1 ♂, 7 ♀, 1 fragment (MNHN JC 354), Vanuatu, Espirito Santo Island, Natawa forest, small doline Arifos, 167.183167E, 15.2962S, sieved litter & Berlese extraction, 24.09.2006, leg. L. Deharveng & A. Bedos (SK06-24-24); 1 ♂ (SEM), same locality, date and collectors (SK06-24-22); 3 ♀ (MNHN JC 354), Espirito Santo Island, Boutmas, forest near entrance to Cave Fapon, 166.9648833E, 15.33101667S, 380 m a.s.l., litter, Berlese extraction, 08.09.2006, leg. L. Deharveng & C. Rahmadi (SK06-08-24).

Length of adults of both sexes 4–6 mm (♂, ♀), width of midbody pro- and metazonae ca 0.3 and 0.4 mm, respectively. Coloration in alcohol from uniformly pallid to light yellowish.

Body with 19 (♂) or 20 (♀) segments. Tegument mainly dull, at most slightly shining, texture very delicately alveolate. Head densely pilose throughout; epicranial suture superficial and thin (Fig. 1A); isthmus between antennae about 1.5 times as broad as diameter of antennal socket. Antennae short, reaching only behind (♂) or midway of collum (♀) when stretched dorsally, not geniculate, very clearly clavate, especially so due to largest antennomere 6, the latter with a small, but evident distodorsal group of bacilliform sensilla.

Body moniliform, especially so in ♂ (Fig. 1D–F). In width, collum << head < segment 2 < 3 = 4 < 5(6) = 15 (♂, ♀), thereafter body gradually tapering towards telson. Paraterga very poorly developed, mainly represented by setigerous tubercles (Fig. 1A–F, H–K), starting from collum, set rather low (at about upper 1/3–1/2 of segment’s height), leaving a highly convex dorsum (Fig. 1A–C & K). Caudal corner of postcollum paraterga increasingly tuberculiform, mainly clearly rounded, not extending behind rear tergal margin. Pore formula normal; ozopores evident, round, lying dorsolaterally on top of caudolateral tubercle of paraterga very close to lateral margin, more remote from caudal margin (Fig. 1M). Collum subovoid, each following metatergum with 3 transverse rows of mostly long, pointed, very faintly ribbed, helicoid setae largely borne on 6+6 unusually high tubercles, these being especially prominent in last row (Fig. 1A–F). Stricture between pro- and metazonae deep, rather narrow and smooth. Limbus thin and entire, not microdenticulate. Pleurosternal carinae absent (Fig. 1A). Epiproct short, conical, directed caudoventrally; pre-apical papillae evident (Fig. 1C, F, J). Hypoproct nearly semi-circular (Fig. 1J), setiferous papillae at caudal corners very clear, stalk-shaped and well separated.

Sterna without modifications, broad, flat, poorly setose (Fig. 1H–J). Stigma openings flat, beset with dense and long filaments (Fig. 1N). Legs in ♀ and juveniles clearly shorter and slenderer, ca 1.0–1.1 times as long as body height, in ♂ somewhat incrassate and ca 1.3–1.4 times as long as body height (Figs 1B, 2A); tarsi longest; sphaerotrichomes missing (Fig. 2A). Each ♂ coxa 2 with a short, cylindrical, distoventral gonapophysis.

Gonopod aperture transversely oblong-oval, taking up most of ventral part of metazonite 7, its edges nowhere elevated (Figs 1H, 2B). Gonopods (Fig. 2B–E) with rather moderately large, globose, bare, ventrolaterally papillate, medially fused coxae carrying normal cannulae mesally. Telopodite strongly elongate and curved, subunciform, bipartite, directed mesad and crossing in situ, each at about midway with a short, mesal, calyciform process (p) (= solenomere) terminating a fully mesal seminal groove, with neither an accessory seminal chamber nor a hairy pulvillus. Main branch (b) (= solenophore) bifid and slightly expanded subterminally.

This species, originally described from a single ♂ taken in a cave in Lelet Plateau, New Ireland, Papua New Guinea (Hoffman 1987), appears to be common and widespread in Vanuatu. However, among the literally hundreds of specimens taken on Espiritu Santo and Malo islands by the famous SANTO 2006 expedition, held by the MNHN (Bouchet et al. 2009, 2011, 2012), there were only two adult males. This might be evidence of seasonality or partial parthenogenesis, or both.

The original description is quite detailed and nicely illustrated (Hoffman 1987) and we are certain about the identity of our Vanuatu samples. We provide SEM images (Figs 1 and 2) to document the identity and to complement Hoffman’s (1987) description.

19 segments (♂, ♀); ozopores wanting; ♂ vertex modified or not; ♂ antennomere 6 sometimes with a conspicuous dorsoparabasal stump; paraterga absent to rather well developed, 3 rows of 3+3 or 4+4, short or long, bacilli- and/or claviform metatergal setae (regardless of lateral setae on or instead of paraterga); gonopod coxae with gonocoel not deep; telopodites clearly exposed, mostly or considerably represented by elongate prefemoral parts, at most only moderately curved, medially subcontiguous and held parallel to each other; acropodites, or solenophores (sph), lying distal to prefemoral parts shortened, only sometimes set off basally by a ventral sulcus, subtruncate, usually more or less coaxial with prefemoral parts, but sometimes extended laterad into a distinct process; solenomere (sl) subapical, rather long to vestigial.

To emphasize the lack of ozopores, feminine.

Aporodesmella securiformis sp. n., by present designation.

The new genus is unique among the Trichopolydesmoidea for its complete loss of ozopores. Among Oriental Trichopolydesmidae, Aporodesmella gen. n. seems to be especially similar to Peronorchus, sharing with it not only 19 body segments in both sexes, but also the gonopods demonstrating a modest gonocoel, elongate, clearly exposed and modestly curved telopodites which are (sub)contiguous medially and held parallel to each other (and to the main body axis), the solenophore being enlarged, more or less cup-shaped and membranous while the solenomere is a short subapical process or tooth. However, the prefemoral (= densely setose) part of the gonopod in Peronorchus is clearly shorter.

The following three new species are attributed to Aporodesmella gen. n.

Holotype ♂ (MNHN JC 355), Vietnam, Kien Giang Province, Kien Luong, Hon Chong, Nui Bai Voi, 104.618E, 10.218N, soil, Berlese extraction, 02.06.2008, leg. L. Deharveng & A. Bedos (Vn08-045).

Paratypes: 1 ♂, 4 ♀ (MNHN JC 355), 1 ♂, 1 ♀ (ZMUM ρ2346), 1 ♂ (SEM), same locality, together with holotype; 2 ♂, 1 ♀ (MNHN JC 355), 1 ♂ (SEM), same province, Kien Luong, Hon Chong, Nui Hang Tien, litter & soil, Berlese extraction, 02.06.2008, leg. Ly Ngoc Sam (Vn08-065); 3 ♂ (MNHN JC 355), 1 ♂ (SEM), same data (Vn08-066).

To emphasize the axe-shaped solenophore.

Differs from congeners except Aporodesmella similis sp. n. by the presence of a remarkable dorsoparabasal stump on ♂ antennomere 6, from Aporodesmella similis sp. n. and other congeners by a peculiar, unusually short, axe-shaped solenophore and a simple, lanceolate, shorter and stout solenomere.

Length of adults ca 2.8–2.9 mm (♂, ♀), up to 3.0 mm (♀), width of midbody pro- and metazonae 0.15 and 0.2 (♂, ♀), up to 0.2 and 0.25 mm (♀), respectively. Coloration in alcohol uniformly pallid, tegument translucent.

Body moniliform, with 19 segments (♂, ♀). Tegument mainly dull, at most slightly shining, texture very delicately alveolate and microgranulate. Head without modifications, densely pilose throughout except occiput; epicranial suture superficial and thin; genae squarish (Fig. 3A, D, G); gnathochilarium narrow, setae dense and short (Fig. 4A); isthmus between antennae about as broad as diameter of antennal socket (Fig. 3G). Antennae very short, reaching only behind collum (♂, ♀) when stretched dorsally, not geniculate, strongly clavate due to an abruptly and particularly enlarged antennomere 6, the latter with a usual, tight, distodorsal group of numerous bacilliform sensilla, but in ♂ also with a large, highly conspicuous, dorsoparabasal, rounded stump (s); antennomere 5 with a loose distodorsal group of only a few tiny sensilla, 7^th with a tiny mid-dorsal knob (Figs 3G, J, 4A).

In width, head > segment 2 > collum = segment 3 = 4 > 5(6) = 16 (♂, ♀), thereafter body gradually tapering towards telson (Fig. 3D–F). Paraterga wanting, metazonae subcylindrical, dorsum strongly convex (Fig. 3A–I). Ozopores totally absent (Fig. 3A, B, D–F, K). Collum subovoid, each following metatergum mostly with 4+4 rather long, slightly blunted, subclavate to subbacilliform, thickened and longitudinally ribbed setae arranged in 3 transverse regular rows and borne on minute knobs (Fig. 3A–F, K–M). Stricture between pro- and metazonae rather wide and shallow, scaly like rear part of prozonae. Limbus very fine and microcrenulate (Fig. 3L). Pleurosternal carinae thin lines (Fig. 3A, B, H). Epiproct short, conical, directed caudoventrally; pre-apical papillae small (Fig. 3C, F, I). Hypoproct subtrapeziform, caudal setigerous papillae evident and well separated (Fig. 3I).

Sterna without modifications, rather broad and sparsely setose (Fig. 3H). Legs short, ca 1.3–1.4 (♂) or 1.1–1.2 times as long as midbody height (♀); ♂ prefemora, femora, postfemora and tibiae clearly incrassate, tarsi longest, slender, sphaerotrichomes missing (Figs 3A, B, 4B), claws simple, slightly curved (Fig. 4B, C); ♂ coxae 2 with short, membranous, cylindrical gonapophyses (Fig. 3G).

Gonopod aperture transversely oblong-oval, slightly subcordate, taking up most of ventral part of metazonite 7 (Fig. 4D). Gonopods (Fig. 4D–G) simple, with globose, scaly, medially fused coxae carrying a few setae on ventral face and a normal cannula mesally. Telopodites nearly straight, mostly exposed, in situ held parallel to each other, contiguous medially, largely unipartite due to prominent, rather densely setose prefemoral parts, rather short and stout, only distal quarter distinctly divided into a peculiar, axe-shaped, lateral solenophore (sph) and a smaller, anteriorly lying, sublanceolate solenomere (sl) directed slightly laterad. Seminal groove running entirely mesally, terminating on top of sl.

Holotype ♂ (MNHN JC 356), Vietnam, Kien Giang Province, Ha Tien, Nui Da Dung, valley, 104.477E, 10.4288N, secondary forest, litter, Berlese extraction, 29.11.2006, leg. L. Deharveng & A. Bedos (Vn06-102).

Paratypes: 1 ♂ (SEM), same locality, together with holotype; 1 ♂, 1 ♀ fragment (MNHN JC 356), 1 ♀ (SEM), same locality, soil, Berlese extraction, 05.12.2005, leg. L. Deharveng & A. Bedos (Vn05-107); 1 ♂ (ZMUM ρ2347), same locality, litter, Berlese extraction, 05.12.2005, leg. L. Deharveng & A. Bedos (Vn05-112).

To emphasize the particularly strong similarity to the previous new species.

Differs from all congeners, except Aporodesmella securiformis sp. n., in the presence of a peculiar, dorsoparabasal stump on ♂ antennomere 6, from Aporodesmella securiformis sp. n. in the shape of the solenophore and solenomere.

Length of adults ca 3.0 mm, width of midbody pro- and metazonae 0.2 and 0.25 mm (♂). Coloration in alcohol uniformly pallid, tegument nearly translucent.

Body moniliform, subcylindrical (Fig. 5A–J), with 19 segments (♂).

All characters as in Aporodesmella securiformis sp. n. (Figs 5, 6A), except as follows.

Gonopods (Fig. 6B, C) more complex, especially due to an elaborate and subtruncate tip of a more elongate and slenderer telopodite. Solenophore branch (sph) long, membranous, somewhat spoon-shaped, directed laterad, with a long, caudolateral, similarly membranous, subspiniform process (s) starting at base of sph and remaining coaxial with a prominent prefemoral portion. Mesal part of telopodite tip divided into 2 small horns (a and b) bearing a very small, dentiform solenomere (sl) lying in front and in between.

Holotype ♂ (MNHN JC 357), Vietnam, Kien Giang Province, Kien Luong, Hon Chong, Nui Bai Voi, cirque du Français, 104.618799E, 10.218541N, litter, Berlese extraction, 23.08.2003, leg. L. Deharveng & A. Bedos (Vn0308-112).

Paratypes: 1 ♂, 1 ♀ (SEM), same locality, together with holotype.

To emphasize the well-developed paraterga.

Differs from congeners by well developed paraterga, short tergal setae, the ♂ also by the presence of a peculiar, central hump above the antennae, the laterally bent, beak-shaped solenophore and the absence of a solenomere.

Length of adults ca 4.0 mm, width of midbody pro- and metazonae 0.4 and 0.5 mm (♂). Coloration in alcohol uniformly pallid, tegument nearly translucent.

Body with 19 segments (♂). Tegument dull, texture delicately alveolate, a cerategument on metazonae well-developed (Fig. 8A). Head with an evident, round, very finely pilose, central hump above antennae (♂) (Fig. 7D, G), more roughly setose over remaining surface except occiput; epicranial suture superficial; genae squarish (Fig. 7A, D, G); gnathochilarium narrow, setae on lamellae linguales particularly strong (Fig. 8B); isthmus between antennae about 1.5 times as broad as diameter of antennal socket (Fig. 7G). Antennae very short, reaching only behind collum when stretched dorsally, not geniculate, strongly clavate due to an abruptly and particularly enlarged antennomere 6, the latter with a usual, tight, distodorsal group of numerous bacilliform sensilla, antennomere 5 with a smaller, but also compact, distodorsal group of only a few shorter sensilla, 7^th with a tiny mid-dorsal knob (Fig. 7J).

In width, head = collum < segment 3 = 4 < 2 < 5 = 16 (♂), thereafter body gradually tapering towards telson (Fig. 7D–F). Paraterga well-developed, set low (at about upper 1/3-1/2 of body height), mostly clearly declined (Fig. 7A–F, K), front edges moderately convex and forming a shoulder, caudal edges increasingly strongly concave caudad, lateral edges mostly straight, on each side with 3 setigerous, equidistant knobs; caudal corners mostly nearly sharp, lying within rear tergal margin until segment 10, thereafter increasingly well produced behind the margin (Fig. 7A–F). Ozopores totally absent (Figs 7A–F, I, 8A). Collum biconvex, nearly sharp laterally on both sides, with 3 transverse rows of short setae (Fig. 7D). Each following metatergum mostly with 3+3 short, slightly blunted, clavate, thickened and longitudinally ribbed setae arranged in 3 transverse regular rows and borne on minute knobs; sulci between the rows absent (Figs 7A–F, M, 8A). Stricture between pro- and metazonae rather shallow and narrow, scaly like rear part of prozonae (Fig. 7E, L). Limbus very fine, very delicately and sparsely microdenticulate (Fig. 7L). Pleurosternal carinae absent (Fig. 7A, B, H). Epiproct short, conical, truncate, directed caudoventrally; pre-apical papillae large (Fig. 7C, F, I). Hypoproct subtrapeziform, caudal setigerous papillae well-developed and clearly separated (Fig. 7I).

Sterna without modifications, rather broad and sparsely setose. Legs short, ca 1.2–1.3 times as long as midbody height (♂); prefemora, femora, postfemora and tibiae clearly incrassate, tarsi longest, slender, sphaerotrichomes missing; claws simple, slightly curved (Fig. 7N); ♂ coxae 2 with very short, membranous, cylindrical gonapophyses (Fig. 7H).

Gonopod aperture transversely oblong-oval, slightly subcordate, taking up most of ventral part of metazonite 7 (Fig. 8C). Gonopods (Fig. 8C–F) rather complex, with globose, microgranulate, medially fused coxae carrying a few setae on ventral face and a normal cannula mesally. Telopodites mostly exposed, in situ held parallel to each other, nearly contiguous medially, each unipartite, with a rather large, densely setose prefemoral part clearly set off from acropodite by an oblique ventral sulcus and a curved dorsal spine (k); acropodite divided into 2 subequally long parts, each also about equal in length to prefemoral portion; basal half of acropodite remaining coaxial with prefemoral portion, slightly broadened distad and carrying an evident orifice (o) of a fully mesally running seminal groove on a vestigial mesal solenomere (= tubercle), whereas distal half of acropodite, or solenophore (sph), acuminate, directed abruptly laterad, subflagelliform (b), carrying a parabasal apical tooth (t) and a conspicuous, curved, denticulate lamina (a) beginning from near o and turning around b on lateral side.

This species served elsewhere (Golovatch et al. 2013) to illustrate a somewhat transitional condition in its gonopod structure, especially an elongate and laterad directed apical part, between the Trichopolydesmidae (= “Fuhrmannodesmidae”) and Opisotretidae within the same superfamily Trichopolydesmoidea. A far more spectacular example of the same trend is seen in Gonatodesmus gen. n. (see below).

18 segments (♂, ♀); pore formula normal: 5, 7, 9, 10, 12, 13, 15–17; head modified in both sexes in being somewhat flattened dorsoventrally; paraterga very poorly developed, serrate/microdentate at lateral edge, with 3 rows of 2+2, long, simple setae (regardless of lateral setae); gonopod coxae with gonocoel not deep; telopodites clearly exposed, but lying tightly appressed and parallel to venter, strongly curved, semi-circular, unipartite, slender, directed mesad and strongly overlapping; prefemoral parts about half as long as telopodites, set off from acropodites neither by a sulcus nor a cingulum; acropodites with small solenophores (sph) lying basal to a spiniform, apical solenomere (sl). Seminal groove running mostly along ventral surface of subbasally obviously twisted acropodites.

To honour Louis Deharveng (MNHN), one of the principal collectors, masculine.

Deharvengius bedosae sp. n., by present designation.

In having only 18 body segments, this new genus is almost unique amongst the Trichopolydesmoidea. The same segment counts seem to solely concern Moojenodesmus pumilus Schubart, 1944, only one of the species of the rather small Neotropical genus Moojenodesmus Schubart, 1945, from the same family Trichopolydesmidae; Moojenodesmus pumilus is especially minute (< 2.5 mm long), and it seems to be parthenogenetic and quite widespread in Brazil (Golovatch 1992, 1994). Among the Oriental Trichopolydesmidae, partly globally as well, Deharvengius gen. n. stands well apart also in having a less convex head, only 2+2 tergal setae per row and very unusual gonopods. The latter are long, simple, unipartite, strongly curved and crossing medially, thus being quite similar to the condition observed in Cocacolaria (Fig. 2B–E). Yet in Deharvengius gen. n. the gonopods are much more strongly appressed to the venter while the seminal groove runs mostly on the ventral = lateral (not mesal) side to terminate apically on a simple and slender (not at about midway on a stout and calyciform) solenomere. By its habitus and even gonopod structure, Deharvengius gen. n. resembles some Euro-Mediterranean genera of Trichopolydesmidae as well (see reviews by Mauriès (1983) and Golovatch et al. (2013)). Some of them show a deeply bipartite and strongly curved gonopod telopodite, the prefemoral part of which is quite elongate, but lies more or less transversely to strongly angular, largely (sub)parallel telopodites and extends across the nearly entire ventral width of segment 7. Such are Trichopolydesmus Verhoeff, 1898 (together with the subgenus Banatodesmus Tabacaru, 1980), Bacillidesmus Attems, 1898, Napocodesmus Ceuca, 1974 and Caucasodesmus Golovatch, 1985. In contrast, the gonotelopodites in Verhoeffodesmus Strasser, 1959, Cottodesmus Verhoeff, 1936 and Occitanocookia Mauriès, 1980 have increasingly shortened prefemoral parts, being enlarged and laterally flattened distad and unipartite, but mostly less strongly curved, in Cottodesmus and Occitanocookia also devoid of a solenomere, but sometimes supplied instead with what can be seen as a primordial accessory seminal chamber. In Trichopolydesmus, Heterocookia Silvestri, 1898, Ingurtidorgius Strasser, 1974 and, especially, Mastigonodesmus Silvestri, 1898, the solenomere is almost to fully flagelliform, branching off near the base of the femorite. In all these genera, the gonotelopodites are strongly exposed, not sunken inside an obvious gonocoel (Golovatch et al. 2013).

Deharvengius gen. n. currently contains only one species.

Holotype ♂ (MNHN JC 358), Vietnam, Kien Giang Province, Kien Luong, Hon Chong, Nui Bai Voi (cirque sud), 104.617E, 10.2199N, soil, Berlese extraction, 26.11.2008, leg. L. Deharveng & A. Bedos (Vn06-30).

Paratypes: 2 ♀, 4 juv. (subadults) (MNHN JC 358), same province, Kien Luong, Hon Chong, Nui Bai Voi (cirque sud), 104.617E, 10.2199N; soil, Berlese extraction, 02.06.2008, leg. L. Deharveng & A. Bedos (Vn08-055); 1 ♂, 2 ♀ (MNHN JC 358), 1 ♂ (ZMUM ρ2348), 1 ♂, 1 juv. (subadult) (SEM), same province, Hon Chong, Nui Khoe La, soil, Berlese extraction, 01.06.2008, leg. L. Deharveng & A. Bedos (Vn08-027).

To honour Anne Bedos (MNHN), one of the principal collectors.

Length of adults ca 3.0 mm, width of midbody pro- and metazonae 0.3 and 0.45 mm (♂, ♀). Coloration in alcohol uniformly pallid, tegument often nearly translucent.

Body with 18 segments (♂, ♀). Tegument dull, texture of metazonae very delicately punctate on dorsum and sterna, but alveolate laterally below paraterga; collum smooth (Fig. 9A–K). Head relatively sparsely and finely pilose, less convex than usual (♂, ♀); epicranial suture superficial; genae squarish (Fig. 9A, D, G, L); gnathochilarium narrow, sparsely and uniformly setose (Fig. 9L); isthmus between antennae about 0.8 times as broad as diameter of antennal socket (Fig. 9A, G). Antennae very short (Fig. 10A), reaching only behind head when stretched dorsally, not geniculate, strongly clavate due to an abruptly and particularly enlarged antennomere 6, the latter with a usual, tight, distodorsal group of rather numerous, bacilliform sensilla; antennomere 7 with a smaller distodorsal group of only a few shorter and curved sensilla in front of a tiny mid-dorsal knob.

Body moniliform, subcylindrical (Fig. 9A–J). In width, head > segments 5-15 > 2 > 3 = 4 > collum; body gradually tapering on segments 16-18 (Fig. 9A–I). Paraterga very poorly developed, starting from collum, set low (at about upper 1/3-1/2 of body height), mostly represented by vestigial, delicately serrate ridges and sharp caudal teeth, the latter being clearly enlarged and slightly produced behind rear tergal margin in poriferous segments (Fig. 9A–K). Ozopores evident, ovoid, dorsolateral, lying about equally close to caudal corner and lateral edge (Fig. 9B, C, E, F, K). Collum roundly subquadrate, with 3 transverse rows of long setae dorsally and 2 similar setae on paraterga (Fig. 9A). Each following metatergum mostly with 2+2 long and pointed setae arranged in 3 transverse regular rows and not borne on knobs; sulci between the rows absent (Fig. 9B–F). Stricture between pro- and metazonae rather deep and narrow, scaly like rear part of prozonae (Fig. 9B, E). Limbus very fine, very delicately and sparsely microdenticulate (Figs 9J, K, 10D). Pleurosternal carinae absent (Fig. 9D–F). Epiproct short, conical, truncate, directed caudoventrally; pre-apical papillae small (Fig. 9C, F, I). Hypoproct subtrapeziform, relatively high and narrow, caudal setigerous papillae large and moderately separated, with a faintly convex edge in between (Fig. 9I).

Sterna without modifications, rather broad and sparsely setose (Fig. 9G–I). Legs short, ca 1.2–1.3 (♂) or 1.0–1.1 (♀) times as long as midbody height; prefemora, femora, postfemora and tibiae clearly incrassate, especially so in ♂ (Fig. 10B), tarsi longest, slender, sphaerotrichomes missing; claws simple, slightly curved; ♂ coxae 2 with very short, membranous, cylindrical gonapophyses (Fig. 9G).

Gonopod aperture transversely oblong-oval, taking up most of ventral part of metazonite 7 (Fig. 10C–E). Gonopod coxae with gonocoel not deep; telopodites clearly exposed, but lying tightly appressed and parallel to venter, strongly curved, semi-circular, unipartite, slender, directed mesad and strongly overlapping; prefemoral parts about half as long as telopodites, set off from acropodites neither by a sulcus nor a cingulum; each acropodite with a small solenophore (sph) lying basal to a spiniform, apical solenomere (sl). Seminal groove running mostly along ventral (= lateral) surface of a subbasally obviously twisted acropodite.

19 segments (♂, ♀); pore formula normal: 5, 7, 9, 10, 12, 13, 15-18; ♂ head with a considerable, rounded, central hump above antennae; paraterga poorly developed, serrate/microdentate at lateral edge, with 3 rows of 3+3 or 4+4, long, bacilliform setae (regardless of lateral setae); gonopod coxae with gonocoel not deep; telopodites clearly exposed, but lying rather tightly appressed and mostly parallel to venter, unipartite, slender, abruptly geniculate and directed laterad distal to prefemoral parts, the latter about half as long as telopodites, held parallel to main axis, each set off from a twisted acropodite by a geniculation cingulum (c); acropodites elongate, near midway with a remarkably large hairy pulvillus (p) on top of a small accessory seminal chamber; neither a separate solenophore branch nor a solenomere. Seminal groove (sg) running mostly on mesal side, turning caudad (= ventrad) only beyond geniculation.

To emphasize the geniculated gonopod telopodite (γόνατο meaning “a knee” in Greek), masculine.

Gonatodesmus communicans sp. n., by present designation.

This new genus is highly disjunct in being the sole member of the family which shows a remarkable midway geniculation of the gonopod telopodite. The gonopod tip being directed laterad is not unique in Trichopolydesmidae, shared also with Aporodesmella tergalis sp. n. However, the entire distal, post-geniculation half of the gonopod in Gonatodesmus gen. n. is obviously twisted and strongly elongate, also showing a remarkably distinct hairy pulvillus on top of a small, but evident accessory seminal chamber. Only vestiges of the latter are occasionally observed in a couple of Euro-Mediterranean genera of Trichopolydesmidae (Golovatch 2013), whereas an obvious hairy pulvillus seems to be singular in the family. In contrast, such a gonopod conformation vividly resembles the conditions largely characterizing the family Opisotretidae (Golovatch et al. 2013), but the prefemoral parts in Gonatodesmus gen. n. are clearly elongate and held parallel to the main axis while the acropodites distal to the unique geniculation are yet relatively short to be directed dorsolaterad. So the assignment of Gonatodesmus gen. n. to Trichopolydesmidae, not Opisotretidae, is preferred. However, one may justly regard Gonatodesmus gen. n. as a kind of transition or bridge between these two families of Trichopolydesmoidea. This new genus rather demonstrates an evolutionary trend from the more basal Trichopolydesmidae towards the advanced Opisotretidae.

Holotype ♂ (MNHN JC 359), Vietnam, Dongnai Prov., Cat Tien National Park, 107°10'–107°34'E, 11°21'–11°48'N, lowland tropical forest, litter and topsoil, 01.06.2005, leg. A. Anichkin.

Paratypes: 5 ♂, 1 ♀ (MNHN JC 359), 9 ♂, 1 ♀, 1 juv. (ZMUM ρ2336–2339), 1 ♂ (SEM), 1 ♂ (ZMUC), same locality, together with holotype; 1 ♀ (MNHN JC 359), same locality, 15.07.2005, leg. A. Anichkin.

The species epithet refers to the gonopod conformation somewhat transitional between the families Trichopolydesmidae and Opisotretidae.

Length of adults ca 2.8-3.7 mm, width of midbody pro- and metazonae 0.2–0.25 and 0.28–0.4 mm (♂, ♀). Coloration in alcohol uniformly pallid, tegument often nearly translucent.

Body with 19 segments (♂, ♀). Tegument dull, texture of pro- and metazonae delicately alveolate to scaly, metaterga a little more roughly alveolate, only sterna mostly smooth (Fig. 11A–I). Head very densely and finely pilose; epicranial suture absent (♂) or superficial (♀); genae squarish (Fig. 11A, D, G, K); gnathochilarium narrow, sparsely and uniformly setose (Fig. 11K); isthmus between antennae about 1.2 times as broad as diameter of antennal socket (Fig. 11G). Antennae short (Figs 11A, G, 12A), reaching only behind collum when stretched dorsally, not geniculate, rather strongly clavate due to a particularly enlarged antennomere 6, the latter with a usual, tight, distodorsal group of numerous, bacilliform sensilla; a similar, but smaller, also distodorsal group of sensilla on antennomere 5; antennomere 7 with a smaller distodorsal group of only a few shorter and curved sensilla in front of a tiny mid-dorsal knob.

In width, collum < segment 3 = 4 < 2 = 5 < 6–15 < head; body gradually tapering on segments 16–18 (Fig. 11A–I). Paraterga poorly developed, starting from collum, set rather low (at about upper 1/3 of body height, Fig. 11J), at most small ridges with 2–3 lateral, setigerous knobs, caudal corner never produced behind rear tergal margin even in poriferous segments (Fig. 11A–F, N). Ozopores evident, ovoid, dorsolateral, mostly lying closer to lateral edge, but in segments 15-18 slightly elevated and positioned closer to caudal edge between 2 subequal, setigerous stalks (Fig. 11N). Collum regularly rounded, transversely oblong-oval, with 3 transverse rows of 4+4, 2+2 and 3+3 rather long setae dorsally and 2 similar setae on paraterga (Fig. 11A, D). Each following metatergum with 3+3 or 4+4, similarly long, bacilliform, delicately ribbed setae arranged in 3 transverse regular rows and borne on knobs; sulci between the rows absent (Fig. 11A–F, L–N). Stricture between pro- and metazonae rather deep and narrow, microalveolate like metazonae (Fig. 11E, L, N). Limbus very fine, delicately and densely microcrenulate (Fig. 11E, N). Pleurosternal carinae absent (Fig. 11A–C). Epiproct short, conical, truncate, directed caudoventrally; pre-apical papillae very small (Fig. 11C, F). Hypoproct subtrapeziform, caudal setigerous papillae large and well separated, with a faintly convex edge in between (Fig. 11I).

Sterna without modifications, rather broad and sparsely setose (Fig. 11H, I). Legs short and stout, ca 1.2–1.3 (♂) or 1.0–1.1 (♀) times as long as midbody height; prefemora, femora, postfemora and tibiae clearly incrassate, especially so in ♂ (Fig. 12C), tarsi longest, slender, sphaerotrichomes missing; claws simple, slightly curved; ♂ tarsi 1 with peculiar, bi- or trifid setae ventrally (Fig. 12B); ♂ coxae 2 with very short, membranous, cylindrical gonapophyses (Fig. 11G).

Gonopod aperture transversely oblong-oval, taking up most of ventral part of metazonite 7 (Fig. 12D). Gonopod coxae (Fig. 12D–G) rather small (gonocoel not deep), sparsely setose and clearly micropapillate laterally, each with a subtriangular ventral projection (x); telopodites clearly exposed, but lying rather tightly appressed and parallel to venter, unipartite, slender, abruptly geniculate and directed laterad distal to prefemoral parts, the latter about half as long as telopodites, held parallel to main axis, each with an apicomedian field of strong curved spines (d), set off from a twisted acropodite by a strong geniculation cingulum (c); acropodite elongate, near midway with a remarkably large hairy pulvillus (p) on top of a small accessory seminal chamber; acropodite distal to pulvillus particularly slender, slightly curved caudad, subacuminate; neither a separate solenophore branch nor a solenomere. Seminal groove (sg) running mostly on mesal side, turning caudad (= ventrad) only beyond geniculation.

19 segments (♂, ♀); pore formula normal: 5, 7, 9, 10, 12, 13, 15–18; head without modifications; paraterga poorly developed, metaterga with 3 rows of 3+3 or, more rarely, 4+4, long, bacilliform setae (regardless of lateral setae); gonopod coxae with gonocoel not deep; telopodites rather clearly exposed and transverse, but stout and remarkably complex, very strongly twisted, partly fimbriate/plumose distally, with several outgrowths of varying shapes; prefemoral part about half the height of telopodite, demarcated on lateral (not medial!) side by an oblique seminal groove running further mesad onto a medioventral outgrowth of acropodite to terminate distally, with neither a solenomere nor an accessory seminal chamber, nor a pulvillus.

To emphasize the strongly helicoid gonopod telopodite, masculine.

Helicodesmus anichkini sp. n., by present designation.

This new genus is remarkable within Trichopolydesmidae in showing particularly strongly twisted gonopods, including their prefemoral parts, such that the seminal groove turns ca 180° around the highly complex transverse acropodite. Also noteworthy is the complete lack of a solenomere.

Holotype ♂ (MNHN JC 360), Vietnam, Dongnai Prov., Cat Tien National Park, 107°10'–107°34'E, 11°21'–11°48'N, lowland tropical forest, litter and topsoil, 01.06.2005, leg. A. Anichkin.

Paratypes: 2 ♂, 1 ♀ (ZMUM ρ2340, ρ2343), 1 ♂ (SEM), same locality, together with holotype; 1 ♂ (ZMUM ρ2342), same locality, 01.04.2005; 2 ♂ (MNHN JC 360), 1 ♂ (ZMUM ρ2341), same locality, 15.07.2005; 1 ♂, 1 ♀ (MNHN JC 360), 2 ♂ (ZMUM ρ2344, ρ2345), same locality, 23.11.2005; 1 ♂ (MNHN JC 360), same locality, 17.07.2005; 1 ♂ (ZMUC), same locality, 15.05.2005, all leg. A. Anichkin.

To honour Alexander E. Anichkin, who provided for study all millipede material he had collected in Cat Tien National Park, including three trichopolydesmids described here.

Length of adults ca 3.0-4.0 mm, width of midbody pro- and metazonae 0.28-0.32 and 0.4-0.45 mm (♂, ♀). Coloration in alcohol uniformly pallid, tegument often nearly translucent.

Body with 19 segments (♂, ♀). Tegument dull, texture of nearly entire body delicately alveolate to scaly, only sterna nearly smooth (Fig. 13A–I). Head very densely and finely pilose; epicranial suture highly superficial; genae squarish (Fig. 13A, D, G, K); gnathochilarium rather broad, sparsely and uniformly setose (Fig. 13K); isthmus between antennae about 1.2–1.3 times as broad as diameter of antennal socket (Fig. 13G, K). Antennae short (Fig. 13A, D, G), reaching only behind collum when stretched dorsally, not geniculate, rather strongly clavate due to a particularly enlarged antennomere 6, the latter with a usual, tight, distodorsal group of numerous, bacilliform sensilla; a similar, but smaller, also distodorsal group of sensilla on antennomere 5; antennomere 7 with a smaller distodorsal group of only a few shorter and curved sensilla in front of a tiny mid-dorsal knob.

In width, collum = segment 3 = 4 < 5 < 2 < 6–15 < head; body gradually tapering on segments 16-18 (Fig. 13D–F). Paraterga mostly moderately wide, starting from collum, set rather low (at about upper 1/3 of body height, Fig. 13J), at most small ridges with 2-3 lateral, setigerous knobs, absent from segment 18, caudal corner never produced behind rear tergal margin even in poriferous segments (Fig. 13A–G, M). Ozopores evident, ovoid, dorsolateral, mostly lying closer to lateral edge (Fig. 13M). Collum biconvex, sides (= paraterga) narrowly rounded, dorsal surface with 3 transverse rows of 5+5, 3+3 and 4+4 rather long setae dorsally and 2 similar setae on paraterga (Fig. 13A, D). Each following metatergum with 3+3 or, more rarely, 4+4, similarly long, bacilliform, delicately ribbed setae arranged in 3 transverse regular rows and borne on knobs; sulci between the rows absent (Fig. 13A–G, L, M). Stricture between pro- and metazonae rather deep and narrow, microalveolate like adjacent metazonae (Fig. 13E, L). Limbus very fine, delicately and densely microcrenulate (Fig. 13L, M). Pleurosternal carinae absent (Fig. 13A–C). Epiproct short, conical, truncate, directed caudoventrally; pre-apical papillae evident (Fig. 13C, F, I). Hypoproct subtrapeziform, caudal setigerous papillae moderate and well separated (Fig. 13I).

Sterna without modifications, rather broad and sparsely setose (Fig. 13G, H). Legs short and stout, ca 1.1–1.2 (♂) or 0.9–1.0 (♀) times as long as midbody height; prefemora, femora, postfemora and tibiae clearly incrassate, especially so in ♂ (Fig. 13N), tarsi longest, slender, sphaerotrichomes missing; claws simple, slightly curved; ♂ coxae 2 with very short, membranous, cylindrical gonapophyses (Fig. 13G).

Gonopod aperture transversely oblong-oval, taking up most of ventral part of metazonite 7 (Fig. 14A). Gonopod coxae rather small (gonocoel not deep), sparsely setose and clearly micropapillate laterally (Figs 14, 15); telopodites quite well exposed and unusually transverse, but stout and remarkably complex, very strongly twisted, partly fimbriate(curved ventral projections c1 and c2) or plumose (a long lateral process k), with several outgrowths of varying shapes (a stump-shaped, rounded, mesal i and 2 indistinctly separated, densely microdentate, also rounded m and l); prefemoral part about half the height of telopodite, demarcated on lateral (not medial!) side by an oblique seminal groove running further mesad onto a medioventral outgrowth of acropodite to terminate distally at joint base of c1 and c2, with neither a solenomere nor an accessory seminal chamber, nor a pulvillus.

19 segments (♂), ♀ unknown; pore formula normal: 5, 7, 9, 10, 12, 13, 15–18; head without modifications; paraterga poorly developed, metaterga with 3 rows of 3+3 or, more rarely, 4+4, long, bacilliform setae (regardless of lateral setae); gonopod coxae large (gonocoel quite deep); telopodites rather well exposed, tripartite, without evidence of torsion, elongate, moderately curved caudad, subcontiguous medially and held parallel to each other; acropodites lying distal to prefemoral parts much longer than and coaxial with the latter; solenomere (sl), or endomere, a strong, simple, frontal branch about as long as a lateral exomere (ex); a very long, flagelliform, mesal branch (fl) at base of both sl and ex; seminal groove (sg) running entirely along mesal side of sl to terminate on top with neither an accessory seminal chamber nor a pulvillus.

To emphasize the monstrously long flagellum of the gonopod, masculine.

Monstrodesmus flagellifer sp. n., by present designation.

This new genus seems to be particularly similar to Topalodesmus Golovatch, 1988, monobasic, from the Himalayas of India (Golovatch 1988b). Indeed, both share basically the same gonopod conformation: coxae quite massive; gonocel rather deep, but telopodites clearly exposed, deeply tripartite, untwisted, curved caudad, subcontiguous medially and held parallel to main axis; seminal groove running entirely mesally along a very strong frontal endomere branch (= solenomere, sl). However, the differences are definitely significant enough to keep these two genera separate. Unlike Topalodesmus which shows 20 segments in both sexes, the gonopod coxa in Monstrodesmus gen. n. is devoid of a frontal process, the exomere (ex) prominent (vs vestigial), the caudomesal branch (fl) unusually long and flagelliform (vs thick and unciform) while the solenomere (sl) a very long, strong, frontal branch.

Holotype ♂ (MNHN JC 361), Vietnam, Dongnai Prov., Cat Tien National Park, 107°10'–107°34'E, 11°21'–11°48'N, lowland tropical forest, litter and topsoil, 01.06.2005, leg. A. Anichkin.

Paratype: 1 ♂ (SEM), same locality, together with holotype.

The species epithet, a noun in apposition, is to emphasize the remarkably long gonopod flagellum.

Length of adults ca 4.5 mm, width of midbody pro- and metazonae 0.33 and 0.4 mm (♂). Coloration in alcohol uniformly pallid, tegument often nearly translucent.

Body with 19 segments (♂). Tegument dull, texture of nearly entire body delicately alveolate to scaly, only sterna nearly smooth (Fig. 16A–I). Head very densely and finely pilose; epicranial suture highly superficial; genae squarish (Fig. 16A, D, G); gnathochilarium rather broad, sparsely and uniformly setose (Fig. 16K); isthmus between antennae about 1.2 times as broad as diameter of antennal socket (Fig. 16G). Antennae short (Fig. 16G, L), reaching only behind collum when stretched dorsally, not geniculate, rather strongly clavate due to a particularly enlarged antennomere 6, the latter with a usual, tight, distodorsal group of numerous, bacilliform sensilla; a similar, but smaller, also distodorsal group of sensilla on antennomere 5; antennomere 7 with a smaller distodorsal group of only a few shorter and curved sensilla in front of a tiny mid-dorsal knob.

In width, collum < segment 3 = 4 < head = 2 < 5-15; thereafter body gradually tapering (Fig. 16D–F). Paraterga mostly moderate, starting from collum, set rather low (at about upper 1/3 of body height, Fig. 16J), at most small ridges with 2-3 lateral, setigerous knobs, absent from segment 18, caudal corner never produced behind rear tergal margin even in poriferous segments (Fig. 16A–I, O). Ozopores evident, ovoid, dorsolateral, mostly lying closer to lateral edge (Fig. 16B, C, E, F, O). Collum subovoid, sides (= paraterga) well rounded, dorsal surface with 3 transverse rows of 4+4, 3+3 and 3+3 rather long setae dorsally and 2 similar setae on paraterga (Fig. 16A, D). Each following metatergum with 3+3 or, more rarely, 4+4, similarly long, bacilliform, delicately ribbed setae arranged in 3 transverse regular rows and borne on knobs; sulci between the rows superficial (Fig. 16A–F). Stricture between pro- and metazonae rather deep and narrow, microalveolate like adjacent metazonae (Fig. 16A–F, M, O). Limbus very fine, delicately and densely microspiculate (Fig. 16M, O). Pleurosternal carinae absent (Fig. 16A–C). Epiproct short, conical, truncate, directed caudoventrally; pre-apical papillae small (Fig. 16C, F, I). Hypoproct subtrapeziform, caudal setigerous papillae moderate and well separated (Fig. 16I).

Sterna without modifications, rather broad and sparsely setose (Fig. 16H, I). Legs short and stout, ca 1.1-1.2 times as long as midbody height (♂); prefemora, femora, postfemora and tibiae clearly incrassate (Fig. 17A), tarsi longest, slender, sphaerotrichomes missing; claws simple, slightly curved (Fig. 17B); coxae 2 with very short, membranous, cylindrical gonapophyses.

Gonopod aperture transversely obcordate, taking up most of ventral part of metazonite 7 (Fig. 17C, E). Gonopod coxae large (gonocoel rather deep), with 2 long setae and clearly micropapillate laterally, but without any frontal outgrowths (Fig. 17C–G, 18); telopodites quite well exposed, not twisted, tripartite, elongate, moderately curved caudad, subcontiguous medially and held parallel to each other; acropodites lying distal to prefemoral parts much longer than and coaxial with the latter; solenomere (sl) (= endomere) a strong, simple, frontal branch about as long as an apically bifid lateral exomere (ex); an extremely long, flagelliform, mesal branch (fl) at base of both sl and ex; seminal groove (sg) running entirely along mesal side of sl to terminate on top with neither an accessory seminal chamber nor a pulvillus.