Revision of the Southeast Asian millipede genus Orthomorpha Bollman, 1893, with the proposal of a new genus (Diplopoda, Polydesmida, Paradoxosomatidae)

Abstract The large genus Orthomorpha is rediagnosed and is shown to currently comprise 51 identifiable species ranging from northern Myanmar and Thailand in the Northwest to Lombok Island, Indonesia in the Southeast. Of them, 20 species have been revised and/or abundantly illustrated, based on a restudy of mostly type material; further 12 species are described as new: Orthomorpha atypica sp. n., Orthomorpha communis sp. n., Orthomorpha isarankurai sp. n., Orthomorpha picturata sp. n., Orthomorpha similanensis sp. n., Orthomorpha suberecta sp. n., Orthomorpha tuberculifera sp. n.,Orthomorpha subtuberculifera sp. n. and Orthomorpha latiterga sp. n., all from Thailand, as well as Orthomorpha elevata sp. n.,Orthomorpha spiniformis sp. n. and Orthomorpha subelevata sp. n., from northern Malaysia. The type-species Orthomorpha beaumontii (Le Guillou, 1841) is redescribed in due detail from male material as well, actually being a senior subjective synonym of Orthomorpha spinala (Attems, 1932), syn. n. Two additional new synonymies are proposed: Orthomorpha rotundicollis (Attems, 1937) = Orthomorpha tuberculata (Attems, 1937), syn. n., and Orthomorpha butteli Carl, 1922 = Orthomorpha consocius Chamberlin, 1945, syn. n., the valid names to the left. All species have been keyed and all new and some especially widespread species have been mapped. Further six species, including two revised from type material, are still to be considered dubious, mostly because their paraterga appear to be too narrow to represent Orthomorpha species. A new genus, Orthomorphoides gen. n., diagnosed versus Orthomorpha through only moderately well developed paraterga, coupled with a poorly bi- or trifid gonopod tip, with at least some of its apical prongs being short spines, is erected for two species: Orthomorpha setosus (Attems, 1937), the type-species, which is also revised from type material, and Orthomorpha exaratus (Attems, 1953), both comb. n. ex Orthomorpha.

to correlate with one another, but also vary too considerably, no longer allowing for a clear-cut distinction between the species groups to be made. The abundant material (re)studied for this project shows all possible transitions, merging and blurring the borders between such groups. Instead, we can only outline certain trends in the development of the above and some other basic structures.
Unlike most of the genera of Polydesmida, including Paradoxosomatidae, Orthomorpha has long been acknowledged as a group showing surprisingly uniform gonopods (Jeekel 1963). Whereas species of most of the paradoxosomatid genera are rich in gonopod characters, e.g. Tylopus Jeekel, 1968 (tribe Sulciferini) (Likhitrakarn et al. 2010b), with somatic features often being rather subordinate, Orthomorpha species usually present only a few or no meaningful traits for their separation. Instead, the peripheral structures such as tegument texture, paraterga, pleurosternal carinae etc. show a remarkably wide range of variation. Sometimes broad variation in somatic characters is observed not only between species, but infraspecifically as well, as demonstrated for O. insularis by Jeekel (1970) or for O. enghoffi Likhitrakarn, Golovatch & Panha, 2010 by Likhitrakarn et al. (2010a).
So we are inclined to abandon species group delimitation in Orthomorpha altogether. Instead, we arrange the species mainly on the structure of the gonopod tip, however few characters it offers. This approach better agrees with Jeekel (1963Jeekel ( , 1964, who put special emphasis on gonopod conformation, than with Hoffman (1977), who mostly relied on the structure of the sternal lobe or cones, if any, between ♂ coxae 4 when grouping species. Here we prefer to regard Orthomorpha as a member of the tribe Orthomorphini perhaps especially similar to the largely sympatric genus Antheromorpha Jeekel, 1968, which normally shows similarly large size and paraterga, but a very deeply bifid gonopod tip (see also below). In Orthomorpha, the latter is always poorly bi-or trifid, some of the apical prongs being either minute denticles, or rounded lappets, or small teeth, or completely reduced. Variations are few, but, together with certain peripheral characters, they generally offer enough grounds for a reliable discrimination of species.
Orthomorpha is the type genus of the tribe Orthomorphini, which has rather recently been reviewed and shown to currently contain 19 genera, nearly all of them keyed (Golovatch 1997a(Golovatch , 2000(Golovatch , 2009.
Because an analysis of the phylogeny of either Orthomorpha or Orthomorphini has never been attempted, below we arrange the species of Orthomorpha, according to the degree of gonopod tip complexity. The former coarctata-group, with only two constituent nominate species or subspecies, shows the tip bearing only a single terminal lappet. For this reason, O. coarctata (De Saussure, 1860), the only pantropical representative of Orthomorpha, has often been referred to as a distinct genus, Asiomorpha Verhoeff, 1939(e.g. Hoffman 1980Korsós 2004;Enghoff 2005). Yet, following Jeekel (1963Jeekel ( , 1968Jeekel ( , 1970, we prefer to regard O. coarctata as a species of Orthomorpha. Several further congeners that demonstrate a bifid tip will be treated next, followed by those, in which the tip is trifid. However, because the identity of the type-species has heretofore remained obscure, the taxonomic part below will start with a diagnosis of Orthomorpha, followed by a solution of the problem concerning O. beaumontii.
Most of the older species revised, especially those valid ones in which the original descriptions appear to be deficient, are redescribed and illustrated here in sufficient detail to ensure their easy recognition. ly) and elongate femorite devoid both of torsion (= the seminal groove running entirely or nearly entirely on the mesal side) and processes/outgrowths. A distolateral sulcus demarcating a "postfemoral" part is usually, but not always, present. A solenomere is always long and flagelliform, starting on top of the femorite (+ "postfemoral" part, if any) at the base of a more or less elaborate solenophore, the latter being demarcated by an evident cingulum or mesal sulcus. The solenophore always consists of well-to moderately well developed, often subequal, lamellar lamina lateralis and lamina medialis, both only modestly curved mesad or caudomesad and both supporting and sheathing at least most of the solenomere. It is the solenophore that provides most of the generic characters in Orthomorphini, such as the presence or absence of additional structures (processes or lobes) at its base, near midway and/or at its tip (Jeekel 1968;Golovatch 1997aGolovatch , 2000Golovatch , 2009. Orthomorpha is basically characterized by very broad paraterga, coupled with the gonopod showing mostly an elongate, slender femorite (+ "postfemoral" part, if any) and a long, modestly curved solenophore bearing additional structures neither at its midway nor near its base; the tip of the solenophore is never deeply split, normally poorly bi-or trifid, some of the apical prongs being either minute denticles or lappets, or small teeth, or completely reduced.
Based on the broad paraterga and the conformation of the solenophore, Orthomorpha comes closest to the continental Southeast Asian Antheromorpha Jeekel, 1968 (see above), the Philippine Luzonomorpha Hoffman, 1973 and the basically Bornean Gigantomorpha Jeekel, 1963(Jeekel 1963, 1980aHoffman 1973;Golovatch , 1997a. However, Antheromorpha species show a very deeply split tip of the solenophore, Gigantomorpha species demonstrate a somewhat flattened and bisinuate gonofemorite, usually also a more elaborate, often deeply split solenophore tip, whereas in Luzonomorpha the tip is deeply bispinose. A similarly poorly bi-or trifid gonopod is only observed in Orthomorphoides gen. n., but its species differ from Orthomorpha in much smaller bodies, in the rather poorly developed paraterga and at least in some of the apical prongs of the solenophore being short spines (see below).  Attems, 1932. A, B, J anterior part of body, dorsal, lateral and dorsal views, respectively C, D, K segments 10 and 11, dorsal, lateral and dorsal views, respectively e-G, l posterior part of body, lateral, dorsal, ventral and dorsal views, respectively h, i sternal cones between coxae 4, subcaudal and sublateral views, respectively. tively. Coloration of alcohol material upon long-term preservation rather uniformly brown with contrasting pale yellowish paraterga, venter and legs light yellow-brown (Fig. 2).
Remarks. A complete historical review of the typification of Orthomorpha has long been provided by Jeekel (1963). Despite some confusion, Orthomorpha was properly typified by Pocock (1909), with O. beaumontii (Le Guillou, 1841 serving as the typespecies. Originally described as a subspecies of O. hydrobiologica (see Attems 1932), not as a variety as mistakenly quoted by Jeekel (1968), spinala has since been treated as a full species (Jeekel 1968). The above samples, especially the only available ♀ syntype, agree in almost every detail with the very accurate redescription of the O. beaumontii holotype provided by Jeekel (1963), making a restudy of the holotype superfluous. The few differences, such as size (4.4 vs 5.0 mm), coloration (brown vs blackish), the shape of the caudal tooth on pleurosternal carinae (sharp teeth vs triangular lappets), the presence of an anterolateral denticle on paraterga (very small vs virtually missing) etc., are deemed too minor, rather reflecting individual or population-level variation, to consider O. spinala as being distinct from O. beaumontii at the species level. Hence the new synonymy advanced. In addition, the type series of O. spinala derives from an islet lying nearly halfway between Java and the beaumontii type locality, Borneo. Jeekel (1963), when trying to find the closest match among the known Orthomorpha species to the holotype of O. beaumontii, emphasized its especially strong similarities to O. weberi. Slight differences were only noted in the shape of the paraterga. It was this that allowed Jeekel to unequivocally conserve the concept of Orthomorpha. Zoogeographically, the strong morphological similarities between O. beaumontii and O. weberi make sense, because the latter species is endemic to Java, Indonesia.
With the above synonymization, the nomenclature of Orthomorpha becomes stabilized, confirming this genus' present scope. The identity of its type-species, O. beaumontii, has been refined, based on male characters as well. Bollman (1893), when proposing Orthomorpha as a replacement name for the preoccupied Paradesmus De Saussure, 1859, synonymized O. beaumontii with O. spectabilis (Karsch, 1881, the latter species from Java. Apparently because he provided no evidence whatsoever to substantiate his synonymization, it has since been neglected, spectabilis still remaining a dubious name (e.g. Attems 1937;Jeekel 1968). Attems (1898Attems ( , 1914Attems ( , 1937 referred to beaumontii a sample from Java, Indonesia which he had received from the Berlin Museum, thus providing a second record of this species. However, because the gonopod tip of that sample shows a remarkably small subterminal lappet, while the paraterga and pleurosternal carinae slightly differ in shape from those of beaumontii, there can be no doubt of Attems' misidentification. Hence our references to it as such in the catalogue section above.    Gonopods (Figs 5,6 & 8) with tip of solenophore produced into a single lobe, all other spikes or denticles being either missing or nearly missing.

Species with only a single terminal lobule on the gonopod tip
Remarks. This pantropical species has been described and redescribed several times, often under different names (e.g. Jeekel 1968). From Thailand, it had been described as Paradesmus flavocarinatus until Enghoff (2005) showed it to actually represent still another synonym of O. coarctata. No full catalogue is attempted here as being superfluous, with hundreds of references involved.
Remarks. This species is only known from southern Vietnam (Dalat and Peak Lang Biang).
Remarks. Among all nine islets of the Similan Archipelago, Thailand inspected for millipedes in April 2010, only three appeared to support Orthomorpha species, one each per islet. Only O. picturata occurred on Ko Bangu, Island 9 (Map 2), another new species (O. similanensis sp. n., see below) on Ko Miang, Island 4, while Ko Huyong, Island 1 harboured still another presumed congener which regrettably cannot be described, because we only obtained female material.

Orthomorpha tuberculifera sp. n., variety from Khao Wong Phrachan Temple
All other characters as in the typical O. tuberculifera sp. n. , except as follows.  Venter and legs sometimes as pallid as paraterga and epiproct. Paraterga slightly less prominent, narrower (Fig. 16A,C & F). Pattern of setigerous tubercles in caudal row on metatergum 17 sometimes as 4+3, on metatergum 18 as 4+4. Paraterga 2 sometimes with four small indentations on one side, with three ones on the other. Surface below paraterga microgranulate and faintly rugulose.
All other characters as in the typical O. tuberculifera sp. n. , except as follows.
Paraterga less prominent, even midbody ones nearly not produced behind tergal margin   . Pattern of setigerous tubercles in caudal row on metatergum 19 sometimes as 4+3.  Name. To emphasize the strong similarity to O. tuberculifera sp. n. Diagnosis. Comes closest to O. tuberculifera sp. n., but differs in a strong anterolateral incision on paraterga (see also Key below).
Remarks. This new species has been found rather close to the localities of O. tuberculifera sp. n., but northeast of the Sankamphaeng Mountain Range, Khao Yai National Park (Map 2).   Name. To emphasize this species being quite common in the eastern part of Thailand close to the border with Cambodia.
Diagnosis. Differs in unequal terminal lobes of the solenophore, both of which show a minute tooth near their bases, coupled with pointed, subtriangular paraterga on the collum etc. (see also Key below).
Coloration of live animals (Fig. 25A) blackish-brown, paraterga and epiproct contrasting creamy yellow, antennae dark brown, legs brownish; coloration of alcohol material after preservation  uniformly blackish-brown with contrasting light yellowish-brown paraterga and epiproct, tip of antennae pallid, venter and basal 3-4 podomeres brown to grey-brown.
Gonopods (Figs 26 & 27) simple. Coxa long and slender, with numerous strong setae distodorsally and distolaterally. Prefemur densely setose, nearly 3 times shorter than femorite + "postfemoral" part. Femorite slender, slightly curved and not enlarged distad, with a "postfemoral" part demarcated by an oblique lateral sulcus. Solenophore with a bidentate tip, terminal denticle a little larger than subterminal one, both being supplied with an extremely small indentation near base; solenomere long and flagelliform.
Name. To emphasize this species being not quite typical to readily fit into any of the former species groups.
Diagnosis. Superficially, this new species strongly resembles O. communis sp. n., especially as regards the color pattern, the degree of development of some paraterga, and size. Yet the two species differ markedly in the development in O. atypica sp. n. of distinct sternal cones between ♂ coxae 4, coupled with a peculiar denticle placed on top of the outer lobule of the solenophore, not between the two terminal lobules characteristic of other species (see also Key below).
Gonopods (Figs 29,30) simple. Coxa long and slender, with several strong setae distodorsally. Prefemur densely setose, less than half the length of femorite + "postfemoral" part. Femorite slender, slightly curved and nearly not enlarged distad, with a "postfemoral" part demarcated by an oblique lateral sulcus. Solenophore with a bidentate tip, both prongs being subequal, but terminal lobule with an unusual minute denticle near base; solenomere long and flagelliform. Name. To emphasize the extremely broad paraterga. Diagnosis. Differs in the extremely broad paraterga, coupled with the pleurosternal carinae represented by complete high crests with a sharp caudal tooth on segments 2-7 (♂) etc. (see also Key below).
Live coloration (Fig. 31A) black-brown with mainly grey-brownish caudal halves of metaterga and bases of paraterga, and contrasting creamy light orange paraterga and epiproct; antennae blackish, legs light brown; coloration of alcohol material after preservation  rather uniformly dark brown with lighter caudal halves of metaterga and bases of paraterga, and contrasting pallid paraterga, epiproct and tip of antennae, legs brown to light grey-yellow.
Sterna sparsely setose, without modifications; cross-impressions shallow; lobe between ♂ coxae 4 much like in O. atypica sp. n., but cones more acute (Fig. 31I & J). A paramedian pair of small, but evident tubercles in front of gonopod aperture. Legs moderately long and slender, midbody ones ca 1.2-1.3 as long as body height, prefemora without modifications, ♂ tarsal brushes present only on legs 1-5.
Remarks. This new species shows the paraterga relatively perhaps among the broadest amongst congeners.
Coloration of alcohol material after long-term preservation castaneous brown with a pattern of contrasting whitish to light brown paraterga and epiproct, and mostly greyish-white to light brownish posterior halves of postcollum metaterga, with caudal edges and front 1/4 of metaterga, as well as surface below paraterga and entire rear halves of prozona brown to dark brown; head and antennomeres 6 and 7 brown to dark brown; venter and a few basal podomeres light brownish to brown, legs growing infuscate (brown) distally .
Remarks. This species was originally described in two varieties, each based on a single male: O. hydrobiologica var. hydrobiologica, from the shores of Lake Bedali, eastern Java, and O. hydrobiologica var. unicolor, from Sarangan, central Java, Indonesia (Attems 1930a). The holotype of O. hydrobiologica var. hydrobiologica has been redescribed above, also including some more non-type samples identified as such by Attems himself. As regards O. hydrobiologica var. unicolor, it proves to be a distinct species, likewise redescribed from the holotype just below. Redescription. Length ca 29 mm, width of midbody pro-and metazona 2.2 and 3.3 mm, respectively. Coloration of alcohol material upon long-term preservation rather uniformly brown (Fig. 39) (vs very dark brown, as given in the original description (Attems 1930a)).

Orthomorpha unicolor
All other characters as in O. hydrobiologica, except as follows.
Remarks. This variety was elevated to a full species by Jeekel (1963Jeekel ( , 1964Jeekel ( , 1968, also treated as such by Hoffman (1973) and Golovatch (1998). Lectotype. ♂ of Pratinus granosus (NHMW-3516), Vietnam, Lamdong Prov., Peak Lang Biang, 1938-1939, leg. C. Dawydoff. Lectotype designation proposed herewith is necessary to ensure the species is based on a complete male coming from a certain locality, because (1) Attems (1953) had provided no information on the number of syntypes, and (2) he stated their provenance to have been both from Xieng Kunang, Luang Prabang Province, Laos and Peak Lang Biang, Lamdong Province, Vietnam. Redescription. Length 41 mm, width of midbody pro-and metazona 3.1 and 4.4 mm, respectively (vs 38 mm in length and 4.6 mm in width, as given in the original description (Attems 1953)). Coloration of alcohol material upon long-term preservation rather uniformly light brown (Fig. 41) (vs black-brown with rather contrasting light brown to yellow-brown prozona, paraterga and venter, as well as red-brown legs, as given in the original description (Attems 1953)).
Orthomorpha rotundicollis (Attems, 1937) http://species-id.net/wiki/Orthomorpha_rotundicollis  Lectotype designation proposed herewith is necessary to ensure the species is based on a complete male coming from a certain locality, because (1) Attems (1937Attems ( , 1938 Attems, 1937. A, B, J anterior part of body, dorsal, lateral and dorsal views, respectively C, D, K segments 10 and 11, dorsal, lateral and dorsal views, respectively e-G, l posterior part of body, lateral, dorsal, ventral and dorsal views, respectively h, i sternal cones between coxae 4, subcaudal and sublateral views, respectively. had provided no information on the number of syntypes, and (2) he stated their provenance to have been both from Arbre-Broyé and Dalat, Vietnam.
Remark. This species is known from Lamdong Province, southern Vietnam and Luang Prabang Province, Laos (Attems 1938(Attems , 1953. The type locality of both O. rotundicollis and O. tuberculata being exactly the same (Arbre-Broyé at Peak Lang Biang), and the differences between them so minor, rather to be treated as infraspecific variations, we are inclined to formally synonymize these species. Indeed, distinctions are observed only in O. rotundicollis showing a slightly more rounded caudal corner of the paraterga on the collum (vs slightly more angular in O. tuberculata), in the front row of metatergal setae (= insertion points) borne on virtually fully obliterated knobs (vs on minute knobs in O. tuberculata), and in the apical papillae on the epiproct directed more caudally than ventrally (vs more ventrally than caudally in O. tuberculata) (Attems 1937(Attems , 1938(Attems , 1953. We can also add another two differences: paraterga 18 and 19 seem to be a little shorter in O. rotundicollis than in O. tuberculata, and the caudal row of tubercles on a few caudalmost metaterga demonstrating a pattern of 3+4 or 4+3 in O. tuberculata (vs invariably 3+3 in O. rotundicollis).
The above is a combined redescription, based on material of both nominate species.
Sterna sparsely setose, without modifications, but with two large, rounded, fully separated, setose cones between ♂ coxae 4 ( Fig. 47H & I). A paramedian pair of small tubercles in front of gonopod aperture. Legs long and slender, midbody ones ca 1.2-1.3 (♂) or 0.8-0.9 (♀) as long as body height, prefemora without modifications, tarsal brushes present until ♂ legs 5. Gonopods (Fig. 48) simple. Coxa long and slender, with several setae distodorsally. Prefemur densely setose, nearly 3 times shorter than femorite + "postfemoral" part. Femorite very slender, slightly curved, very slightly enlarged distad, "postfemoral" part demarcated by an oblique lateral sulcus; tip of solenophore small, trifid, with two denticles (terminal tooth larger, middle one smaller) and a small subterminal lobule. Lectotype designation proposed herewith is necessary to ensure the species is based on a complete male, because the type series was stated to have been shared between the collections of the Berlin and Vienna museums (Attems 1898).
Remarks. The above redescription is meant to augment the fairly complete one by Jeekel (1980b) which was also based on syntypes. Redescription. Length 39 mm, width of midbody pro-and metazona 2.9 and 4.4 mm, respectively. Coloration of alcohol material upon long-term preservation dark castaneous brown with contrasting yellowish paraterga; venter, legs yellownish and tip of epiproct light red-brown, antennae also light red-brown, but antenomere 6 slightly infuscate, brownish, antenomere 7 dark brown, and tip of antennae pallid (Fig. 55).
Sterna sparsely setose, without modifications; cross-impressions shallow; a pair of strongly separated, anteroventrally directed, narrowly rounded, setose cones between ♂ coxae 4 ( Fig. 55H & I). A paramedian pair of small tubercles in front of gonopod aperture. Legs long and slender, midbody ones ca 1.3-1.5 times as long as body height, prefemora without modifications, ♂ tarsal brushes present until on legs of segment 17. Gonopods (Fig. 56) a little more complex. Coxa long and slender, with several strong setae distodorsally. Prefemur densely setose, about half the length of femorite + "postfemoral" part. Femorite slender, slightly curved and nearly not enlarged distad, with a small, but conspicuous ventral knob near base of lamina lateralis, with a "postfemoral" part demarcated by a distinct, oblique, lateral sulcus; solenophore with a tridentate tip, middle denticle shorter than terminal tooth, but longer than a small subterminal lobule; solenomere long, flagelliform, a short tip exposed.

Orthomorpha murphyi
Coloration of live animals (Fig. 58A) uniformly blackish brown with only slightly lighter paraterga, venter and legs; coloration of alcohol material upon long-term preservation faded to a light brown (holotype) with contrasting pallid paraterga, venter, legs and antennae (Fig. 57); coloration of rather freshly alcohol-preserved material blackish brown with likewise strongly faded paraterga, venter and legs (Fig. 58B-H).    Remarks. The original description of this species was so complete and detailed (Hoffman 1973) that no redescription seems to be necessary. Instead, we only provide new illustrations  showing the coloration, structural details, and gonopod conformation of O. murphyi, based both on the holotype and new samples. Holotype. ♂ (NHMW-3509), Indonesia, Sumatra, Lampung Prov., Way Kambas, forest road, ca 10 m, 26.12.1993, leg. R. Melisch.
Remarks. The original description of this species was so complete and detailed (Golovatch 1997b) that no redescription seems to be necessary. Instead, we only provide new illustrations (Figs 62 & 63) showing the coloration, structural details and gonopod conformation of O. melischi, based on the holotype.   mm in width on midbody pro-and metazona, respectively, both in ♂ and ♀, as given in the original description (Golovatch 1998)).
Coloration of live animals (Fig. 65A) dark brown with contrasting orange paraterga and orange-brown hind parts of metaterga; coloration of alcohol material upon long-term preservation faded to basically light brown (holotype) to dark castaneous brown with contrasting pallid to light greyish paraterga, most of mid-dorsal parts of metaterga and prozona, as well as epiproct (Figs 64 & 65B-H).
Remarks. The original description of this species was so complete and detailed (Golovatch 1998) that no redescription seems to be necessary. Instead, we only provide   alcohol material upon long-term preservation faded to brown (holotype) with contrasting pallid to light yellow paraterga, middle parts of metaterga and prozona, and venter .
Remarks. The original description of this species was so complete and detailed (Golovatch 1998) that no redescription seems to be necessary. Instead, we only provide new illustrations  showing the coloration, structural details and gonopod conformation of O. horologiformis, based both on the holotype and new samples.
Coloration of live animals (Fig. 75A) blackish-brown with contrasting yellow paraterga and epiproct, most of metaterga being light grey-brown; coloration of alcohol material upon long-term preservation blackish-brown to faded dark castaneous brown with contrasting yellow to pallid paraterga, epiproct and hind halves of metaterga (Figs 74,; pattern mostly light creamy-yellowish, including paraterga's dorsal and ventral parts, with contrasting dark brown to blackish cingulations of prozona and of anterior parts of metaterga. Collum either completely light or also bearing a dark, oblong, transverse, more or less large spot in front 1/3. Calluses of several midbody and/or posterior metaterga (16)(17)(18)(19) can be less strongly convex laterally (Fig. 75L & M).   Tip of solenophore narrowly rounded to sharply dentiform, rather depending on aspect .
Remarks. The original description of this species was complete and detailed enough (Golovatch 1998) to require no complete redescription. Instead, we provide new illustrations      Descriptive notes. Coloration of alcohol material upon long-term preservation probably faded to dark castanceous brown with contrasting pallid paraterga, middle part of prozona, epiproct, venter and pleurosternal carinae (Fig. 79).

Orthomorpha thalebanica
Coloration of live animals (Fig. 82A) nearly same as in specimens kept in alcohol for a long time, except for paraterga being slightly more infuscate in live individuals, in all  cases dark castaneous brown with contrasting light yellow-brown to pallid paraterga, tip of epiproct, venter and pleurosternal carinae; rear 1/2-1/4 of metaterga and mid-dorsal regions of prozona slightly infuscate, yellow-brown to nearly pallid (Figs 81 & 82).
Remarks. The original description of this species was so complete and detailed (Golovatch 1998) that no redescription seems to be necessary. Instead, we only provide new illustrations  showing the coloration, structural details and gonopod conformation of O. thalebanica, based both on the holotype and new samples. This species appears to be rather widespread in southern Thailand (Map 3).
Collum with caudal corner of paraterga ranging from obtusangular (described as being about 100˚ in holotype, Fig. 86A & B), via subrectangular (Fig. 87C), to evidently acutangular. Calluses of paraterga mostly broad and extending behind tergal margin, increasingly well so on segements 7(8)-19, but sometimes slightly narrower and not surpassing it, forming instead a subrectangular turn mesally . Caudal corner of paraterga remaining from acute and pointed thoughout (♂ from Tham Khao Phanomwang Temple, Fig. 87N) to mostly narrowly rounded (♂ from Tham Sri Kesorn, Fig. 87I), with all intergradations in-between (Figs 86A,C & F,87A,B,D,. Metatergal sulcus visible on segments 5-18, more rarely incomplete also on segment 19 (holotype). Pleurosternal carinae expressed as complete high crests with a sharp caudal tooth on segment 2, thereafter increasingly well divided into a front bulge and a caudal tooth, the latter sharp or rounded, on segments 2-7; both front bulge and caudal tooth increasingly strongly reduced either until segment 10 (11), with a small sharp tooth until segment 16 (17) (♂), or expressed as complete high crests with a sharp caudal tooth on segments 2-4, thereafter increasingly well divided into a front bulge and a caudal tooth, sharp or rounded, on segments 5-10, a small sharp tooth until segment 16 (17) (♀). Midbody legs ca 1.1-1.3 (♂) or 0.9-1.2 times (♀) as long as body height.
Base of lamina lateralis with a small, but conspicuous ventral knob (like in O. fluminoris). Tip of gonopod with terminal lobule longest, bearing microdenticulations or a more or less evident fringe at external edge (Fig. 89C & D). Middle spiniform prong sometimes slightly smaller than usual (Fig. 90).
Remark. This species appears to be widespread in southern Thailand (Map 4).    Coloration of live animals (Figs 91A & 92A) blackish brown with rather poorly contrasting light orange-brown to light brown paraterga and epiproct, rear halves to nearly entire metaterga sometimes a little more infuscate, brownish; coloration upon long-term preservation in alcohol basically same, but paraterga, epiproct, most of metatergal surface, as well as frontodorsal parts of prozona contrasting pallid, yellowish or light grey-brown . A light centrocaudal spot to a broad caudal band on the collum seems to be characteristic of this species, despite its size variation from small and vague to large and clear in alcohol-preserved material (Figs 91B & C,92B & C).
Remarks. Jeekel (1970), when redescribing O. insularis Pocock, 1895, from material from Myanmar, also emphasized clear variation in the width of the calluses and of the outlines of some paraterga. This has allowed him to synonymize several other nominate congeners, revised from type material from Myanmar, with O. insularis (see catalogue section above). The above abundant material from Thailand confirms a profound variation range in size, coloration, shapes of the collum and following paraterga etc. This variation is deemed to be only individual, as our examination of larger series shows. No complete redescription is provided here, because that of Jeekel (1970) is detailed enough.
This species appears to be widespread over much of Thailand, as well as in the adjacent parts of Myanmar (Map 4). Enghoff (2005), Decker (2010) and Likhitrakarn et al. (2010a), in their faunistic accounts on Thai millipedes, mistakenly referred to O. intercedens, which is long known to be only a junior synonym of O. insularis (see Jeekel 1970). Remarks. This species still remains dubious (Golovatch 1998), because it is based on a ♀ holotype (Pocock 1889). Although it could be incorporated in our key below, a redescription of ♂ topotypic material is necessary to confirm the species status of O. crucifer. At present it is only known from King Island, Mergui Archipelago, Myanmar (Pocock 1889). Remarks. This species has been beautifully redescribed by Jeekel (1970) from non-type ♀ material from southern Tenasserim (= Tanintharyi), Myanmar, referred to by Pocock (1895). Based on the illustration of a gonopod by Attems (1937), O. karschi appears to be very similar to O. insularis, apparently differing only in a slightly shorter gonofemorite (Jeekel 1970). However, Pocock's (1889) original drawing shows the femorite to be as slender as in O. insularis. There is only a single micropreparation in the NHMW collection containing the gonopod depicted by Attems (1937). This species seems to be endemic to southern Myanmar together with the adjacent Mergui Archipelago and Thailand. Attems (1937) referred to material from Siam (= Thailand), without giving a precise locality, but Enghoff (2005), in his catalogue of the Thai millipedes, must have overlooked that record. Remarks. This species has been adequately redescribed and illustrated from a ♂ syntype by Golovatch (1997b), thus requiring no further revision. O. conspicua is only known from Bogor, Java, Indonesia (Pocock 1894). Remarks. This species has been adequately redescribed and illustrated from a ♂ syntype by Golovatch (1997b), thus requiring no further revision. O. weberi is only known from Bogor, Java, Indonesia (Pocock 1894).
Coloration of alcohol material after long-term preservation castaneous brown with a pattern of contrasting whitish to yellow paraterga and epiproct, and mostly greyishwhite posterior halves of postcollum metaterga; head and antennomeres 6 and 7 brown to dark brown; venter and a few basal podomeres light brown to yellow-brown, legs growing infuscate (brown) distally; tip of antenna pallid (Fig. 97A-G).
Remark. This new species is rather widespread in eastern Thailand (Map 2). Name. To emphasize the mostly strongly elevated paraterga. Diagnosis. Differs by mostly strongly elevated paraterga, coupled with two small sternal cones between ♂ coxae 4 (see also Key below).
Coloration of live material (Fig. 100A) blackish to blackish-brown with contrasting pinkish paraterga legs, and tip of epiproct; coloration of alcohol material after long-term preservation blackish-brown with contrasting light yellowish calluses; two paramedian spots divided by a broad, blackish, axial stripe on prozona; lateral parts of Figure 100. Orthomorpha elevata sp. n., ♂ holotype. A habitus, live coloration B, C anterior part of body, dorsal and lateral views, respectively D, e segments 10 and 11, dorsal and lateral views, respectively F, G, h posterior part of body, dorsal, ventral and lateral views, respectively i, J sternal cones between coxae 4, subcaudal and sublateral views, respectively. paraterga near calluses, tip of epiproct, legs and venter light yellow-brown, legs slightly infuscate distally; antennae brown, distal part of antennomere 5, distal 2/3 of antennomere 6 and entire antennomere 7 blackish-brown (Fig. 100B-H).
Remark. This new species is rather widespread in northern Malaysia (Map 2).  Name. To emphasize the strong similarity to O. elevata sp. n. Diagnosis. Comes closest to O. elevata sp. n., but differs in the paraterga lying below the dorsum, coupled with pleurosternal carinae present at least as a caudal denticle until segment 16 (♂) or 13 (♀) (see also Key below).
Coloration of alcohol material after long-term preservation brown to dark brown with contrasting whitish calluses, lateral parts of paraterga close to calluses and, some- times, entire epiproct, as well as light yellow to yellow-brown legs and epiproct; two paramedian spots divided by a narrow, brown or grey-brown axial stripe on prozona and central parts of metaterga slightly lighter than background, light brown, except for an infuscate cross composed of transverse sulcus and axial line, the latter often extending from collum to tip of epiproct .
All other characters as in O. elevata sp. n., except as follows.
Remark. This new species is rather widespread in northern Malaysia (Map 2).  Name. To emphasize the type locality. Diagnosis. Differs by a strongly contrasting colour pattern, coupled with pleurosternal carinae represented by complete crests bulged anteriorly and with a sharp caudal tooth on segments 2-7, thereafter only a sharp caudal tooth on segments 8-16 (♂), or crests bulged anteriorly and with a sharp caudal tooth on segments 2-4, thereafter only a small sharp caudal tooth on segments 5-14 (♀) (see also Key below).
Coloration of live animals blackish, paraterga and epiproct contrastingly creamy yellow, legs and venter dark brown to blackish; coloration of alcohol material after long-term preservation dark brown to blackish, paraterga (marbled at base) and epiproct faded to pale yellow, legs and venter more pale brown (Fig. 106A-G).
Remark. This new species is only known from one of the islets of Similan Archipelago, Thailand (Map 2).  Coloration of live animals blackish-brown, calluses of paraterga (especially caudal parts) and distal half of epiproct contrasting red-brown; legs and venter yellow to light brown (Fig. 109A); coloration of alcohol material after long-term preservation faded to dark castaneous brown, paraterga contrasting pallid to very light brownish, antennomeres 1-4 very light brown, distal antennomeres brown (Fig. 109B-H).
Remarks. The original description of O. consocius Chamberlin, 1945 being anecdotal (Chamberlin 1945), above is its redescription, based on the holotype coming from Tjibodas, Java, Indonesia. A comparison of the redescription with the original description of O. butteli Carl, 1922, also from Tjibodas, leaves no doubt about their synonymy, because they coincide in virtually every detail, including gonopod structure. Hence the new synonymy advanced.
Sterna sparsely setose, without modifications; cross-impressions rather deep. Legs moderately long and slender, midbody ones ca 1.1-1.2 times as long as body height.
Remarks. This species has been described from a series of ♀ syntypes, still known only from the type locality: Tengger Mountains, eastern Java, Indonesia (Attems 1898 only O. tenuipes has also been described from Tengger Mountains, but it is evidently different from O. herpusa in showing higher and laterally better incised paraterga with much broader calluses etc. (Fig. 49). Among the best candidates to match the description of O. herpusa are perhaps O. beaumontii (Figs 1 & 2), O. hydrobiologica (Fig. 37), O. unicolor (Fig. 39), and O. zehntneri (Fig. 53), but still there are certain differences in ♀ somatic characters alone, often profound enough. So only a strict ♂ topotype is necessary to obtain and examine to ultimately establish the identity of O. herpusa. Furthermore, this species might as well prove to belong to another genus of Orthomorphini, for instance Nesorthomorpha Jeekel, 1980, with eight species, all endemic to Java and often showing similarly strongly developed paraterga (Golovatch and Wytwer 2001).  Syntypes. 2 ♀ (NHMW-7986), Seychelles, Mahé Island, primeval forest, 1895, leg. A. Brauer. Descriptive notes. Length 19-20 mm, width of midbody pro-and metazona 2.1-2.2 and 2.5-2.6 mm, respectively. Coloration of alcohol material upon long-term preservation uniformly light grey-brown (Fig. 115).
Metaterga densely and irregularly setose. All other somatic characters as in Fig. 115.
Remarks. This species has been described from three ♀ syntypes, still known only from the type locality: Mahé Island, Seychelles (Golovatch & Gerlach 2010). Superficially, it differs readily from the only other paradoxosomatid endemic to the Seychelles, Diglossosternoides curiosus Golovatch and Korsós, 1992, tribe Eustrongylosomatini, in the remarkably densely setose collum and following metaterga (Golovatch and Korsós 1992).
Based both on the morphological characters (e.g. the narrow paraterga and densely setose metaterga) and distribution, there can be no doubt that O. crinita has nothing to do with Orthomorpha. Remarks. The paraterga in "O." variegata seem to be too narrow to represent a species of Orthomorpha, as beautifully redescribed by Brölemann (1904) from the ♀ holotype. Golovatch (1998) included it into his key to Orthomorpha species for the sake of completeness. At present we are inclined to follow Jeekel (1968) and exclude this species from Orthomorpha altogether.

"Orthomorpha" bisulcata Pocock, 1895
Orthomorpha bisulcata Pocock 1895: 808 (D). Remarks. The paraterga in O. bisulcata are definitely too narrow to represent a species of Orthomorpha (Pocock 1895;Jeekel 1965). Attems (1903) recorded it from Tjibodas, Java, Indonesia, apparently a misidentification. Both Attems (1937) and Jeekel (1968) referred to it as a species incertae sedis, because it was based only on ♀ material. It has been adequately redescribed by Jeekel (1965) from the ♀ lectotype coming from Rangoon, Myanmar. Golovatch (1998) included it into his key to Orthomorpha species for the sake of completeness. At present we are inclined to follow Jeekel (1968) and exclude this species from Orthomorpha altogether. Remarks. The paraterga in O. coxisternis are definitely too narrow to represent a species of Orthomorpha (Pocock 1895;Jeekel 1965). Both Attems (1937) and Jeekel (1968) referred to it as a species incertae sedis, because it was based only on ♀ material. It has been adequately redescribed by Jeekel (1965) from the ♀ holotype coming from Bhamo, Myanmar. Even though Golovatch (1998) included it into his key to Orthomorpha species for the sake of completeness, at present we are inclined to follow Jeekel (1968) and exclude this species from Orthomorpha altogether. Remarks. According to the original description (Pocock 1895), the gonopod of this species looks absolutely different from the Orthomorpha type, the solenomere showing a couple of denticles near the base, while the solenophore (= lamina lateralis) is produced dorsally before subtending the solenomere. Such a conformation resembles that of a species of the mainly Papuan tribe Eustrongylosomatini, but the only member of this tribe known to occur west of Borneo is Diglossosternoides curiosus, from the Seychelles (see above). Both Attems (1937) and Jeekel (1968) referred to O. oatesii as a species incertae sedis, but Golovatch (1998)  Gonopod with a long subcylindrical coxite and a usual, cylindrical cannula. Telopodite long and slender, modestly curved. Prefemoral part densely setose, more than 2 times shorter than femorite. The latter without evidence of torsion, slightly enlarged distally, without sulcus demarcating a "postfemoral" part. Solenophore consisting of subequally modestly developed laminae lateralis, and medialis, both sheathing a similarly long, simple, flagelliform solenomere with a barely exposed tip; tip of solenophore never deeply split, poorly bi-or trifid, at least some of its apical prongs being short spines.
Coloration of alcohol material after long-term preservation faded to uniformly light brown (Fig. 116) (vs castaneous brown to light brown, as given in the available descriptions (Attems 1937(Attems , 1938).

Conclusion
The genus Orthomorpha as currently defined is the largest in the family Paradoxosomatidae in Southeast Asia, at present comprising 51 identifiable species. Some of them are still rather poorly distinguished from their superficially most similar congeners. In particular, such species pairs as O. lauta vs O. insularis or O. horologiformis vs O. pterygota appear to be quite variable morphologically, while their distributions show no considerable gaps (Map 4). So molecular analyses, for instance bar-coding, would be most desirable in order to shed additional light on the identities and affinities of such variable species. There can be no doubt that further collecting efforts, especially in still very poorly explored regions as Laos, Myanmar and Cambodia, also some parts of Vietnam, will reveal many more species of Orthomorpha. Only Thailand and northern Malaysia can be said to be fairly well covered in this respect, particularly so after the present revision. At present we can no longer suggest any infrageneric classification better than one based on the structure of the gonopod tip, and we abandon a division into species groups altogether.