Xenobolus Carl, 1919

Sankaran, Pradeep M. & Sebastian, Pothalil A., 2020, A redescription and a synonym in the South Asian millipede genus Xenobolus Carl, 1919 (Spirobolida, Pachybolidae), Zootaxa 4780 (1), pp. 165-179 : 166-167

Genus Xenobolus Carl, 1919

Diaphoropus Silvestri, 1897 (type species Iulus (recte: Julus ) carnifex Fabricius, 1775 , by original designation). Preoccupied name.

Xenobolus Carl, 1919 (type species Iulus (recte: Julus ) carnifex Fabricius, 1775 , by original designation).

Erythroprosopon Verhoeff, 1936 (type species Erythroprosopon phoenix Verhoeff, 1936 , by monotypy). Synonymised by Hoffman (1962).

Diagnosis. Medium-sized, colourful pachybolid ( Fig. 1A, B ): male and female nearly equal in length and thickness. Mature individuals with 50 body rings. No apodous rings in front of telson ( Fig. 2C, E ). Scobinae absent. Tarsal pads on male legs lacking. Body ring 6 in males greatly enlarged ventrally, protecting the gonopod pouch ( Fig. 2A ). Anterior gonopods massive ( Fig. 5A, B ), not completely retractable into pouch; sternite with a median process ( Figs 5A , 6A ); coxite anteriorly with a slender mesal process ( Figs 5A, B , 6A, B ); telopodite anteriorly with a narrow mesal process ( Figs 5A, B , 6A, B ). Posterior gonopods with a narrow sternite ( Fig. 6E ); coxite unmodified; telopodite consisting of two branches, both bent mesad ( Figs 5C, D , 6D, E ), main branch with an apical fringe directed towards mesal branch ( Fig. 6 D–F), mesal branch anteriorly with lateral processes ( Fig. 6 D–F). Neither membranous folds nor a connection between mesal and main branches ( Fig. 6D ).

Relationship. Carl (1919) treated Xenobolus as a member of Trigoniulidae Attems, 1909 and related it with Trigoniulus Pocock, 1894 . Verhoeff (1936) included Xenobolus in Spiromimidae Brölemann, 1913 . Hoffman (1962), who rejected both of these views, proposed its inclusion in the Pachybolidae and suggested informally a close relationship with Stenobolus Carl, 1918 and Mystalides Attems, 1910 (now a synonym of Aphistogoniulus Silvestri, 1897 ). A recent phylogenetic treatment based on morphological characters alone suggested a relationship of Xenobolus with the Malagasy genus Spiromimus de Saussure & Zehntner, 1901 (Wesener & Enghoff 2009). Even though Xenobolus was found to be sister to Spiromimus , these authors hesitated to accept its inclusion in Spiromiminae Brölemann, 1913 and argued that both these genera were close.

Subfamily inclusion. Currently Xenobolus is not assigned to any of the four subfamilies of Pachybolidae viz., Centrobolinae Hoffman, 1980 , Pachybolinae , Spiromiminae and Trigoniulinae Attems, 1909 ( Wesener et al. 2008). Irrespective of its weak relationship with Spiromimus, Wesener and Enghoff (2009) excluded it from Spiromiminae .

Species included. Only Xenobolus carnifex ( Fabricius, 1775)

Figures

FIGURE 1. Field photographs of Xenobolus carnifex (Fabricius, 1775). A: Male from Pullodu in Trippalur, Palakkad (MILLI- ADSH0007). B: Female from Pullodu in Trippalur, Palakkad (MILLI-ADSH0007). Photo courtesy Jimmy Paul.

FIGURE 2. Xenobolus carnifex (Fabricius, 1775) (MILLI-ADSH0007). A, D: Head and anterior trunk segments, lateral view. B: Legs 1–7, ventral view. C, E: Telson, lateral view. F: Left antenna, lateral view. G: Gnathochilarium, ventral view.A–C, F–G male, D–E female. Scale bars: A–B, D–E = 2 mm; C = 1 mm; F–G = 0.5 mm.

FIGURE 5. Xenobolus carnifex (Fabricius, 1775) (MILLI-ADSH0007), male. A: Anterior gonopods, ventral view. B: Same, dorsal view. C: Posterior gonopod, ventral view. D: Same, dorsal view. Scale bars: A–D = 1 mm.

FIGURE 6. Xenobolus carnifex (Fabricius, 1775) (MILLI-ADSH0007), male. A: Anterior gonopods, ventral view. B: Same, dorsal view. C: Same, mesal view. D: Telopodite of left posterior gonopod, ventral view. E: Left posterior gonopod, dorsal view. F: Enlarged view of distal part of left telopodite, dorsal view. Abbreviations: A = apodeme, cRT = conical process of retrorse process, CO = coxite, gT1 = first globular process of telopodite, gT2 = second globular process of telopodite, hMsB = hook-like process of mesal branch, lmMsB = lamellate process of mesal branch, mCO = mesal process of coxite, MnB = main branch, MsB = mesal branch, msST = median spatula-shaped process of sternite, RT = retrorse process, ST = sternite, tMsB = trapezoid process of mesal branch. Digit 1 claw-shaped mesal process, 2 branched process, 3 conical process. Scale bars: A–C, E = 1 mm; D, F = 0.5 mm.