| Dichromatobolus elephantulus Wesener, 2020|
A new genus, Dichromatobolus gen. nov., belonging to the genus-rich mainly southern hemisphere family Pachybolidae of the order Spirobolida, is described based on Dichromatobolus elephantulus gen. et sp. nov., illustrated with color pictures, line drawings, and scanning electron micrographs. The species is recorded from the spiny bush of southwestern Madagascar. Dichromatobolus elephantulus gen. et sp. nov. shows an unusual color pattern, sexual dichromatism with males being red with black legs and females being grey. Males seem to be more surface active, as mainly males were collected with pitfall traps. Females mainly come from the pet trade. The body of this species is short and very wide, being only 8 times longer than wide in the males. Live observations show the species is a very slow mover, digging in loose soil almost as fast as walking on the surface. The posterior gonopods of Dichromatobolus gen. nov. are unusually simple and well-rounded, displaying some similarities to the genera Corallobolus Wesener, 2009 and Granitobolus Wesener, 2009, from which the new genus differs in numerous other characters, e.g., size, anterior gonopods and habitus. Despite several attempts with fresh tissue samples and different primers, molecular barcoding did not work for Dichromatobolus gen. nov. Any relationships to the other 15 genera of Pachybolidae indigenous to Madagascar remain unknown.
Keywords: biodiversity, Mahafaly Plateau, spiny forest, sexual color dimorphism, soil arthropod
Class Diplopoda de Blainville in Gervais, 1844
Order Spirobolida Cook, 1895
Family Pachybolidae Cook, 1897 sensu Hoffman 1980
Dichromatobolus gen. nov.
Diagnosis: Massive, short, differs from all other known genera of Pachybolidae in mature males being only eight times longer than wide. Coloration uniquely differing between sexes, females grey, males red (Fig. 1A). Transverse ridge on mentum of gnathochilarium absent (Fig. 4A). Male legs with tarsal pads and unusually spinose tarsi (Fig. 4D). Shares anterior telopods with apical process of telopodite (Fig. 4E–F) with Zehntnerobolus Wesener, 2009, from which Dichromatobolus gen. nov. differs strongly in habitus and posterior gonopods. Simple, apically swollen posterior gonopods (Fig. 5A–C) are shared with Corallobolus Wesener, 2009, from which Dichromatobolus gen. nov.differs in habitus and anterior telopods.
Etymology: After the differences in the color pattern between the sexes, and ʻ-bolusʼ, a common suffix for genus names of the Spirobolida. Masculine.
Taxonomic position: The posterior gonopods being connected by a sclerotized sternite as well as the absence of apodemes on the anterior gonopods (Fig. 4E–F) place Dichromatobolus gen. nov. in the suborder Trigoniulidea Attems, 1909, family Pachybolidae. The closest relative of Dichromatobolus gen. nov. is unknown.
Remarks: There is a second potential species, > 100 mm in length, with specimens from Manongarivo, Ananambao (FMNH-INS 56254), all unfortunately female. Their wide body with short legs and grey color (all other larger Spirobolida genera on Madagascar are black/red, Wesener et al. 2009) might indicate a relationship to Dichromatobolus gen. nov.
Dichromatobolus elephantulus gen. et sp. nov.
Diagnosis: Body 60–80 mm long, massive, bulky spirobolidan. Epiproct not projecting. Males red, females grey, ozopore openings in both sexes marked by a black circle. Males with tarsal pads, coxa projections absent. Legs and antennae short. Anterior gonopods, telopodite process well-developed and at apex curved laterally. Posterior gonopod slender and elongated, telopodite simple, rectangular, apically with opening of efferent duct.
Etymology: Elephantulus, diminutive noun in apposition, after the resemblance to an elephant in the female grey color, as well as a hint referring to the width of the species.