Hylomus Cook & Loomis, 1924

Nguyen, Anh D., Nguyen, Manh-Ha, Nguyen, Thu-Anh T. & Phung, Hong-Luong T., 2019, Review of Dragon Millipedes (Diplopoda, Polydesmida, Paradoxosomatidae) in the Fauna of Vietnam, with Descriptions of Three New Species, Zoological Studies 58 (14), pp. 1-31 : 2-26

Genus Hylomus Cook & Loomis, 1924

Hylomus Cook & Loomis, 1924: 105 ; Attems 1937: 126; Jeekel 1968: 51; Jeekel 1980: 655; Srisonchai et al. 2018a: 15. Synonymized with Desmoxytes by Golovatch & Enghoff (1994: 46), but re-validated by Srisonchai et al. (2018a).

Type species: Hylomus draco Cook & Loomis, 1924 , by original designation.

Diagnosis: The genus can be recognised by a combination of characters: small to large size (12−35 mm long); often brightly coloured; paraterga strongly to exceedingly well developed, wing-, spine- and antler-shaped; metazonal surface often more or less roughly granulate, rarely smooth; epiproct of telson sometimes modified with hypertrophied setiferous tubercles near tip; male leg femora 5/6/7/9 often inflated or humped ventrally; gonopod suberect, seldom subfalcate; solenophore and solenomere usually shortened.

Remarks: The genus is widely distributed in southern China and Vietnam. Few species are found in Laos and Thailand. The distribution of the genus Hylomus in Vietnam is shown in figure 1.

Key to species of the genus Hylomus species in Vietnam

1. Paraterga wing-shaped ........................................... H. spectabilis

- Paraterga antler- or spine-shaped ( Figs. 3 , 7 , 9 , 11 ) ................... 2

2. Paraterga antler-shaped ( Figs. 3 , 7 , 11 ) ...................................... 3

- Paraterga spine-shaped ( Fig. 9 ) ................................................ 11

3. Epiproct unmodified, without conspicuous setiferous knobs near tip ( Fig. 18 A−B) ......................................................................... 4

- Epiproct modified, with several evident setiferous knobs near tip ( Figs. 7F , 28B )............................................................................ 7

4. Metaterga smooth, more or less shining. Male femora unmodified ......................................................................................... H. asper

- Metaterga rough, dull, granular. Male femora modified, inflated. ..................................................................................................... 5

5. Metaterga with more than 4 + 4 posterior setiferous spines on midbody segments ( Fig. 17A ). Body pale or weakly pigmented. Lamina lateralis of gonopod solenophore with densely setose region ( Figs. 19−20 ) ................................................... H. songoku

- Metaterga with less than 4 + 4 posterior setiferous spines on midbody segments. Body pigmented. Lamina lateralis of gonopos solenophore without densely setose region ................................ 9

6. Metaterga with 3 + 3 posterior setiferous spines. Male femora 6, 7 and 9 humped ventrally. Fifth sternum with a pair of tubercles between coxae 4 ....................................................... H. cervarius

- Metaterga with 2 + 2 posterior setiferous spines. Male femora 6 and 7, sometime femur 5 modified, each with a large hump on ventral side. Fifth sternum with either rectangular process or bifid trapeziform lamina between coxae 4.......................................... 7

7. Body light or darkish brown. Fifth sternum with a bifid trapeziform lamina between coxae 4.......................................... 8

- Body reddish or pinkish. Fifth sternum with four round tubercles on a prominent, elevated, rectangular lamina between male coxae 4 .................................................................................. H. enghoffi

8. Male femora 6, 7 humped ventrally ( Fig. 28D ). Tip of solenophore broadly rounded lobuliform ( Figs. 29−30 ) ............... ........................................................................................ H. namek

- Male femora 6, 7, sometimes 5, humped ventrally ( Fig. 23B ). Tip of solenophore acute ( Figs. 24−25 ) ............................. H. saiyans

9. At least 3 + 3 posterior metatergal spines on metaterga........... 10 - Only 1 + 1 posterior poor setae on metaterga ( Fig. 3B, D ) ........... ............................................................................... H. cattienensis

10. Colour pink to red. Metaterga with numerous microsetae, and 4 + 4 posterior spines ( Fig. 4A, B, D, E ) ............................ H. pilosus

- Colour dark to castaneous brown. Metaterga with microgranulation, and 3 + 3 posterior spines ............ H. proximus

11. A row of 1 + 1 posterior spines on metaterga. Gonopod subfalcate, femorite slightly curved; solenomere long .................. .................................................................................... H. specialis

- A row of 2 + 2 posterior tubercles/spines on metaterga. Gonopod falcate; solenophore short, pointed terminally ......................... 12

12. Fifth sternum with two independent setiferous tubercles between coxae 4. Antenna long and slender.............................. H. grandis

- Fifth sternum with a bifid setiferous trapeziform lamina between coxae 4. Antenna short and stout ( Fig. 9B ) ................... H. holstii

Figures

Fig. 3. Hylomus cattienensis (Nguyen, Golovatch & Anichkin, 2005) from Cat Tien National Park. Anterior part, lateral view (A), dorsal view (B), ventral view (C); body rings 10−12, dorsal view (D), lateral view (E); posterior part, lateral view (F), ventral view (G); gonopods, ventral view (H); sternite 5, ventral view (I). Anterior part, lateral view (A), dorsal view (B), ventral view (C); body rings 10−12, dorsal view (D), lateral view (E); posterior part, lateral view (F), ventral view (G); gonopods, ventral view (H); sternite 5, ventral view (I). No scale bars were inserted while taking photographs for this figure. This figure emphasises colouration, shapes of paraterga (Pa), metaterga (Me), head (He), collum (Co), gonopods (Go), sternal tubercles (st), epiproct (Epi) and hypoproct (Hy).

Fig. 7. Hylomus enghoffi (Nguyen, Golovatch & Anichkin, 2005) from Phong Nha – Ke Bang National Park. Anterior part, dorsal view (A), lateral view (B). Middle part, dorsal view (C). Posterior part, lateral view (D), ventral view (E). Hypoproct (F). No scale bars were inserted while taking photographs for this figure. This figure emphasises colouration, shapes of paraterga (Pa), metaterga (Me), collum (Co), epiproct (Epi) and hypoproct (Hy).

Fig. 9. Hylomus hostilis (Golovatch & Enghoff, 1994) from Tam Dao National Park.

Fig. 11. Hylomus pilosus (Attems, 1937) from Cat Tien National Park. Anterior part, dorsal view (A), lateral view (B), ventral view (C). Midbody part, dorsal view (D). Posterior part, dorsal view (E), ventral view (F). No scale bars were inserted while taking photographs for this figure. This figure emphasises colouration, shapes of head (He), collum (Co), paraterga (Pa), metaterga (Me), sterna (Ste), epiproct (Epi) and hypoproct (Hy).

Fig. 18. Hylomus songoku sp. nov. from Xuan Son National Park. Holotype. Epiproct, dorsal view (A). Hypoproct and epiproct, ventral view (A). Sternal process between coxae 4, subventral view (C). Leg 6-7 (D). Scale bar = 1 mm.

Fig. 28. Hylomus namek sp. nov. from Ha Giang Province. Holotype. Epiproct, lateral view (A). Epiproct and hypoproct, ventral view (B). Sternal process between coxae 4 (C). Legs 5−6 (D). Scale bars: A−B = 1 mm; C−D = 0.5 mm.

Fig. 17. Hylomus songoku sp. nov. from Xuan Son National Park. Holotype. Segment 10, dorsal view (A). Posterior part, lateral view (B), dorsal view (C), ventral view (D). Scale bar = 1 mm.

Fig. 19. Hylomus songoku sp. nov. from Xuan Son National Park. Holotype. Right gonopod, lateral view (A), mesal view (B, C). Scale bars: A-B = 1 mm; C = 0.1 mm. (Note: solenophore in figure 16C was broken while taking SEM image)

Fig. 20. Hylomus songoku sp. nov. from Xuan Son National Park. Holotype. Right gonopod, lateral view (A), mesal view (B), dorsal view (C). Scale bar = 1 mm.

Fig. 29. Hylomus namek sp. nov. from Ha Giang Province. Left gonopod, mesal view (A), lateral view (B). Scale bar = 1 mm.

Fig. 30. Hylomus namek sp. nov. from Ha Giang Province. Left gonopod, mesal view (A), lateral view (B). Scale bar = 1 mm.

Fig. 23. Hylomus saiyans sp. nov. from Cuc Phuong National Park. Holotype. Sternal process between coxae 4, subposterior view (A). Legs 5−6−7 (B). Scale bars: A = 0.5 mm; B = 1 mm.

Fig. 24. Hylomus saiyans sp. nov. from Cuc Phuong National Park. Holotype. Right gonopod, lateral view (A), mesal view (B). Scale bar = 1 mm.

Fig. 25. Hylomus saiyans sp. nov. from Cuc Phuong National Park. Holotype. Right gonopod, lateral view (A), mesal view (B).

Fig. 4. Hylomus cattienensis (Nguyen, Golovatch & Anichkin, 2005) from Cat Tien National Park. Right gonopod, lateral view (A), mesal view (B). Scale bar = 0.5 mm.