcus.
5. Lamina lateralis obviously separated from lamina medialis.
6. Lamina medialis long and curved, apically fringed/hooked.
‘ Naga ’ is a Sanskrit and Pali word, relating to a category of snake-like spirits in Buddhist and Hindu mythology, and refers to the snake-like shape of the lamina medialis of the gonopod; ‘- xytes ’ ensures harmony with Desmoxytes (and its synonym Pteroxytes Jeekel, 1980 ).
Included species (4)
- N. acantherpestes ( Golovatch & Enghoff, 1994) gen. et comb. nov.
- N. erecta Srisonchai, Enghoff & Panha gen. et sp. nov.
- N. gracilis Srisonchai, Enghoff & Panha gen. et sp. nov.
- N. spatula Srisonchai, Enghoff & Panha gen. et sp. nov.
Srisonchai et al. (2018) proposed to subdivide Desmoxytes sensu Golovatch & Enghoff (1994) into five genera. The ‘ acantherpestes ’ group (= Nagaxytes ) is well-defined by several distinct morphological characters (see diagnosis), especially the distinctive subspiniform paraterga and the very long lamina medialis of the gonopods. Even though the subspiniform paraterga are relatively similar to those of the ‘ gigas ’ group, the gonopod details are very different.
General description of Nagaxytes gen. nov.
The description applies to adult males and females, except for the gonopods or when ‘male’ is specified ( Figs 1–3View Fig. 1View Fig. 2View Fig. 3). The general description of gonopods is based mainly on Nagaxytes gracilis gen. et sp. nov. ( Figs 4–5View Fig. 4View Fig. 5).
SIZE. Body length 22–34 mm (male) 24–38 mm (female), width ca. 2.0– 2.4 mm (male) 2.8–3.4 mm (female), varies between species, usually female wider and longer than male.
COLOUR ( Figs 1View Fig. 1, 11–12View Fig. 11View Fig. 12, 17View Fig. 17, 22View Fig. 22). Specimens in life with brown or reddish brown colour or pinkish brown (possibly aposematic colouration). Colour in alcohol: all specimens partly faded to pale whitish brown after one year’s preservation in alcohol; specimens kept in darkness faded more slowly.
ANTENNAE ( Fig. 2 A – B, DView Fig. 2). Long and slender, covered by delicate setation, usually reaching backwards to body ring 5–7 (male) and 4–6 (female) when stretched dorsally. Antennomere 3 = 4> 5 ≥ 2> 6> 1> 7> 8.
HEAD. Delicately setose; vertex, labrum and genae delicately setose; epicranial suture conspicuous as brown stripe.
COLLUM ( Fig. 3 A, CView Fig. 3). With three transverse rows of setae/tubercles and spines; 3+3 setae/tubercles (anterior row), 1+1 setae/tubercles (intermediate row) and 2+2 spines (posterior row); lateral spines of posterior row very long. Paraterga of collum wing-like, usually elevated at ca. 25°–40°, with two conspicuous notches at lateral margin.
TEGUMENT ( Fig. 3 A – GView Fig. 3). Often dull, sometimes quite shiny; collum, metaterga (except anterior part of metaterga smooth) and surface below paraterga finely microgranulate; prozona finely shagreened; paraterga, sterna and epiproct smooth. Stricture between prozona and metazona wide, usually quite shallow, sometimes quite deep.
METATERGA ( Figs 2 AView Fig. 2, 3 A, D, GView Fig. 3). With one or two transverse rows of setae/tubercles and spines; usually with 2+2 setae/tubercles/cones/spines in anterior row and 2+2 spines in posterior row (sometimes setae/ tubercles/cones/spines in anterior row poorly developed or absent); lateral spines of posterior row longer and larger than mesal ones. Suture (transverse sulcus) on metaterga quite deep, conspicuous on body ring 5–17 in all species. Mid-dorsal (axial) line missing.
PLEUROSTERNAL CARINAE ( Fig. 3 BView Fig. 3). Forming a complete crest on ring 2, smalls ridges on ring 3 and/or 4, missing on remaining body rings.
PARATERGA ( Fig. 3 A –B, D –E, G –HView Fig. 3). Subspiniform, long, elevated at ca. 50°–70° (male) or 45°–70° (female), directed caudolaterad on rings 2–17 or 2–18, directed increasingly caudad on ring 19 or 18–19. Callus and shoulder poorly developed. Anterior margin with two distinct notches; on body rings 9, 10, 12, 13, 15–18 a denticle usually present at lateral margin near tip (denticle absent in some rings). Degree of elevation of paraterga in male usually higher than in female. Posterior edge concave; posterior angle pointed and sharp. Ozopore visible in lateral and dorsal views, round, small, somewhat inconspicuous.
TELSON ( Fig. 3F –G, L, NView Fig. 3). Epiproct quite short, often flattened dorsoventrally, tip usually subtruncate, sometimes emarginate; lateral setiferous tubercles conspicuous, digitiform; apical tubercles mostly conspicuous, sometimes inconspicuous; setiferous tubercles beyond lateral setiferous tubercles long, digitiform; epiproct apically with four spinnerets at the corners of a square, not in a depression, anterior pair close to apical tubercles ( Fig. 3LView Fig. 3). Paraprocts convex. Hypoproct subtriangular or subtrapeziform; caudal margin often subtriangular, sometimes round, with two conspicuous or inconspicuous setiferous tubercles.
STERNA ( Figs 2CView Fig. 2, 3KView Fig. 3). Sparsely setose; cross-impressions somewhat deep, sometimes quite shallow. Sternal lobe between male coxae 4 modified; usually subtrapeziform, sometimes incompletely bilobed, varying between species; tip slightly emarginate, sometimes deeply emarginate or even incompletely bilobed; with two pores seen in posterior view.
LEGS ( Fig. 2A – CView Fig. 2). Very long and slender. Relative lengths of podomeres: femur> tarsus> tibia> prefemur = postfemur> coxa> claw. Male femora 5 and 6 without modification in all species.
GONOPODS ( Figs 4–5View Fig. 4View Fig. 5). Coxa longer than prefemoral part, with a distoanterior group of setae. Cannula long or short. Telopodite straight. Prefemoral part usually shorter than femur, sometimes subequal in length to femur. Femur usually long, sometimes quite short. Seminal groove running entirely on mesal surface of femur. Mesal sulcus and lateral sulcus conspicuous. Postfemoral part conspicuous, shorter than femur. Solenophore well-developed: lamina lateralis variously modified; swollen, sometimes long digitiform/lamella-like and projecting, sometimes with spatula-like lobe: lamina medialis longer than lamina lateralis, snake-like, tip curving down. Solenomere relatively long.
Distribution and habitat
This genus is known only from the western part of Thailand: Prachuap Khiri Khan Province (Hua Hin and Kui Buri Districts), Kanchanaburi Province (Sai Yok and Thong Pha Phum Districts) and Tak Province (Mae Sot and Umphang Districts) ( Fig. 27View Fig. 27). All four species seem to be local endemics, highly restricted to limestone habitats, and all have narrow distribution ranges. The specimens were usually found on humid rocks, rock walls, leaf litter or surface roots of trees. Some species can be found syntopically in the same habitat with other dragon millipede species.
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