Genus

Rhopalomeris Verhoeff, 1906: 188 (D).

Rhopalomeris – Silvestri 1917: 140 (D); Jeekel 1971: 17 (L); Mauriès 1971: 435 (M); 2007: 243 (M); Hoffman 1980: 68 (L); Golovatch et al. 2011: 1 (D); Golovatch and Semenyuk 2016: 413 (D, K); Nguyen et al. 2019: 292 (D, K); 2021: 259 (D).

Diagnosis.

The genus Rhopalomeris could be recognized through numerous apical sensory cones on the antennal tip, and antennomere 6 being particularly enlarged and rather strongly curved. In addition, the posterior telopods are rather strongly enlarged and stout, supplied with both prefemoral and femoral trichosteles. The femur has a distinctive and particular distocaudal process. The body is relatively large, with adults ranging from 11 to 20 mm in length. The body coloration is variable, but often useful for species identification.

Type species.

Glomeris carnifex Pocock, 1889, fixed under Art. 70.3 (ICZN 1999) in Golovatch et al. (2011), misidentified as Rhopalomeris bicolor (Wood, 1865) in the original designation by Verhoeff (1906).

Other species included.

Rhopalomeris monacha Silvestri, 1917; R. tonkinensis Silvestri, 1917; R. variegata Golovatch & Semenyuk, 2016; R. sauda Nguyen, Sierwald & Marek, 2019; and R. nagao Nguyen, Nguyen & Eguchi, 2021.

Remarks.

The genus Rhopalomeris was originally typified by Verhoeff (1906) through the designation of Glomeris bicolor Wood, 1865 as the type species. However, this designation was based on specimens from Salanga Island (presently known as Phuket Island, Thailand) housed in the Berlin Museum (currently Museum für Naturkunde Berlin; ZMB), and these specimens had been previously identified by F. Karsch as G. bicolor. Although the type locality of G. bicolor is in Hong Kong (Wood 1865), Verhoeff (1906) followed Karsch’s identification, and refrained to introduce a new name to those specimens.

Furthermore, Verhoeff (1906) compared the specimens from Phuket Island with G. carnifex, noting that several characteristics were similar to his specimens. He admitted that both might be two distinct species because of possible distinctions in telopods and the number of apical sensory cones on the antennae. Verhoeff also suggested to reclassify G. carnifex under the genus Rhopalomeris.

Subsequently, Silvestri (1917) examined relevant material probably housed in the Zoological Survey of India, (formerly the Indian Museum). He synonymized G. bicolor sensu Verhoeff (1906) with R. carnifex var. pallida (Pocock, 1889) from Elphinstone Island, Mergui Archipelago, Myanmar, and redesignated R. carnifex from Tenasserim, Myanmar, as the type species.

Finally, Golovatch et al. (2011) studied the specimens of G. bicolor sensu Verhoeff (1906), from Salanga Island housed in the ZMB, and confirmed the identification of these specimens as R. carnifex. Golovatch et al. (2011) also synonymized the variety pallida with R. carnifex given the reason that the variety pallida was simply a color morph of R. carnifex, and validated that R. carnifex is the type species of Rhopalomeris, fixed under Art. 70.3 (ICZN 1999). Therefore, the millipede genus Rhopalomeris is currently known only from Myanmar, Thailand, Malaysia, and Vietnam, with a total of six nominal species involved (Fig. 1).

Peplomeris was originally described as a subgenus of Rhopalomeris (Silvestri, 1917). However, it was later raised to a genus level by Mauriès (1971), who assigned this genus to the tribe Haploglomerini, whereas Rhopalomeris belongs to the tribe Trachysphaerini (Mauriès, 1971). Nguyen et al. (2019) provided a comprehensive comparison among these two genera, highlighting key morphological differences among five Vietnamese glomerid genera. Peplomeris is characterized by simple, elongated telopods, the presence of a prefemoral trichostele, and a reduced to missing femoral trichostele. In contrast, Rhopalomeris has antennomere 6 that is unusually large, and trichosteles present in both prefemur and femur of the telopods. The antennae of Rhopalomeris also have numerous apical sensory cones like in Peplomeris.