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.

The dragon millipede genus Desmoxytes s.l. is split into five genera, based on morphological characters and preliminary molecular phylogenetic analyses. The present article includes a review of Desmoxytes s.s., while future articles will deal with Hylomus Cook and Loomis, 1924 and three new genera which preliminarily are referred to as the ‘acantherpestes’, ‘gigas’, and ‘spiny’ groups. Diagnostic morphological characters of each group are discussed. Hylomus is resurrected as a valid genus and the following 33 species are assigned to it: H. asper (Attems, 1937), comb. n., H. cattienensis (Nguyen, Golovatch & Anichkin, 2005), comb. n., H. cervarius (Attems, 1953), comb. n., H. cornutus (Zhang & Li, 1982), comb. n., H. draco Cook & Loomis, 1924, stat. rev., H. enghoffi (Nguyen, Golovatch & Anichkin, 2005), comb. n., H. eupterygotus (Golovatch, Li, Liu & Geoffroy, 2012), comb. n., H. getuhensis (Liu, Golovatch & Tian, 2014), comb. n., H. grandis (Golovatch, VandenSpiegel & Semenyuk, 2016), comb. n., H. hostilis (Golovatch & Enghoff, 1994), comb. n., H. jeekeli (Golovatch & Enghoff, 1994), comb. n., H. lingulatus (Liu, Golovatch & Tian, 2014), comb. n., H. laticollis (Liu, Golovatch & Tian, 2016), comb. n., H. longispinus (Loksa, 1960), comb. n., H. lui (Golovatch, Li, Liu & Geoffroy, 2012), comb. n., H. minutuberculus (Zhang, 1986), comb. n., H. nodulosus (Liu, Golovatch & Tian, 2014), comb. n., H. parvulus (Liu, Golovatch & Tian, 2014), comb. n., H. phasmoides (Liu, Golovatch & Tian, 2016), comb. n., H. pilosus (Attems, 1937), comb. n., H. proximus (Nguyen, Golovatch & Anichkin, 2005), comb. n., H. rhinoceros (Likhitrakarn, Golovatch & Panha, 2015), comb. n., H. rhinoparvus (Likhitrakarn, Golovatch & Panha, 2015), comb. n., H. scolopendroides (Golovatch, Geoffroy & Mauriès, 2010), comb. n., H. scutigeroides (Golovatch, Geoffroy & Mauriès, 2010), comb. n., H. similis (Liu, Golovatch & Tian, 2016), comb. n., H. simplex (Golovatch, VandenSpiegel & Semenyuk, 2016), comb. n., H. simplipodus (Liu, Golovatch & Tian, 2016), comb. n., H. specialis (Nguyen, Golovatch & Anichkin, 2005), comb. n., H. spectabilis (Attems, 1937), comb. n., H. spinitergus (Liu, Golovatch & Tian, 2016), comb. n., H. spinissimus (Golovatch, Li, Liu & Geoffroy, 2012), comb. n. and H. variabilis (Liu, Golovatch & Tian, 2016), comb. n. Desmoxytes s.s. includes the following species: D. breviverpa Srisonchai, Enghoff & Panha, 2016; D. cervina (Pocock,1895); D. delfae (Jeekel, 1964); D. des Srisonchai, Enghoff & Panha, 2016; D. pinnasquali Srisonchai, Enghoff & Panha, 2016; D. planata (Pocock, 1895); D. purpurosea Enghoff, Sutcharit & Panha, 2007; D. takensis Srisonchai, Enghoff & Panha, 2016; D. taurina (Pocock, 1895); D. terae (Jeekel, 1964), all of which are re-described based mainly on type material. Two new synonyms are proposed: Desmoxytes pterygota Golovatch & Enghoff, 1994, syn. n. (= Desmoxytes cervina (Pocock, 1895)), Desmoxytes rubra Golovatch & Enghoff, 1994, syn. n. (= Desmoxytes delfae (Jeekel, 1964)). Six new species are described from Tha...

The genus Tylopus currently contains 41 species, all keyed and mapped, including five new from northern Thailand: Tylopus bispinosus sp. n., Tylopus grandis sp. n., Tylopus extremus sp. n., Tylopus veliger sp. n. and Tylopus parajeekeli sp. n. Species of Tylopus are predominantly forest-dwellers, especially in montane habitats where up to 9–10 species can coexist per faunule. We expect many more congeners to be discovered in future, in particular from poorly or relatively poorly prospected regions such as Laos (only two species recorded), Cambodia (no species yet), Vietnam (a few species), Myanmar (a few species) and southern China (one species only). Because the genus is so species-rich and as yet so poorly sampled, a phylogenetic analysis of Tylopus would be premature.

Two new species of Glyphiulus are described and illustrated from northern Laos. The epigean Glyphiulus subbedosae Likhitrakarn, Golovatch & Panha, sp. n. is the second member of the granulatus-group to be found in that country and it seems to be especially similar to G. bedosae Golovatch, Geoffroy, Mauriès & VandenSpiegel, 2007. However, it differs from the latter species by a row of several strong setae near the median marginal ridge on the paraprocts, combined with the gnathochilarium being considerably less densely setose on the caudal face, and the anterior gonopods showing a pair of smaller, apical, but larger lateral teeth on the coxosternal plate. Glyphiulus semicostulifer Likhitrakarn, Golovatch & Panha, sp. n. is the fourth member of the javanicus-group to be discovered in Laos, taken from a cave. It seems to be particularly similar to G. costulifer Golovatch, Geoffroy, Mauriès & VandenSpiegel, 2007, but is distinguished by the more sparsely alveolate background fine structure of the metazonae, coupled with the gnathochilarium being considerably less densely setose on the caudal face, much stronger paramedian prongs and 4-segmented telopodites on ♂ coxae 1, the slightly longer and more slender apicoparamedian sternal projections on the anterior gonopods, and the much longer flagella of the posterior gonopods. An identification key to and a distribution map of Glyphiulus species in Laos are also presented.

Four new dragon millipede species of the genus Desmoxytes from northern Thailand are described and illustrated: D. des sp. n. from Chiang Mai Province, D. breviverpa sp. n. from Phrae Province, D. takensis sp. n. from Tak Province and      D. pinnasquali sp. n. from Phitsanulok Province. The new species were compared with type specimens of closely related species and were all found to exhibit explicit morphological differences from these. They can be distinguished from other members of Desmoxytes by the shape of the gonopods, the sternal process between male coxae 4, the pattern of spines or tubercles on the metaterga, and the shape of the paraterga. The coloration of all new species is clearly aposematic: ranging from purple-pink to red. The new species are discussed in relation to their congeners, and a distribution map is provided.

The ‘acantherpestes’ group of dragon millipedes, formerly placed in the genus Desmoxytes Chamberlin, 1923, is revised and assigned to the new genus Nagaxytes Srisonchai, Enghoff & Panha gen. nov. Desmoxytes acantherpestes Golovatch & Enghoff, 1994 is the type species of the new genus and is redescribed as N. acantherpestes (Golovatch & Enghoff, 1994) gen. et comb. nov. Three new species are described from Thailand: N. erecta Srisonchai, Enghoff & Panha gen. et sp. nov. and N. gracilis Srisonchai, Enghoff & Panha gen. et sp. nov. from Kanchanaburi Province, and N. spatula Srisonchai, Enghoff & Panha gen. et sp. nov. from Tak Province. All new species are endemic to western Thailand and all are restricted to limestone habitats. Complete illustrations of external morphological characters, an identification key, and a distribution map are provided.

At the present, the millipede fauna of Laos comprises only 34 species from 20 genera, 13 families and 7 orders. These counts certainly represent but a minor fraction of the country's real diversity of Diplopoda even at the ordinal level, let alone at lower ones. Based on the available information from the adjacent parts of China, Thailand, Myanmar, Vietnam and/or Cambodia, the orders Polyxenida, Sphaerotheriida, Chordeumatida, Julida and Polyzoniida must occur in Laos, may be also Glomeridesmida, Siphonocryptida and Stemmiulida, but none has been recorded there yet. Moreover, even some ubiquitous "tramp" species, such as Glyphiulus granulatus (Gervais, 1847), Trigoniulus corallinus (Gervais, 1847), Desmoxytes planata (Pocock, 1895) or Oxidus gracilis (C. L. Koch, 1847), have hitherto not been found in Laos. This shows that a lot more collecting efforts, which have heretofore been rather strongly biased to caves, are required to amass a representative material of Diplopoda of Laos and make it available for study.

The sericata-group of Orthomorpha is revised and shown to comprise six species, five of which have been collected only in Thailand, including O. enghoffi sp. n., O. alutaria sp. n., O. parasericata sp. n. and O. asticta sp. n. Both O. sericata Jeekel, 1964 and O. subsericata Golovatch, 1997 are redescribed and illustrated, in part based on type material. A key is provided to all of the species in the group, and their distributions are mapped.