Rotundotergum elevatum Golovatch, Bouzan & Gallo, 2022

Golovatch, Sergei I., Bouzan, Rodrigo S., Gallo, Jéssica S. & Bichuette, Maria E., 2022, A new genus and two new species of the millipede family Chelodesmidae from Bahia state, northeastern Brazil, including a likely troglobiont (Diplopoda, Polydesmida), Zootaxa 5155 (1), pp. 87-104 : 98-101

Rotundotergum elevatum Golovatch, Bouzan & Gallo , sp. nov.

Figs 8–10

Material examined. Holotype male ( LES0027945 ), Brazil, Bahia State, São Desidério Municipality, Gruta Sumidouro do João Baio cave , S12°22’27.6”, W44°53’31.7”, ca 580 m a.s.l., 2.XI.2011, M.E. Bichuette, J.E. Gallão, C.S. Fernandes & D.R. Pedroso leg.

Paratypes: 1 male, 2 subadult females ( LES0027946 ), same place, taken together with holotype .

Name. To emphasize the mostly upturned paraterga, neuter adjective in genitive case.

Diagnosis. Same as for the genus.

Description. Length of adults ca 35 mm (male holotype) or 39 mm (male paratype), width of midbody pro- and metazonae 3.0 and 4.7 mm (male holotype) or 3.1 and 5.0 mm (male paratype), respectively. Coloration mostly red-brown (male paratype), light reddish only mid-dorsally in anterior half of body (male holotype) or uniformly beige to light brown (subadult female paratypes), adults with lighter to yellowish antennae, legs, lateral calluses on paraterga, and tip of epiproct ( Figs 8 , 9A, B , & D).

Adult body with 20 rings (18p+1a+T) ( Fig. 8 ). Tegument mainly poorly shining, texture mostly leathery to finely striolate. Head poorly setose over clypeolabral region, vertex bare, epicranial suture evident ( Fig. 9C ); isthmus between antennae about as wide as diameter of antennal socket ( Fig. 8C ). Antennae relatively long and slender, poorly clavate due to only a slightly enlarged antennomere 6, in situ projecting past ring 3 dorsally (male) or 2 (subadult female); in length, antennomeres 2 = 5 = 6> 3 = 4> 1> 7 ( Fig. 8 ). Genae subquadrate laterally ( Fig. 8 ), incisura lateralis small and round, located beneath antenna ( Fig. 9C, T ); gnathochilarium without peculiarities, very densely pilose.

In width, head <ring 5=16 <collum <2=3=4 (male), body gradually tapering towards telson on rings 16–19 ( Fig. 8 ). Dorsum mostly slightly convex, generally smooth, metaterga largely very delicately striolate and rather densely microtuberculate, only caudal row of microtuberculations in front of rear tergal margin being regular ( Fig. 8 ). Surface below paraterga more clearly striolate. Paraterga very strongly developed, mostly clearly upturned and reaching the level of dorsum, smaller, lower and subhorizontal in subadult females, in adult males set high, mostly at about upper ¼ height of metazonae ( Figs 8 & 9D ), collum crescent-shaped, regularly convex at a narrowly rimmed anterior margin, slightly concave in the middle at a faintly rimmed caudal margin; following metaterga shoulder-shaped at a clearly rimmed anterior margin, metaterga 2–5 each with a very small and sharp denticle drawn laterally at a clearly angular anterolateral corner, metaterga 2–4 each with a very flat and broad lateral callus; following metaterga smooth at lateral margin, each with similarly and clearly rounded lateral margins and both more narrowly rounded anterolateral and caudolateral corners, calluses being particularly thick and prominent on pore-bearing rings, and interrupted anteriorly by a small incision behind anterolateral corner; caudal margins of paraterga narrowly rimmed much like anterior margin ( Figs 8 & 9B–D ). Caudal corners of paraterga almost sharp, beak-shaped and distinctly drawn past rear tergal margin only in rings 17–19 ( Fig. 8 ). Pore formula normal (5, 7, 9, 10, 12, 13, 15–19); ozopores small, located inside ovoid pits considerably before caudal corners of paraterga ( Figs 8 & 9D ). Tergal setae absent, no setation pattern traceable on metaterga. A weak transverse impression traceable on most metaterga. Stricture between pro- and metazonae distinct, but rather narrow, shallow and smooth (male). Limbus conspicuously brush-like ( Fig. 9B ). Pleurosternal carinae increasingly low, arcuate, longitudinal ridges or bulges traceable from ring 2 until ring 6 (male). A poor axial line sometimes traceable on metaterga of adults ( Fig. 8 ). Epiproct rather long, conical, slightly curved caudally, tip rounded; pre-apical papillae very small ( Fig. 8 ). Hypoproct subtriangular, sharpened at tip; setigerous papillae at caudal corners very small and well separated; sides faintly convex ( Fig. 8C ).

Sterna broad, without notable modifications even before ring 7, nearly glabrous, cross-impressions weak ( Fig. 8C ). Legs long and slender ( Fig. 8 ), 1.6–1.7 times as long as mid-body height, considerably shorter in subadult females; male legs without tibial chelae; in length, femur >> tarsus> tibia> prefemur = postfemur> coxa; claw short and simple ( Fig. 8 ). Male gonopores located on distinct, distomesal, coniform gonapophyses ( Fig. 8C ).

Gonopodal aperture subcordiform, much broader than following sterna, depressed caudal shelf with a few small and transverse crests ( Fig. 9B ). Gonopods ( Figs 9C, D & 10 ) stout and mostly robust, with evident sternal rudiments (st) between gonocoxae (Cx); gonocoxa devoid of a distodorsal apophysis, but supplied with a distinct and setose distolateral lobe (lo) subtending the telopodite (Te); cannula (c) as usual, a thin curved tube, devoid of setae mesally at its base; prefemoral region (Pf) as usual, short, about half as long as an untwisted acropodite (A); caudal prefemoral process (PfP) long, slender, unciform, directed unusually strongly mesad and completely separated from A ( Fig. 10 ); A laminar and membranous, suberect; seminal groove (Sg) running entirely on mesal side of Te, ending up on a spiniform solenomere (sl) branching off at A midway opposite a similarly slender and rounded acropodital process (AP), both sl and AP being equal in length ( Figs 9D & 10 ).

Remarks. Based on most or much of the body being clearly pigmented, up to red-brown, superficially this species is certainly not more than troglophilic. This only emphasizes the general impression that Chelodesmidae , however diverse and important in the fauna of Brazil, cannot be regarded as typical elements of cave biota.

Figures

FIGURE 8. Rotundotergum elevatum sp. nov., male paratype. A-C. Habitus, dorsal, lateral and ventral views, respectively. Photographs by K.V. Makarov, taken not to scale.

FIGURE 9. Rotundotergum elevatum sp. nov., male paratype. A. Incisura lateralis (I) beneath antenna, sublateral view. B. Body ring 7 with gonopods removed to show gonopod aperture, ventral view. C & D. Body ring 7 with intact gonopods, ventral and lateral views, respectively. Abbreviation: I, Incisura lateralis. Photographs by K.V. Makarov, taken not to scale.

FIGURE 10. Rotundotergum elevatum sp. nov., male paratype. A & B. Both gonopods, anterior and posterior views, respectively. C-F. Right gonopod, mesal, lateral, ventrocaudal and caudal views, respectively. Abbreviations: A, acropodite; c, cannula; Cx, gonocoxa; AP, acropodital process; lo, lateral lobe; Pf, prefemoral region; PfP, prefemoral process; sl, solenomere; st, sternal rudiment; Te, telopodite. Photographs by K.V. Makarov, taken not to scale.