Madagascarhinus, Wesener, 2023

Wesener, Thomas, 2023, Madagascarhinus, a new genus of the family Siphonorhinidae with two new species from Madagascar (Diplopoda, Siphonophorida), Zootaxa 5278 (1), pp. 163-175 : 164-165

Madagascarhinus n. gen.

Type species: Madagascarhinus madagascariensis n. sp.

Other species included: Madagascarhinus andasibensis n. sp.

Diagnosis: Madagascarhinus n. gen. species are relatively short (<65 tergites), whitish, setose siphonorhinids with neither paranota, nor spines surrounding the ozopore. Tergites are covered with numerous wide spines, especially at the posterior margin, the ozopores are surrounded by a dense ring of setae. The first leg in males is unmodified, the coxa is fused to the sternite or stigmatic plate ( Fig. 3A ), the head is pear-shaped ( Fig. 1C ), the apical podomere of the posterior gonopod is divided into two branches lacking spines ( Fig. 3F ).

Madagascarhinus n. gen. differs from Kleruchus in the much smaller body length (11–12 mm versus 30–45 mm), segment number (61–63 versus 111–134), colour (whitish versus yellow—olive-green) and especially the first leg pair of the male, which is a regular leg in Madagascarhinus n. gen. but strongly thickened and lacking a claw in Kleruchus . Sensilla basiconica on antennomere 5 and 6 located in fields (in pits in Kleruchus ). Posterior gonopod apical podomere with two long branches with a spoon-like apex, and a third spiniform basal process (only a single branch in Kleruchus ).

Madagascarhinus n. gen. differs from Nematozonium in the much smaller segment number (61–63 versus 150–182). Sensilla basiconica on antennomere 5 and 6 are present in two or three rows and located in fields (apparently absent in Nematozonium ). Posterior gonopod apical podomere with two long branches with a spoon-like apex, and a third spiniform basal process (two branches wrapped around one another, each branch with a spine in Nematozonium ).

Madagascarhinus n. gen. differs from Illacme in the much smaller segment number (61–63 versus 130–192). It differs from Illacme in the antenna: disc with single field of sensilla basiconica and additional isolated spiniform sensilla ( Fig. 4E ) in Madagascarhinus n. gen., while there are only sensilla basiconica in Illacme . The ozopore is located more dorsally in Madagascarhinus n. gen. ( Fig. 5A ) than in Illacme , anchor-shaped projections at the posterior tergite margin are absent (present in Illacme ). Posterior gonopod apical podomere with two long branches with a spoon-like apex, and a third spiniform basal process (gonopods apically serrated with 3–5 branches, compare Fig. 3F to Marek et al. 2012: 87, fig. 6a).

Madagascarhinus n. gen. differs from Siphonorhinus , as far as their characters are known, in the posterior gonopod in ventral (posterior) view with a third, setae-like process at mid-length ( Fig. 3G ) (third process absent in Siphonorhinus ); antennomere 6 cylindrical ( Fig. 2A ), while it is greatly enlarged with a lateral inflation in Siphonorhinus ; salivary gland opening on tip of labrum ( Fig. 4F ), opposed to species of Siphonorhinus , where the opening is located close to the mandibles; sensilla basiconica on antennomere 5 and 6 in fields, while they are in slight depressions in Siphonorhinus .

Madagascarhinus n. gen. differs from the recently discovered genus from South America in the presence of sensilla basiconica on antennomere 5 (absent in the genus from South America); the ring of setae surrounding the ozopores (two short spines projecting posteriorly in the genus from South America), surface covered with large flat spines (covered by scales in the genus from South America).

Etymology: The new genus is named after its terra typica, Madagascar, with the addition - rhinus (= nose). Masculine.

Figures

FIGURE 1. Madagascarhinus n. gen. habitus. A. Madagascarhinus madagascariensis n. gen., n. sp., ♁ holotype (MHNG Mad-89/21), habitus, lateral view. B–D. Madagascarhinus andasibensis n. gen., n. sp., ♁ holotype (ZFMK MYR12218): B. Habitus, lateral view. C. Anterior body end, lateral view. D. Posterior body end, lateral view. Abbreviations: av = anal valves; Co = collum (tergite 1); Go = gonopods; L1 = leg 1; oz = ozopore; Pre = preanal ring; T63 = tergite 63. Not to scale.

FIGURE 2. Madagascarhinus madagascariensis n. gen., n. sp., ♁ paratype (ZFMK MYR12534), SEM. A. Head, lateral view. B. Head, ventral view. C. Gnathochilarium, distal part. D. Left antenna, distal view. E. Ozopore. F. Midbody ring. anterio-lateral view. G. Spiracle, ventral. H. Midbody ring, dorsal view. Abbreviations: I–VII = antennomeres, ac = apical cones, cl = claw, cx = coxa, ep = epicranium, fe = femur, fh = forehead, ge = genae, La = labrum, LL = lamella lingualis, Me = mentum, mz = metazonite, oz = ozopore, pa = palp-like structure, pl = pleurite, pof = postfemur, prf = prefemur, pz = prozonite, sb = sensilla basiconica, sp = spiracle on sternite, ssb = spiniform sensilla, st = sternite, St = gnathochilarial stipes, ta = tarsus, ti = tibia. Square highlights position of ozopore.

FIGURE 3. Madagascarhinus madagascariensis n. gen., n. sp., ♁ paratype (ZFMK MYR12534), SEM. A. Legs 1 and 2, anterior view. B. Left leg 2 with male gonopore, posterior view. C. Left midbody leg, anterior view. D. Left anterior gonopod, ventral view. E. Left anterior gonopod, posterior-lateral view. F. Posterior gonopods, posterior view. G. Posterior gonopods, anterio-lateral view. Abbreviations: a1–a7 = podomeres of the anterior gonopod, cl = claw, cx = coxa, f1 = pointed process of the posterior gonopods’ apical podomere, f2 & f3 = paddle shaped processes of the posterior gonopods’ apical podomere, fe = femur, go = gonopore/pseudopenis, p1–p7 = podomeres of the posterior gonopod, pof = postfemur, prf = prefemur, st = sternite; ta = tarsus, ti = tibia.

FIGURE 4. Madagascarhinus andasibensis n. gen., n. sp., ♁ holotype (ZFMK MYR12534), SEM. A. Head and first segments, lateral view. B. Head, ventral view. C. Head, anterior view. D. Left antenna, lateral view. E. Left antenna, view on disc. F. Mouth opening, distal view. G. Gnathochilarium, ventral view. H. Distal part of gnathochilarium. Abbreviations: I–VII = antennomeres, ac = apical cones, cl = claw, ep = epicranium, fh = forehead, ge = genae, L1 = leg 1, La = labrum, LL = lamella lingualis, md = mandible?, Me = mentum, mz = metazonite, pa = palp-like structure, pl = pleurite, pz = prozonite, sb = sensilla basiconica, ssb = spiniform sensilla, st = sternite, St = gnathochilarial stipes, ta = tarsus, ti = tibia.

FIGURE 5. Madagascarhinus andasibensis n. gen., n. sp., ♁ holotype (ZFMK MYR12218), SEM. A. Mid-body segments, lateral view. B. Ozopore. C. Mid-body-rings, dorsal view. D. Mid-body-rings, ventral view. E. Mid-body leg, anterior view. Abbreviations: cl = claw, cs = coxal sac, cx = coxa, fe = femur, mz = metazonite, oz = ozopore, pl = pleurite, pof = postfemur, prf = prefemur, pz = prozonite, st = sternite, ta = tarsus, ti = tibia, tr = trochanter.