Gigantomorpha Jeekel, 1963

Ng, Ting Hui, Srisonchai, Ruttapon, Golovatch, Sergei I., Sutcharit, Chirasak, Panha, Somsak, Latim, Martinah & Likhitrakarn, Natdanai, 2025, A taxonomic study of millipede genera, Orangutana Golovatch, 1996 and Gigantomorpha Jeekel, 1963 (Diplopoda, Polydesmida, Paradoxosomatidae), with description of four new species from Sabah, Borneo, East Malaysia, European Journal of Taxonomy 987, pp. 221-248 : 224-239

Genus Gigantomorpha Jeekel, 1963

Gigantomorpha Jeekel, 1963: 106 (D, K).

Gigantomorpha – Jeekel 1968: 116 (L); 1979: 164 (L). — Golovatch 1996: 169 (M, K). — Nguyen & Sierwald 2013: 1244 (L).

Type species

Gigantomorpha immanis Jeekel, 1963 , by original designation.

Emended diagnosis

Body medium to large-sized (ca 20–55 mm long, ca 2.8–8.0 mm wide), with 20 rings. Paraterga from moderately to strongly developed. Transverse metatergal sulci distinct. Legs moderate in length to rather long, without modifications. Adenostyles absent. Sternal lamina present between male coxae 4, following sternites modified with a cone near coxa, or unmodified.

Gonopods slightly curved, relatively complex; coxa moderate in size, subcylindrical, sparsely setose distoventrally, without tubercles; prefemoral (= densely setose) part of telopodite relatively short, 1/5– 1/3 as long as acropodite; femoral part long and slender, almost straight, without evidence of torsion (= seminal groove running only mesally), often slightly enlarged distally, with a clear-cut, oblique, distolateral sulcus demarcating a postfemoral part; solenophore moderately strongly curved mesad or caudomesad, consisting of well-developed laminae lateralis and medialis, yet with lamina medialis usually larger than lamina lateralis, lamina medialis developed only in distal part of postfemoral part, where it gives rise to a more or less complicated laminate process, tip of solenophore deeply bifid, each prong with either minute denticles or lappets, or completely reduced. Solenomere flagelliform, almost fully sheathed by solenophore.

Other species included

Gigantomorpha aterrima Jeekel, 1963 , G. cornalata Jeekel, 1963 , G. fasciata ( Attems, 1898) , G. mutilata Golovatch, 1996 , G. pallida Jeekel, 1963 , G. socialis ( Carl, 1912) , G. spinescens Jeekel, 1963 , G. transmontana Jeekel, 1982 , G. trichopleura Jeekel, 1963 , as well as G. alabensis Ng & Likhitrakarn sp. nov., G. mesilauensis Ng & Likhitrakarn sp. nov. and G. sayapensis Ng & Likhitrakarn sp. nov.

Remarks

The genus Gigantomorpha was originally established by Jeekel (1963) with the designation of G. immanis as type species. That work included descriptions of seven new species from Borneo and the transfer of two previously described species, Pratinus fasciatus Attems, 1898 from Borneo and Pratinus socialis Carl, 1912 from Sulawesi, due to uncertainties regarding the taxonomic status of Pratinus Attems, 1937 ( Jeekel 1963). Subsequently, Golovatch (1996) re-examined the type material of G. immanis , refining the variation range of the ambiguities in some morphological characters. His study provided the detailed redescription and illustrations of G. immanis and included the description of a new species from Bali ( Golovatch 1996).

Key to the presently known species of Gigantomorpha Jeekel, 1963 (modified after Golovatch 1996)

1. Gonopodal tip deeply and prominently bifid, with robust branches. Sternites modified, with a cone near each coxa ................................................................................................................................... 6

– Gonopodal tip very small, bi- to trifid, with reduced and less distinct branches ( Figs 3–4 , 6–7 , 9–10 ). Sternites typical, generally without cones near coxae but with exceptions ...................................... 2

2. Larger: midbody width 5.5–5.6 mm. Pleurosternal carinae present until ring 10. Sternites modified, with a cone near each coxa. Male tarsal brushes absent .................... G. transmontana Jeekel, 1982

– Smaller: midbody width at most 5.1 mm. Pleurosternal carinae present (not extending beyond ring 8). Sternites typical, without cones near coxae. Male tarsal brushes present at least until legs of ring 4.................................................................................................................................................. 3

3. Smaller: midbody width 2.8–3.2 mm (♂, ♀). Sternal cones between male coxae 4 fused basally into a single lamina. Male tarsal brushes present until legs of ring 4. Bali. G. mutilata Golovatch, 1996

– Larger: midbody width at least 3.6 mm (♂). Sternal cones between male coxae 4 isolated ( Figs 2H– I , 5H–I , 8I–J ). Male tarsal brushes present at least until legs of ring 16. Sabah, northern Borneo .. 4

4. Smaller: midbody width 3.6–4.4 mm (♂, ♀). Paraterga less strongly bordered ( Fig. 5A, C, F ). Sternal cones present only between male coxae 4. Gonopodal lamina lateralis (ll) and lamina medialis (lm) subequal in length, long and slender ( Fig. 7A ) ............. G. mesilauensis Ng & Likhitrakarn sp. nov.

– Larger: midbody width at least 4.8 mm. Paraterga especially strongly bordered ( Figs 2A, C, F , 8B, D, F ). Sternal cones present between both male coxae 4 and 5. Gonopodal lamina medialis (lm) larger than lamina lateralis (ll), expanded apically ( Figs 3A–D , 4A–B , 9A–D, F , 10A–C ) ............. 5

5. Pleurosternal carinae present until ring 7. Male legs shorter, ca 1.3–1.5 times as long as midbody height. Male tarsal brushes present until legs of ring 18. Gonopodal lamina lateralis (ll) unciform, tip, with two subequal apical lobes ( Figs 9 , 10B–C ) ........ G. sayapensis Ng & Likhitrakarn sp. nov.

– Pleurosternal carinae present until ring 4. Male legs longer, ca 1.5–1.7 times as long as midbody height. Male tarsal brushes present until legs of ring 16. Gonopodal lamina lateralis (ll) with a single subtruncate tip ( Figs 3A, C , 4B ) ......................................... G. alabensis Ng & Likhitrakarn sp. nov.

6. Lateral edges of collum rounded caudally. Paraterga 2 directed somewhat ventrad, lying distinctly below level of paraterga 3. Male femora straight ............................................................................. 7

– Lateral edges of collum angular caudally. Paraterga 2 somewhat upturned, nearly level to paraterga 3. Male femora distinctly arched .......................................................................................................... 8

7. Smaller: midbody width 5.0– 5.4 mm (♂, ♀). A pattern of 4(5)+4(5) very small tubercles near caudal margin of metaterga. Paraterga set relatively low (at about mid-height on male ring 4), below them almost all rings with an irregular row of setae along caudal margin. Pleurosternal carinae present until ring 17 ........................................................................................... G. trichopleura Jeekel, 1963

– Larger: midbody width 6.3–8.0 mm (♂, ♀). Usually 3+3 larger tubercles near caudal margin of metaterga. Paraterga clearly set higher (at about 1/3 height on male ring 4), without setae below them. Pleurosternal carinae present until ring 14 or 15 ........................... G. spinescens Jeekel, 1963

8. Body ring dark brown to blackish, with paraterga and a middorsal band pale brownish. Gonopodal femoral part rather strongly constricted about midlength ........................ G. fasciata ( Attems, 1898)

– Colouration rings in ethanol without continuous middorsal pale band. Gonopodal femoral part without constriction .......................................................................................................................... 9

9. Colouration in ethanol uniformly blackish, with only the caudal corners of the paraterga brown. Male proximal podomeres covered with short, curved setae, femora less strongly arched ............... ..................................................................................................................... G. aterrima Jeekel, 1963

– Colouration in ethanol not uniformly dark; dorsum may be somewhat paler, occasionally with a pale central spot on prozonites, or dark with contrasting yellow areas. Paratergal caudal corners always yellowish. Male legs with long, erect setae, and femora more strongly arched ............................. 10

10. Pleurosternal carinae present until ring 16 or 17 .............................................................................11

– Pleurosternal carinae present until ring 14 or 15 ............................................................................ 12

11. Colouration of dorsum rather uniformly pale brownish gray. Paraterga distinctly projecting caudally past rear tergal margin from ring 11 or 12 onwards. East Borneo ................ G. pallida Jeekel, 1963

– Colouration black-brown with caudal corners of paraterga yellow. Paraterga extending caudally past rear tergal margin from ring 15 onwards. South Sulawesi ............................ G. socialis ( Carl, 1912)

12. Paraterga largely strongly elevated above dorsum. Pleurosternal carinae present until ring 14 or 15. Male legs more slender, proximal podomeres without ventral brushes of setae ................................ .................................................................................................................... G. cornalata Jeekel, 1963

– Paraterga more or less level to dorsum. Pleurosternal carinae present until ring 9 or 10. Male legs more strongly incrassate, with ventral brushes on all podomeres .............. G. immani s Jeekel, 1963

Figures

Fig. 3. Gigantomorpha alabensis Ng & Likhitrakarn sp. nov., holotype, ♂ (SP 14836), left gonopod. A–B. Sublateral and mesal views, respectively. C–F. Sublateral, mesal, subcaudal and suboral views, respectively. Colours: red = lamina medialis (lm); green = lamina lateralis (ll). Red arrows = evident incision. Abbreviation: sl = solenomere. Scale bars = 0.2 mm.

Fig. 4. Gigantomorpha alabensis Ng & Likhitrakarn sp. nov., holotype, ♂ (SP 14836), left gonopod. A–D. Mesal and lateral views, respectively. Abbreviations: cx = coxa; fe = femoral part; ll = lamina lateralis; lm = lamina medialis; pfe = prefemoral part; sl = solenomere. Scale bar = 0.2 mm.

Fig. 6. Gigantomorpha mesilauensis Ng & Likhitrakarn sp. nov., holotype, ♂ (BOR/MYR 90), left gonopod. A–B. Sublateral and submesal views, respectively. C–F. Distal part, sublateral, submesal, suboral, and subcaudal views, respectively. Colours: red = lamina medialis (lm); green = lamina lateralis (ll). Abbreviation: sl = solenomere. Scale bars = 0.2 mm.

Fig. 7. Gigantomorpha mesilauensis Ng & Likhitrakarn sp. nov., holotype, ♂ (BOR/MYR 90), left gonopod. A–B. Mesal and lateral views, respectively. Abbreviations: cx = coxa; fe = femoral part; ll = lamina lateralis; lm = lamina medialis; pfe = prefemoral part. Scale bar = 0.2 mm.

Fig. 9. Gigantomorpha sayapensis Ng & Likhitrakarn sp. nov., holotype, ♂ (SP 14835), left gonopod. A–B. Submesal and sublateral views, respectively. C–F. Distal part, sublateral, submesal, subcaudal and suboral views, respectively. Colours: red = lamina medialis (lm); green = lamina lateralis (ll). Abbreviation: sl = solenomere. Scale bars = 0.2 mm.

Fig. 10. Gigantomorpha sayapensis Ng & Likhitrakarn sp. nov., holotype, ♂ (SP 14835), left gonopod. A–D. Suboral, mesal, lateral and subcaudal views, respectively. Abbreviations: cx = coxa; fe = femoral part; ll = lamina lateralis; lm = lamina medialis; pfe = prefemoral part; sl = solenomere. Scale bars = 0.2 mm.

Fig. 2. Gigantomorpha alabensis Ng & Likhitrakarn sp. nov., holotype, ♂ (SP 14836). A–B. Anterior part of body, dorsal and lateral views, respectively C–D. Rings 10 and 11, dorsal and lateral views, respectively. E–G. Posterior part of body, lateral, dorsal, and ventral and views, respectively.H–I. Sternal cones between coxae 4 indicated by red arrows, caudal and sublateral views, respectively.

Fig. 5. Gigantomorpha mesilauensis Ng & Likhitrakarn sp. nov., holotype, ♂ (BOR/MYR 90). A–B. Anterior part of body, dorsal and lateral views, respectively. C–D. Rings 10 and 11, dorsal and lateral views, respectively. E–G. Posterior part of body, lateral, dorsal and ventral views, respectively. H–I. Sternal cones between coxae 4 indicated by red arrows, caudal and sublateral views, respectively.

Fig. 8. Gigantomorpha sayapensis Ng & Likhitrakarn sp. nov., holotype, ♂ (SP 14835). A. Habitus, live colouration. B–C. Anterior part of body, dorsal and lateral views, respectively. D–E. Rings 10 and 11, dorsal and lateral views, respectively. F–H. Posterior part of body, dorsal, ventral and lateral views, respectively. I–J. Sternal cones between coxae 4 indicated by red arrows, caudal and sublateral views, respectively.