Gigaxytes suratensis Srisonchai, Enghoff & Panha

Srisonchai, Ruttapon, Enghoff, Henrik, Likhitrakarn, Natdanai & Panha, Somsak, 2018, A revision of dragon millipedes III: the new genus Gigaxytes gen. nov., with the description of three new species (Diplopoda, Polydesmida, Paradoxosomatidae), European Journal of Taxonomy 463, pp. 1-43: 31-39

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Gigaxytes suratensis Srisonchai, Enghoff & Panha

gen. et sp. nov.

Gigaxytes suratensis Srisonchai, Enghoff & Panha  gen. et sp. nov.

( Figs 19–24View Fig. 19View Fig. 20View Fig. 21View Fig. 22View Fig. 23View Fig. 24)


Male femora 5, 6 and 7 with an apophysis. Similar in this respect to G. parvoterga  gen. et sp. nov., but differs from this species by having paraterga longer; collum usually with 4+4 cones/spines (intermediate row); metaterga 2–8 usually with 4+4 cones/spines (anterior row), 4+4 cones/spines (intermediate row) and 4+4 cones/spines (posterior row); metaterga 9–12 usually with 5+5 cones/spines (anterior row), 5+5 cones/spines (intermediate row) and 5+5 cones/spines (posterior row); metaterga 13–19 usually with 6+6 cones/spines (anterior row), 6+6 cones/spines (intermediate row) and 6+6 cones/spines (posterior row).


The specific epiteth is a Latin adjective, referring to the province where the type locality occurs.

Material examined

Holotype THAILAND: ♂, Surat Thani Province, Phanom District, Ban Song Phi Nong , 8º50′54″ N, 98°44′16″ E, ca. 117 m a.s.l., 7 Aug. 2016, ASRU members leg. ( CUMZ-pxDGT00182).GoogleMaps 

Paratypes THAILAND: 3 ♂♂, 6 ♀♀, 13 juveniles, same data as for holotype ( CUMZ-pxDGT00183-204);  1 ♂, 1 ♀, same data as for holotype ( ZMUC00040248View Materials)  .

Additional specimens

THAILAND – Surat Thani Province: 1 ♂, 1 broken ♂ – right gonopod lost, 1 ♀, 1 broken ♀, 4 juveniles, Ban Ta Khun District, Ratchaprapa Dam, 8º57′22″ N, 98°48′22″ E, ca. 53 m a.s.l., 8 Oct. 2008, ASRU members leg. ( CUMZ);GoogleMaps  1 ♂ – gonopods lost, Ban Ta Khun District , Khao Wong Water Supply Station , 8º55′47″ N, 98°56′25″ E, ca. 91 m a.s.l., 9 Oct. 2008, ASRU members leg. ( CUMZ);GoogleMaps  1 ♂, Khirirat Nikhom District , Wat Satit Khirirom, 9º01′48″ N, 98°59′12″ E, ca. 50 m a.s.l., 10 Jul. 2017, ASRU members leg. ( CUMZ);GoogleMaps  4 broken ♂♂, 3 broken ♂♂ – gonopods lost, 1 ♀, Phanom District , Khlong Phanom National Park, 8º52′44″ N, 98°40′26″ E, ca. 68 m a.s.l., 28 Aug. 2007, ASRU members leg. ( CUMZ)GoogleMaps  ; 1 juvenile, Phanom District, Wat Tham Wararam, 8º53′07″ N, 98°40′01″ E, ca. 51 m a.s.l., 5 Aug. 2014, ASRU members leg. ( CUMZ);GoogleMaps  1 ♂ remaining rings 14–20, 1 ♂ – gonopods lost, 1 broken ♀, Unknown location (probably in Ban Ta Khun District ), ASRU leg. ( CUMZ).GoogleMaps 


SIZE. Length 36–40 mm (male), 38–40 mm (female); width of midbody metazona ca. 2.9 mm (male), 3.7 mm (female). Width of head <collum <2 ≤ 3 <4 <5–16, thereafter body gradually tapering towards telson.

COLOUR ( Fig. 19A –EView Fig. 19). Specimens in life with body pinkish brown; some specimens with a dark middorsal band; paraterga and antennae dark brown (except distal part of antennomere 7 and antennomere 8 whitish); head, epiproct and legs brown; metaterga, prozona and surface below paraterga (upper part) pinkish brown; collum pinkish brown/brown; surface below paraterga (lower part) brownish pink; tip of paraterga and sterna pale brown to whitish; a few basal podomeres pale brown. Colour in alcohol: after 10 years changed to pale brown; head, antennae, collum, metaterga, paraterga, surface below paraterga, sterna, epiproct and legs pale brown.

COLLUM ( Fig. 20AView Fig. 20). With three transverse rows of setiferous cones/spines, 5(6)+5 cones/spines in anterior row, 4(3)+4(3) cones/spines in intermediate row and 4(3/5)+4(5) cones/spines in posterior row (lateral cones/spines of anterior row located at base of collum paraterga; lateral cones/spines of posterior row displaced anteriad almost halfway to intermediate); paraterga of collum elevated at ca. 30º –45º.

ANTENNAE ( Fig. 20DView Fig. 20). Moderately long and slender, reaching to body ring 5 or 6 (male) and 4 or 5 (female) when stretched dorsally.

TEGUMENT. Stricture between prozona and metazona wide, quite deep.

METATERGA ( Fig. 20A –CView Fig. 20). With three transverse rows of setiferous cones/spines; metaterga 2–8 with 4(5)+4(5) cones/spines in anterior row, 4(3)+4(3/5) cones/spines in intermediate row and 4(3/5)+4(3/5) cones/spines in posterior row; metaterga 9–12 with 5(6/7)+5(6) cones/spines in anterior row, 5(6)+5(6) cones/spines in intermediate row and 5(6/7)+5(6/7) cones/spines in posterior row; metaterga 13–19 with 6(5/7/8)+6(5/7/8) cones/spines in anterior row, 6(5/7/8)+6(5/7/8) cones/spines in intermediate row and 6(5/7/8)+6(5/7/8) cones/spines in posterior row.

PLEUROSTERNAL CARINAE. On body ring 2 long, crest-like; on ring 3 a long ridge; on ring 4 a short ridge; thereafter missing.

PARATERGA ( Figs 20A –C, IView Fig. 20, 21A –BView Fig. 21). Moderately long, directed caudolaterad on body rings 2–17, elevated at ca. 45º –60º (male) 40º –50º (female), directed increasingly caudad on body rings 18–19.

TELSON ( Fig. 21C –GView Fig. 21). Tip of epiproct usually subtruncate (in some specimen slightly emarginate); apical tubercles inconspicuous. Hypoproct subtrapeziform; caudal margin usually subtruncate (in some specimens slightly round), with inconspicuous setiferous tubercles.

STERNUM ( Fig. 21H –JView Fig. 21). On body ring 5 with a swollen lobe; posterior surface of lobe with a pore borne on a short cylindrical stalk.

LEGS ( Fig. 20E –HView Fig. 20). Male femora 5, 6 and 7 with an apophysis.

GONOPODS ( Figs 22–23View Fig. 22View Fig. 23). Coxa subequal in length to femorite. Cannula quite short and stout. Femorite long, slender, curved. Solenophore wide laterally: lamina lateralis broad: lamina medialis very wide, distally blunt, in situ directed mesoventrad.

Distribution and habitat

Gigaxytes suratensis  gen. et sp. nov. is known only from Surat Thani Province. It has been collected from limestone habitats hiding under dead leaves. We cound not access many isolated limestone moutains nearby the type locality, we assume, however, that this species might have a distribution running along the huge limestone mountain ranges in Khaosok and Khlong Phanom National Parks. According to the current data, the new species is dispersed narrowly, we therefore regard G. suratensis  gen. et sp. nov. as endemic for Thailand. The new species was found together with Desmoxytes corythosaurus Srisonchai, Enghoff & Panha, 2018  at Ban Song Phi Nong and Wat Satit Khirirom; Desmoxytes cervina  at Wat Satit Khirirom.


Across the range of this species there are some variations in tip of epiproct (subtruncate in some specimens, slightly emarginate in others) and in shape of caudal margin of hypoproct (subtruncate in some specimens, in others slightly round).


Chulalongkorn University Museum of Natural History