Two new species of Plusioglyphiulus are described from southern Cambodia. Plusioglyphiulus biserratus sp. nov. is clearly distinguished from all congeners by the shape of the telopodites of the posterior gonopods which are distinctly serrate laterally and by the anterior gonopods showing only a pair of single, smooth and curved coxosternal processes. Plusioglyphiulus khmer sp. nov. is distinguished by having most crests on the collum being complete and male legs 1 showing long, prominent, one-segmented telopodites, coupled with the oblong-subtrapeziform, membranous, posterior gonopods with a small bifid process at about a third of the telopodite length. Notes on the variation of Plusioglyphiulus boutini Mauriès, 1970 are also given, including a colour photograph of fresh, live material. A key to all four species of Plusioglyphiulus currently known to occur in Cambodia is also presented.
Keywords: cave, diplopod, forest, Indochina, key
Family Cambalopsidae Cook, 1895
Genus Plusioglyphiulus Silvestri, 1923
Plusioglyphiulus dubius (Attems, 1938)
Plusioglyphiulus boutini Mauriès, 1970
Plusioglyphiulus biserratus sp. nov.
Name: To emphasize the telopodites of the posterior gonopods being clearly serrate apicolaterally; adjective.
Diagnosis: This new species is distinguished from all congeners by its anterior gonopod structure: in having only a pair of single coxosternal processes (cxp) (Fig. 3H, I) it is especially similar to that observed in P. hoffmani Golovatch, Geoffroy, Mauriès & VandenSpiegel, 2009, but both these species differ in cxp being smooth and distally curved in P. biserratus sp. nov. vs serrate and suberect in P. hoffmani. The posterior gonopods of P. biserratus sp. nov. are unique in showing laterally fringed/serrate telopodites (te), both elongate and membranous (Fig. 3J, K), and ♂ legs 1 with very long, slender and one-segmented telopodites (Fig. 3D, E).
Plusioglyphiulus khmer sp. nov.
Name: To emphasize “khmer”, referring to the main people of Cambodia; a noun in apposition.
Diagnosis: This new species differs from all congeners by all crests on the collum being undivided, mostly complete (Fig. 5B) and male legs 1 with very long and one-segmented telopodites (Fig. 5D, E), as well as by the presence of 2+2 paramedian, characteristically long, slender, coxosternal processes of the anterior gonopods, a shorter and only apically curved posterior (cxp1) pair, and a longer, mesally micropapillate and regularly curved anterior (cxp2) one (Fig. 5H, I); the posterior gonopods are oblong-subtrapeziform, membranous, each with a small apical spike (d) and a bifid process (k) at about 1/3 telopodite length on anterior face (Fig. 5J, K).
According to the latest catalogue of the Diplopoda of Cambodia (Likhitrakarn et al. 2015), and considering two new Plusioglyphiulus described above, the millipede fauna of the country currently comprises only 21 species from 15 genera, 12 families, and eight orders. In addition, all new records came from only the southern parts of Cambodia. The collecting localities for the millipedes in Cambodia are still very few, especially when compared to the neighboring countries such as Thailand (more than 300 reported localities) (i.e. Likhitrakarn et al. 2011; Pimvichai et al. 2016; Srisonchai et al. 2018).
Finally, as regards the present knowledge of the Cambalopsidae, we seem to have only touched the tip of the diversity iceberg of the family (Golovatch et al. 2007b). Cambalopsids are especially diverse and common in karst areas, where they are usually associated with bat guano in caves (Golovatch 2015). There is little doubt that many additional new species of Diplopoda, including Cambalopsidae, can be expected to be revealed by future explorations in Cambodia, especially in the limestone karsts of the country.
Natdanai Likhitrakarn, Sergei I. Golovatch, Phanara Thach, Samol Chhuoy, Peng Bun Ngor, Ruttapon Srisonchai, Chirasak Sutcharit and Somsak Panha. 2020. Two New Species of the Millipede Genus Plusioglyphiulus Silvestri, 1923 from Cambodia (Diplopoda, Spirostreptida). ZooKeys. 938: 137-151. DOI: 10.3897/zookeys.938.51234