Desmoxytes Chamberlin, 1923

Srisonchai, Ruttapon, Enghoff, Henrik, Likhitrakarn, Natdanai & Panha, Somsak, 2018, A revision of dragon millipedes I: genus Desmoxytes Chamberlin, 1923, with the description of eight new species (Diplopoda, Polydesmida, Paradoxosomatidae), ZooKeys 761, pp. 1-177 : 1

Genus Desmoxytes Chamberlin, 1923

Prionopeltis Pocock, 1895: 828 (preoccupied name). Jeekel 1980a: 652 (synonymised with Desmoxytes ).

Desmoxytes Chamberlin, 1923: 165.

Hylomus Cook & Loomis, 1924: 105. Golovatch and Enghoff 1994: 46 (synonymised with Desmoxytes ).

Pratinus Attems, 1937: 113 (replacement name for Prionopeltis ). Jeekel 1980a: 652 (synonymised with Desmoxytes ).

Ceylonesmus Chamberlin, 1941: 33. Jeekel 1980a: 652 (synonymised with Desmoxytes ).

Pteroxytes Jeekel, 1980a: 655. Golovatch and Enghoff 1994: 46 (synonymised with Desmoxytes ).

Type species

Type species. Desmoxytes coniger Chamberlin, 1923 (MCZ, USA). This species was later synonymised with Desmoxytes planata by Jeekel (1980a).

Included species

(18).

- D. aurata sp. n.

- D. breviverpa Srisonchai, Enghoff & Panha, 2016

- D. cervina (Pocock, 1895)

- D. corythosaurus sp. n.

- D. delfae (Jeekel, 1964)

- D. des Srisonchai, Enghoff & Panha, 2016

- D. euros sp. n.

- D. flabella sp. n.

- D. golovatchi sp. n.

- D. octoconigera sp. n.

- D. perakensis sp. n.

- D. pinnasquali Srisonchai, Enghoff & Panha, 2016

- D. planata (Pocock, 1895) (= D. coniger Chamberlin, 1923, type species)

- D. purpurosea Enghoff, Sutcharit & Panha, 2007

- D. takensis Srisonchai, Enghoff & Panha, 2016

- D. taurina (Pocock, 1895)

- D. terae (Jeekel, 1964)

- D. waepyanensis sp. n.

Desmoxytes s.l. was reviewed by Golovatch and Enghoff (1994), and the diagnosis of the genus was treated in detail again by Golovatch et al. (2012). Here we propose a restricted diagnosis for Desmoxytes s.s. based on morphological characters (gonopod, tegument, paraterga, metaterga, sterna, femora, epiproct, hypoproct) which have been extracted from previous taxonomic works ( Pocock 1895, Chamberlin 1923, 1941, Jeekel 1964, 1980a, Golovatch and Enghoff 1994, Enghoff et al. 2007, Srisonchai et al. 2016).

The name "dragon millipede".

For Desmoxytes sensu Golovatch and Enghoff (1994) we will retain the name "dragon millipede", originally coined by Cook and Loomis (1924) for Hylomus draco . Golovatch et al. (2012) outlined the history of the name "dragon millipede" and further argued that Desmoxytes philippina Nguyen & Sierwald, 2010 (Philippine Isl.), and Desmoxytoides hasenpuschorum Mesibov, 2006 (Australia) have been wrongly assigned to Desmoxytes and "dragon millipedes", respectively.

Diagnosis.

Desmoxytes s.s. differs from other genera of Orthomorphini by the combination of the following characters:

1. Gonopod suberect: solenophore strongly condensed; lamina lateralis developed, lobe-like, without process or spine; lamina medialis distinctly demarcated from lamina lateralis, bearing process and lobes.

2. Metaterga with 2 transverse rows of setiferous setae/ tubercles/ cones/ spines.

3. Paraterga wing-shaped, well-elevated.

4. Sternal cone between male coxae 4 present; subtrapeziform/ subquadrate/ subsemicircular/ incompletely bilobed.

5. Male femora 5 and 6 modified; swollen/humped (exception: D. terae without modification).

General description of the genus Desmoxytes s.s.

The description applies to adult males and females, except for the gonopods section and when “male” is specified (Figs 5, 6, 7, 8). The description hereunder is mainly based on illustrations of D. planata .

SIZE: Body length 16-35 mm (male) 20-38 mm (female), width ca. 1.7-2.5 mm (male) 2.0-3.6 mm (female); size varies between species, usually female wider and longer than male.

COLOUR: Most species in life with aposematic colouration: purplish pink, red, orange, brown, black, brownish black (piceous), brownish red (testaceous). Colour in alcohol: all specimens partly faded after one year’s preservation in alcohol; specimens kept in darkness faded more slowly.

HEAD (Figs 5C, 6A, B, I): Sparsely setose; vertex bare; labrum and genae sparsely setose; epicranial suture conspicuous as a brown or black stripe.

ANTENNAE (Fig. 5 A–C): Often long and slender, rarely short, covered by delicate setation, usually reaching backwards to body ring 3-8 (male) and 3-6 (female) when stretched dorsally. Antennomere lengths 3 = 4 = 5> 2> 6> 1> 7> 8.

COLLUM (Fig. 6A, C): With 1-3 transverse rows of setae/tubercles, the exact number in each row varying between species (sometimes lateral setae/tubercles of anterior row located nearly at the base of paraterga, on anterior margin). Paraterga wing-shaped, usually elevated at ca. 0°-30°.

TEGUMENT (Fig. 6 A–E, G): Often shining, sometimes dull; collum and metaterga often microgranulate; surface below paraterga coarsely or finely microgranulate; prozona finely shagreened. Suture between prozona and metazona usually shallow, quite narrow.

METATERGA (Figs 5A, 6A, C, D, G): With 2 transverse rows of setae/tubercles/cones/spines, number in each row varying between species, lateral cones/spines of posterior row often longer and larger than inner and/or mesal ones. Suture (transverse sulcus) on metaterga present, usually conspicuous on body rings 5-17 in all species. Mid-dorsal (axial) line missing. Pleurosternal carinae forming complete, tooth-liked crests on ring 2, small ridges on ring 3, missing on remaining body rings.

PARATERGA (Figs 5A, B, D, 6 A–E, G, H): Wing-shaped, well-elevated, directed caudolaterad. Callus and shoulder present, usually conspicuous, sometimes inconspicuous. Anterior margin with two distinct notches; on body rings 9, 10, 12, 13, 15-18 a tiny denticle present on lateral margin, near tip (but denticle virtually absent in some species). Elevation of paraterga in male usually higher than in female. Posterior edge concave. Tip pointed and sharp. Ozopore visible from above, round.

TELSON (Fig. 6F, G, N): Epiproct often flattened ventrally, tip often truncate or subtruncate, sometimes emarginate; lateral tubercles often conspicuous, sometimes inconspicuous; apical tubercles usually evident, sometimes indistinct, apically with two pairs of setae. Paraprocts convex. Hypoproct often subtrapeziform, sometimes subsemicircular, rarely subtriangular; caudal margin often round, sometimes emarginate, with two small setiferous tubercles.

STERNA (Figs 5E, 6K): Sparsely setose; cross-impressions faint, usually shallow, rarely quite deep. Sternal lobe between male coxae 4 usually subtrapeziform, subrectangular, subsemicircular or round, varying between species and sometimes varying between populations, usually with two pores on posterior side.

LEGS (Figs 5F, 6J, M): Very long and slender. Podomere lengths 3 = 6> 5> 2 = 4> 1> 7. Male femora 5 and 6 modified, often humped ventrally in middle part, sometimes swollen (exception: D. terae , without modification).

GONOPODS (Figs 6L, 7, 8): Coxa (cx) usually subequal in length to or longer than prefemur, with distoanterior group of seta. Prefemur (pfe) almost half or 2/3 as long as femur. Femur often long. Seminal groove (sg) running entirely on mesal surface of femur. Mesal sulcus (ms) conspicuous, deep; lateral sulcus (ls) conspicuous, usually deep, sometimes shallow. Postfemur shorter than femur, conspicuous. Solenophore (sph) variable between species: lamina lateralis (ll) swollen, sometimes with furrow(s) anterolaterally, sometimes with conspicuous ventral lobe (vll) or ventral ridge (vrl); lamina medialis (lm) variously species-specifically modified, consisting of one process (plm) and two lobes (distal lobe = dlm and broad lobe = blm, dlm and blm demarcated by indentation). Solenomere (sl) usually long, sometimes short.

Distribution and habitat.

From south China to Malaysia. Most species seem to be local endemics (only D. planata is dispersed, certainly by anthropochory, through mainland Southeast Asia and in many islands). Desmoxytes specimens were usually found by ASRU personnel in limestone habitats or on granitic mountains, and some were seen crawling on rocks or vegetation or tree branches (Figure 4).

Key to species of Desmoxytes s.s.