Rupidesmus Schubart, 1952

Bouzan, Rodrigo Salvador, Iniesta, Luiz Felipe M. & Brescovit, Antonio Domingos, 2018, A review of the millipede genus Rupidesmus Schubart, 1952 (Polydesmida: Chelodesmidae), Zootaxa 4434 (3), pp. 589-599 : 590-591

Genus Rupidesmus Schubart, 1952

Rupidesmus Schubart, 1952: 447 –454. Type species: Rupidesmus ruber Schubart, 1952 , by original designation. Hoffman, 1980: 155.

Genus diagnosis: Males of Rupidesmus differ from those of other chelodesmid genera by the combination of the following characters. A pair of ventral projections present on the sternite of the fifth body ring ( Figs 5D , 6D ), as also noted in Leptodesmini (Leptodesmus DeSaussure s. str., Drepanodesmus Hoffman and Dialysogon Hoffman ), where they are present on sternites of fourth and sometimes sixth body ring. Legs with a rounded ventral-apical process on the prefemur and an acute apical-ventral membranous projection on the tibia ( Figs 5C , 6A–C ), as in Sandalodesmus Silvestri (Sandalodesmini) and Leptodesmini . Male gonopodal characters: prefemoral process dagger-shaped; notably shortened, about 1/3 of the length of the acropodite ( Fig. 4D ). Massive acropodite with a conspicuous indentation in the posterior margin (visible in mesal view; Figs 3A, D , arrows). The reduction of the prefemoral process is also present in some species belonging to genus Obiricodesmus Schubart (Cornalatini) , but with a shorter acropodite than in Rupidesmus .

Genus description: General characters: Body length between 60.6 mm ( R. ruber ) and 72.5 mm ( R. aclys n. sp.). Coloration (specimens long preserved in 70% ethanol) variable between species, ranging from reddish to light brown. Head ( Fig. 1A ) with row of around 50 labral setae, 30 clypeo-labral setae and 10 clypeal setae ( Fig. 1B ), shape of the incisura lateralis suboval ( Fig. 1C ). Antennae: seventh antennomere with two large invaginations between the two pairs of apical sense cones ( Figs 1D–E ). Body rings: integument smooth, without setae. Collum: anterior border arched and posterior border slightly concave ( Figs 2A, D ). Stigma oval. Sternite of fifth body ring with a pair of ventral projections ( Figs 5D , 6D ). Ozopore situated on posterior edge of paranota. Ozopore arrangement: 5, 7, 9, 10, 12, 13, 15–19 (following the normal polydesmidan pore formula); ozopores surrounded by peritremata. Paranota: prominent and long, wide and nearly horizontal, straight on posterolateral sides, covering part of the legs, without setae on the edges. Paranota form: anterior corners rounded, posterior edges sub-triangular ( Figs 2B, E ). Legs: with rounded ventro-apical process on the prefemur and with acute apical-ventral membranous projection on the tibia ( Figs 5C , 6A–C ), these structures are present in all pairs except the last. Telson: triangular ( Figs 2C, F ), with five pairs of macrosetae on the dorsal side and two pairs (spinnerets) in the apical region.

Male characters: Gonopore: located on the coxae of the second leg-pair, coxae rectangular, with an apical pore. Gonopod aperture on seventh body ring: transversely oval, large; posterior edge without folds ( Figs 5E , 6E ). Gonopods: gonopod coxae ( Figs. 4A, B ) prominent, equivalent to about half the length of the telopodite, with a large spiniform process ( Fig. 4C ). Cannula ( Fig. 4A ): hook-shaped. Prostatic groove ( Fig. 4A ): runs almost entire length of acropodite along mesal side. Telopodite ( Fig. 4A ): elongate and inclined, divided into prefemoral region and acropodite region ( Fig. 4A ). Prefemoral process: shorter (about 1/3 of the length of the acropodite), stout and shape resembling a dagger ( Fig. 4D ). Acropodite robust with an indentation at the posterior margin and ending in acute apex ( Fig. 4F ).

Female characters: Known only for R. ruber . Cyphopods: oval-shaped, situated directly behind the second pair of legs on the third body ring; composed of three valves, all well-covered with setae; two valves joined by a membrane, with a third apically, appressed against both larger valves ( Figs 5A–B ).

Distribution: Known only from the state of Minas Gerais, Brazil, occurring in the limestone karst area of the Bambui Group and the “Iron Quadrangle” (Quadrilátero Ferrífero) iron-ore area ( Fig. 7 ).

Composition: Rupidesmus ruber Schubart, 1952 and R. aclys n.sp.

Figures

FIGURE 1. Structures of Rupidesmus (IBSP 2865). A, dorsal surface of the head of the genus; B, detail of labrum; C, detail of incisura lateralis; D, antennae in lateral view; E, detail of the last antennomeres. Scale bars: A) 2 mm.; B) 1 mm.; C) 200 µm; D) 1 mm.; E) 500 µm. Abbreviations: Ls, labral setae; Cls, clypeo-labral setae; Cs, clypeal setae.

FIGURE 2. Dorsal views of anterior (A, D), midbody (B, E) and posterior (C, F) body rings of Rupidesmus ruber (holotype, MZSP 996) (A–C) and Rupidesmus aclys n. sp. (holotype, IBSP 2890) (D–F). Scale bar: 2 mm.

FIGURE 3. Rupidesmus ruber (holotype, MZSP 996), left gonopod. A, mesal view; B, lateroventral view; C, ectal view. Rupidesmus aclys n. sp. (IBSP 2890), left gonopod. D, mesal view; E, lateroventral view; F, ectal view. Scale bars: 1 mm. Abbreviations: AP, acropodital process; PfP, prefemoral process; PG, prostatic groove; SP, spiniform projection on gonopod coxae. Arrows refer to the indentation at the posterior margin of the acropodite.

FIGURE 4. Rupidesmus ruber (IBSP 2865). A, left gonopod in mesal view; B, left gonopod in ectal view; C, detail of coxal apophysis; D, detail of prefemoral process; E, indentation at the posterior margin of the acropodite; F, detail of the apical portion of acropodite. Scale bars: A) 1 mm.; B) 1 mm.; C) 300 µm; D) 200 µm; E) 300 µm; F) 200 µm. Abbreviations: AP, acropodital process; A, acropodital region; C, cannula; Cx, coxa of gonopod; Pf, prefemoral region; PfP, prefemoral process; PG, prostatic groove; SP, spiniform projection on gonopod coxae; T, telopodite.

FIGURE 5. Rupidesmus ruber. A, right cyphopod in ventral view; B, left cyphopod in lateroventral view (IBSP 4653); C, leg (8 th leg pair) in lateral view; D, sternite of body ring 5 in dorsal view; E, aperture of gonopod; F, sternite on body ring 8 (MZSP 996). The arrows point to the pairs of projections of the sternite on body ring 8. Scale bars: A) 500 µm; B) 400 µm; C) 1 mm.; D) 1 mm.; E) 1 mm.; F) 1 mm. Abbreviations: EV, external valve; Op, operculum; IV, internal valve; VaP, ventro-apical process; MP, membranous process.

FIGURE 6. Rupidesmus aclys n. sp. (holotype, IBSP 2890). A, leg (8 th leg pair) in lateral view; B, detail of prefemur, ventroapical process; C, detail of tibia, apico-ventral membranous projection; D, sternite of body ring 5 in dorsal view; E, aperture of gonopod; F, sternite on body ring 8. The arrows point to the pairs of projections of the sternites on body ring 8. Scales bars: 1 mm. Abbreviations: VaP, ventro-apical process; MP, membranous process.

FIGURE 7. Distribution maps of Rupidesmus species. A, Brazil; B, Minas Gerais state, with karst formations marked by different colors. C, detail of the area between the limestone karst Bambui Group and the iron-ore area “Iron Quadrangle”. Circles: R. ruber; triangle: R. aclys n. sp.