Eumastigonus Chamberlin, 1920

Korsós, Zoltán & Johns, Peter M., 2009, Introduction to the taxonomy of Iulomorphidae of New Zealand, with descriptions of two new species of Eumastigonus Chamberlin, 1920 (Diplopoda: Spirostreptida: Epinannolenidea), Zootaxa 2065, pp. 1-24 : 4-8

Genus Eumastigonus Chamberlin, 1920

Eumastigonus Chamberlin, 1920: 62 ; Jeekel 1970: 09; Hoffman 1972: 200; Mauriès 1983: 256; 1987: 198; Shelley 2003: 196.

Dimerogonus Attems, 1903 partim. Verhoeff 1924: 74, 82.

Insulocambala Verhoeff, 1944: 31 ; Hoffman 1972: 200.

Diagnosis: An epinannolenidean genus with modified first male legpair, and with well-developed flagellum in anterior male gonopods. Anterior gonopods with strong, hairy or pectinate coxal and telopodal processes which form sheath around straight and slender posterior gonopods.

Type species: Eumastigonus kaorinus Chamberlin, 1920 by original designation.

Other included species: E. insulanus ( Attems, 1903) , E. ater , E. distinctior , E. maior , E. parvus (all Chamberlin, 1920), E. hemmingseni Mauriès, 1983 , and E. hallelujah sp. n., E. waitahae sp. n.

Description: Size: Length from 15 up to 80 mm, maximum midbody diameter between 1.4–4.5 mm, number of podous rings: 30–59, with 0–4 apodous, and telson.

Head as in Fig. 5 ; gnathochilarium generalized epinannolenidean type (cf. with Fig. 4 , see also Jeekel 1985) where mentum and promentum separate; mentum large, trapezoid, widely separating gnathochilarial stipites from each other; promentum undivided, large, triangular, separating laminae linguales which contact each other at their tips, with two setae each, close to the mouth opening. Gnathochilarial stipites widening and slightly bulging frontally, with two setae along their anterior margins and more on their basal parts; in males with pair of gnathochilarial pits (gp) each with one short seta, whose function is probably sensory. Posterior surface of gnathochilarial stipites and mentum rugose, but with a smooth half-circle centrally. Gular (hypostomal) plate in males with two lateral depressions (probably for the anterior projections of the first legpair to fit in). Mandibular stipites in males slightly widening. No frontal setae.

Ocelli (10-45) usually in 2-5 rows or irregularly arranged in a rectangular, oval, triangular or almondshaped ocellarium, posterior row parallel with anterior margin of collum. Antenna generally short, antennomeres 2–6th subequal in length, 1st and 7th shorter, small, with four apical sensory cones.

Collum smooth, or with three or four weak marginal furrows on its lateral anterior corner; prozonae with irregular lines, whereas metazonae with longitudinal sutures, but only in the ventral third of the segmental part below ozopores. No metazonal setae.

Ozopores only from 6th ring caudad, behind vertical segmental suture, usually small, inconspicuous, and in some cases hardly detectable on preserved specimens.

Telson invariably without projection, paraprocts rounded, smooth, hairless, or 2+2 setae along the margin of anal opening, or rarely (in one species) entirely densely setose.

Colouration: Typically uniformly dark or lighter brown, but sometimes with characteristic colour pattern: interocular region, collum anteriorly and laterally, and telson with dark brown markings, prozonae dark, metazonae, paraprocts and legs lighter. Terga sometimes with dark middorsal stripe or series of dark middorsal spots, accompanied by two longitudinal light stripes, or one wide middorsal light stripe with two dark parallel longitudinal stripes, or dorsum generally dark brown, sides below ozopores lighter.

Male sexual characters: Mandibular stipites strongly widening, trapezoidal, their ventral sides not sclerotized, slightly swollen. Gnathochilarial stipites anteriorly with one sensory pit each in a seemingly soft, slightly swollen field. 1st legpair modified, short, stout, generally hidden between head and 2nd legpair, coxa fused with sternum (coxosternum), anteriorly provided with setae at the margin, prefemur short and wide, twice as wide as long, with two anterior blunt processes whose function is unknown (but Krabbe (1979) suggested a clasping role during mating for similar processes in Spirostreptidae ), femur almost normal, its length twice its width, mesal side straight, lateral side strongly concave, three apical podomeres (postfemur, tibia, and tarsus) subsimilar to each other, small, subequal in lengths and widths, tarsus without (or occasionally with) claw (Fig. 13).

Penis closely behind 2nd legpair, deeply bifurcated, with two long apical branches, reaching almost to the end of prefemur, tips tube-like with hairy openings.

Protrusion on 7th ring variable, sometimes glabrous and simple, in other cases rugose and significantly protruding, hence protecting the gonopods which emerge slightly between them.

Legpairs before and behind gonopodal ring with or without tarsal or femoral pads.

Gonopods: Anterior gonopods: sternum forming a strong, bilobed plate in anterior view; coxal processes long, promerite-like, each with one inner process and one or two marginally hairy or pectinate, median and/or lateral lobes or processes. Telopodite caudo-basally with a field of spine-like setae. All these lobes or processes form an envelope into which the posterior gonopod is accommodated; flagellum long, welldeveloped, curving into a groove on posterior gonopods but then, together with them, comes back in between the processes of the anterior gonopods; posterior gonopods slender, long, more simple, usually with hairy coxal knob and thin, bent lamella (telopodite) at tip.

Female sexual characters: Vulvae embedded behind 2nd pair of legs in 3rd ring, relatively large, strongly flattened, disk-shaped, valves of bursa closely pressed against each other. Operculum small, narrow, situated anterio-laterally, tightly attached to bursa, thus whole vulva is very compact. Bursal valves with or without marginal hairs. Apodematic tube and ampulla could not be observed.

Distribution: New Zealand. Estimated to include about 30 species altogether. Some species are widespread, whereas others have restricted distributions.

Remarks: The group of spines on the posterior surface of the telopodite of the anterior gonopods can be considered as the remnant of the second telopodomere. Enghoff (1985, 1991) noticed a similar structure on the posterior gonopods of certain Nemasomatoidea (cf. Fig. 42 ss in Enghoff 1985, or Fig. 22 f in Enghoff 1991). Nemastomatoids are considered to be close to the groundplan of Julida , and Iulomorphidae to the groundplan of Epinannolenidea, so this character can be seen as a possible symplesiomorphy.

Figures

FIGURES 4 – 9. Eumastigonus kaorinus. 4: Gnathochilarium of paratype female (MCZ 4868), ventral view, 5: head of holotype male (MCZ 4867), left lateral view, 6: first male legpair, posterior view, 7: anterior gonopods, anterior view (c = coxa, m = median lobe), 8: right gonopods, right lateral view, posterior gonopod removed from embrace of anterior ones, flagellum omitted (tp = telopodite process), 9: posterior gonopods, posterior view (a = apex). Scales 4 – 5: 1 mm, 6 – 9: 0.5 mm.

FIGURES 40 – 43. E. waitahae male from Okuku Pass, Canterbury Region. 40: Anterior gonopods, anterior view (tp = telopodite process, i = inner lobe, n = needle-like tip, st = sternal plate), 41: anterior gonopods, posterior view (tp = telopodite process, n = needle-like tip of inner lobe), 42: posterior gonopods, anterior view (sg = seminal groove, tp = telopodite, c = coxa, st = sternal plate, a = apex), 43: posterior gonopods, posterior view. Scales 0.5 mm.

FIGURES 22 – 24. Female vulvae (op = operculum). 22: E. kaorinus from Whangaruru headland, Northland Region, right vulva, anterior view, 23: E. distinctior from Porirua, Wellington Region, Galathea Expedition, 1951 (ZMUC), left vulva, posterior view, 24: E. hemmingseni from Akatarawa, Wellington Region, right vulva, posterior view. Scales 0.5 mm.