Ribautia combinata, Pereira, Luis A., Uliana, Marco & Minelli, Alessandro, 2006

Pereira, Luis A., Uliana, Marco & Minelli, Alessandro, 2006, New species and new records of the genus Ribautia Brölemann, 1909 (Chilopoda: Geophilomorpha: Geophilidae) from South America, Zootaxa 1106, pp. 45-68 : 47-55

Ribautia combinata n. sp.

( Figs. 1–29 )

Diagnosis: This is the only species of Ribautia having in each coxopleuron an anterior coxal organ with independent opening and 4–5 additional coxal organs grouped in one posterior cluster. Of the other Neotropical species in this genus, those most similar to Ribautia combinata n. sp. are R. limaensis Kraus, 1957 and R. silvana Kraus, 1954 . Differential characters are shown in table 1.

Type material examined: Holotype Ψ, 55 pairs of legs, body length 9 mm, from Peru: Loreto: Allpahuayo ca. 30 Km S Iquitos, Terra firme, primary tropical rainforest, 26.III.1998, S. I. Golovatch leg. ( MNHL).

Etymology: The specific epithet refers to the coxal pores of this species, which combine characteristics hitherto accepted as discriminating between Schizoribautia and Ribautia s.str. (see Introduction).

Description of Ψ holotype. 55 pairs of legs, body length 9 mm, maximum body width 0.5 mm. Colour (of preserved specimen in alcohol) yellowish.

Antennae ca. 2.4 times as long as the cephalic plate, distally slightly attenuate; all articles (except the first) longer than wide. Setae on a.a. I to V–VI few and of different length, those of remaining articles progressively shorter and more numerous towards the tip of the appendage ( Fig. 1 ). Terminal a.a. with ca. 11 claviform sensilla on the external border and ca. 10 on the internal border ( Fig. 2 ). Distal end of this a.a. with ca. three very small specialised sensilla apparently not split apically ( Fig. 2 ). Dorsal and ventral surface of a.a. II, V, IX and XIII with very small specialised sensilla. On the ventral side these sensilla are restricted to an internal latero­apical area and occur in two different types: a and b. Type a sensilla are very thin and not split apically, type b sensilla are thicker and very similar to those on the distal end of the terminal a.a. (a, b, Fig. 3 ). Specialised sensilla on dorsal side are restricted to an external latero­apical area and of three types: a and b, respectively similar to a and b of ventral side, and type c sensilla, similar to type b but smaller and with a small dark 'root' (a, b, c, Fig. 5 ). Distribution of sensilla as in table 2.

Cephalic plate approximately rectangular but sides curved, distinctly longer than wide (ratio 1.5:1), shape and chaetotaxy as in Fig. 6 .

Clypeus with four setae on the clypeal area; middle part with four setae of similar size ( Fig. 7 ). Surface of clypeal area very densely reticulated ( Fig. 8 ).

Labrum: mid­piece well­developed, sclerotised, with ca. 17 short, round­pointed teeth on the middle and 2+3 long hyaline filaments on the sides. Side­pieces with 4+5 long hyaline filaments ( Fig. 9 ).

Mandible: pectinate lamella with ca. 17 hyaline teeth ( Fig. 10 ).

First maxillae without lappets on coxosternum; telopodites with rudimentary lappets ( Fig. 11 ). Coxosternum without setae; median projections of coxosternum subtriangular, well developed, with 4+5 setae of different length. Article II of telopodite with 3+3 ventral setae and 2+2 dorsal setae ( Figs. 11–12 ).

Second maxillae: coxites with 5+5 setae, joined medially only by a non­areolate membranous isthmus ( Fig. 12 ). Telopodites with setae of uniform thickness, relative size of apical claw as in Fig. 12 . Process of antero­internal corners of coxosternum well developed ( Fig.13 )

Forcipular segment: when closed, telopodites project slightly beyond the level of the anterior margin of the head. Basal plate with an irregular transverse row of six large setae near the posterior margin, a few smaller setae dispersed on the remaining surface. Coxosternum with incomplete chitinous lines. Telopodites: trochanteropraefemur with a conspicuous, subtriangular and slightly pigmented apical tooth on the medial edge; femur and tibia without teeth; tarsungulum with a well­developed, slightly pigmented basal tooth; dorsal and ventral edges of the ungular blade not serrulate ( Figs. 14–15 ). Calyx of poison gland as in figure 15; chaetotaxy of coxosternum and telopodites as in figure 14.

Walking legs: pairs I to IX–X with setae of different thickness ( Figs. 16–17 ), remaining legs with setae of uniform thickness ( Fig. 18 ). Claws ventrobasally with an anterior and a posterior parunguis ( Fig. 19 ).

Sterna: pore fields present from the second to the antepenultimate sternum. All fields undivided. Form of fields changing along the trunk as in Figs. 20–26 . Number of pores on selected sterna: on sternum II, 13 pores; on III, 24; on VII, 29; on XLIII, 11; on XLVII, 3; on LII, 23; on LIII, 26.

Last leg­bearing segment without pleurites at the sides of praetergum. Praesternum not divided along the sagittal plane; form and chaetotaxy of tergum and sternum as in Figs. 27–28. Coxopleura slightly protruding at the ventral distal end; setae small and numerous on internal distal edge, remaining surface with few larger setae. Each coxopleuron with an anterior independent coxal organ and a posterior cluster of ca. 5–6 coxal organs, both opening on the membrane between coxopleuron and sternum and covered by the latter ( Figs. 28–29 ). Last legs with seven podomeres, shape and chaetotaxy as in Figs. 27–28. Praetarsus unguiform, smaller than those of the preceding legs.

Terminal segments: intermediate tergum with posterior margin convex, intermediate sternum seemingly covered by the sternum of the last leg­bearing segment, first genital sternum as in Fig. 28 . Anal organs present.

ɗ. Unknown.

Barbieri, 1995, R. onycophaena Pereira, Foddai & Minelli, 2000 , R. rossi Chamberlin, 1957 and R.

tropica (Brölemann, 1898) .

Figures

FIGURES 1 – 6. Ribautia combinata n. sp. Ψ holotype (Peru: Loreto: Allpahuayo, ca. 30 Km S Iquitos): 1, left antenna, ventral; 2, apical region of left a. a. XIV, ventral; 3, left a. a. V, ventral (a, b: type a, b sensilla); 4, left a. a. V, dorsal (a, b: type a, b sensilla); 5, left a. a. IX, dorsal (a, b, c: type a, b, c sensilla); 6, cephalic shield.

FIGURES 7 – 12. Ribautia combinata n. sp. Ψ holotype (Peru: Loreto: Allpahuayo, ca. 30 Km S Iquitos): 7, clypeus and basis of antennae; 8, clypeal area; 9, labrum; 10, mandible; 11, left first maxilla, dorsal; 12, first and second maxillae, ventral.

FIGURES 13 – 17. Ribautia combinata n. sp. Ψ holotype (Peru: Loreto: Allpahuayo, ca. 30 Km S Iquitos): 13, detail of process of antero­internal corner of coxosternum of left second maxilla, ventral; 14, forcipular segment with poison claws, ventral; 15, detail of poison gland in right poison claw, ventral; 16, right leg I, postero­ventral; 17, right leg II, ventral.

FIGURES 18 – 26. Ribautia combinata n. sp. Ψ holotype (Peru: Loreto: Allpahuayo, ca. 30 Km S Iquitos): 18, right leg XV, ventral; 19, claw of right leg I, postero­ventral; 20 – 26, sterna II, III, VII, XLIII, XLVII, LII, LIII.

FIGURES 28 – 29. Ribautia combinata n. sp. Ψ holotype (Peru: Loreto: Allpahuayo, ca. 30 Km S Iquitos): 28, last leg­bearing segment and terminal segments, ventral; 29, detail of coxal organs, ventral.