Eutrichodesmus Silvestri, 1910

Srisonchai, Ruttapon, Likhitrakarn, Natdanai, Sutcharit, Chirasak, Jeratthitikul, Ekgachai, Siriwut, Warut, Thrach, Phanara, Chhuoy, Samol, Ngor, Peng Bun & Panha, Somsak, 2020, A new micropolydesmoid millipede of the genus Eutrichodesmus Silvestri, 1910 from Cambodia, with a key to species in mainland Southeast Asia (Diplopoda, Polydesmida, Haplodesmidae), ZooKeys 996, pp. 59-91 : 59

Genus Eutrichodesmus Silvestri, 1910

Type species.

Eutrichodesmus demangei Silvestri, 1910

All species included.

The genus Eutrichodesmus currently contains 55 species, including the new one described herein, see Table 1 .

Recorded distributions of all known species.

Based on all the recent literature and excluding the newly-described species, the genus Eutrichodesmus is widely distributed in southern Japan, Taiwan, southern China, mainland Southeast Asia (Malaysia, Laos, Thailand and Vietnam), Indonesia (Sulawesi) and Melanesia (Vanuatu) ( Golovatch et al. 2009a, 2009b, 2015, 2016; Liu et al. 2017; Golovatch and Liu 2020; see Table 1 ). No Eutrichodesmus species have hitherto been reported from Cambodia.

Updated diagnosis of the genus Eutrichodesmus Silvestri, 1910.

Golovatch et al. (2009a, 2009b) provided a complete diagnosis of the genus, as well as the main structural details of all genera in the family Haplodesmidae . It is therefore relatively easy to provide a morphological overview of Eutrichodesmus . However, as the genus shares some characters with certain confamilial genera, i.e. Cylindrodesmus Pocock, 1889; Doratodesmus Cook in Cook and Collin, 1985; and Helodesmus Cook, 1896, a refined diagnosis seems to be warranted. The more so as, since 2009, 18 further species of Eutrichodesmus have been described, adding a number of morphological traits across the genus ( Makhan 2010; Golovatch et al. 2010, 2015, 2016; Liu et al. 2017; Liu and Wynne 2019). The amended diagnosis of Eutrichodesmus is chiefly based on that by Golovatch et al. (2009a, 2009b).

The genus Eutrichodesmus differs from all other Haplodesmidae by showing the following combination of characters. Body small (ca. 3.5-14 mm in length), with 19-20 rings; usually “doratodesmid” (= capable of volvation); conglobation usually complete, but sometimes incomplete. Tegument: collum and metaterga usually microgranulate and microvillose; prozonae often alveolate. Metatergawith or without mid-dorsal projections (outgrowths); usually with two or three rows of conspicuous tubercles (seldom four or more), often arranged mixostictic (irregular in axial direction) or, sometimes, isostictic (regular in axial direction). Paraterga short or long, usually lobulate. Ozopores usually present on rings 5, 7, 9, 10, 12, 13, 15-19, rarely reduced or absent; with or without porosteles. Gonopod: Coxae often microgranulate; usually abundantly setose, sometimes with a distolateral outgrowth. Telopodite usually long and slender; basal half of telopodite (= prefemoral part) densely setose; often with a distofemoral process, conspicuous, located laterally on femorite, sometimes absent. Acropodite well-developed, conspicuous. Solenomere often completely fused to acropodite (solenomere = acropodite), rarely separated and forming a lobe. Seminal groove running on mesal side of prefemur, usually terminating at about halfway of acropodite to distal region; with or without hairpad.