New geNera for two poorly-kNowN millipeds from Bahia (polydesmida: Chelodesmidae)

Two chelodesmid millipeds described by Brölemann (1903) from the interior of Bahia have not been reported for over 100 years despite their large size and bright coloration. Originally described as Leptodesmus gounellei and Leptodesmus carminatus, neither species is referable to Leptodesmus as currently defined nor any other established genus. Both have been studied from the type specimens, and are here designated the type species of two new genera, Plectrogonodesmus for gounellei and Baianassa for carminatus. Diagnostic characters are illustrated for both taxa. Intergeneric relationships are at present not evident, and are not suggested pending better understanding of the chelodesmid fauna of eastern Brazil. Key-Words: Diplopoda; Polydesmida; Chelodesmidae; New genera; Brazil: Bahia.


IntroductIon
Prior to about 1934, when Otto Schubart emigrated to Brazil from Germany and began to study the diverse fauna of Neotropical millipeds, the great majority of species now referred to the family Chelodesmidae had been described in a genus Leptodesmus, an ensemble of appalling heterogeneity.As he studied numerous collections from many parts of Brazil, Schubart quickly appreciated the great variety of the endemic chelodesmid fauna, and proposed no fewer than 23 new generic names to reflect the structural variability of these animals.
During this period of taxonomic refinements, Schubart was generally concerned with the placement of new species that came to his attention, and less involved with clarification of species described in Leptodesmus by European authors as far back as 1859 (nor was it always easy to borrow type specimens from European museums).As a result, a substantial number of enigmatic taxa were by default more or less bypassed and continued to infest the literature.
One major fundamental problem unresolved during Schubart's investigations concerned the characteristics and status of Leptodesmus itself.The name was originally proposed (DeSaussure, 1859) as a subgenus of Polydesmus, and contained five species only two of which were chelodesmids.One of them, P. (L.) carneus DeSaussure, 1859, was designated type of Leptodesmus by Pocock in 1909, but how the genus was to be defined in the light of future information was not addressed until Hoffman (1971) on the identity of Leptodesmus.At that time my provisional diagnosis admitted 21 species sharing several traits in gonopod structure.
The consequence of that exclusive delimitation was to leave the great majority of names proposed in Leptodesmus (ante Schubart) "homeless" in the sense of not being referable to any established generic taxon.
Having had the opportunity to study type material of many such orphans in the Brazilian fauna, I have on several occasions been able to clarify their identify and status, and now wish to call attention to two species described by Brölemann (1903) from Bahia, and to my knowledge not reported, aside from inclusion in lists, for 108 years.Since the abundance of unstudied material now available is offset by the paucity of qualified taxonomists, progress can only be piecemeal and opportunistic.While such an approach is certainly not the optimal way to an adequate comprehension of any taxon or faunal unit, the two species involved are not relevant to any generic or tribal revisions currently in progress and, being large and conspicuous elements in the Bahian fauna, deserve to be entered in the mainstream of ongoing knowledge.
Name: A neologism composed of the Greek elements plektron (a spur) + gonos (denoting the male reproductive appendage) + -desmus (a combining suffix widely employed throughout the order, from the original Polydesmus).Masculine.
Diagnosis: Body size large, length to near 70 mm.Among the known genera with enlarged gonopod aperture and prominent sclerotized median gonosternal sclerite, this new genus is characterized by the elongated paramedian processes of the 4 th segment in males, by small paramedian sternal lobes on segments 13-17 in males, by the greatly extended lateral prolongation of the gonopod coxa, and especially by the unusually long and etiolated elements of the telopodite.The efferent groove, visible for its entire length in mesal aspect, terminates on a long, slender subterminal solenomere.
Species: Only the type species is known.

Distribution:
The genus is known only from the type locality of the single included species, in the interior of the state of Bahia.

Comment:
The large black and yellow milliped named Leptodesmus gounelli by Brölemann in 1903 from a single male collected in the "Sertão" of Bahia, has apparently not been subsequently documented nor represented in museum collections normally holding these arthropods.The species was described in great detail and amply illustrated, with sufficient information to preclude its accommodation in Leptodesmus as currently defined, nonetheless it has remained an enigmatic, unplaced waif in the Brazilian fauna.Study of the holotype has disclosed additional structures not specified by Brölemann that confirm separate generic status for this striking species.
The unusually large gonopod aperture and sclerotized, bilobed, median sternal element suggest the form characteristic of the genera Eucampesmella Schubart, 1955, Leiodesmus Silvestri, 1987, and Euthydesmus Silvestri,1902, and it is perhaps to this last genus that we may look for a near relative despite the disparity in their ranges (E.acicarina Silvestri occurs in Mato Grosso do Sul).Structure of the undescribed female genitalia in all these chelodesmids may be decisive in developing a classification.
Material: The holotype has been examined.
Diagnosis: With the characters of the genus, further specific characters may be distinguished in the configuration of the gonopods when additional species are discovered.
Description (abstracted from original text): Body large, length 68 mm, width of 3 rd tergum, 10.8 mm, of 9 th tergum, 10.8 mm (prozonal diameter 6.8 mm) sides of body parallel, abruptly narrowed posteriad.Very dark reddish brown, almost black, with the peritreme and adjacent surface of the paranotum yellow.
Head somewhat shiny, divided by a well-defined suture extending between the antennae, and bearing up to their level a weak subtriangular depression.Antennae very long (12 mm) and slender, exceeding the posterior border of the 3 rd paranotum, not reflexed distally, antennomeres long and slender.
Collum much wider than the head, almost as broad as the following tergum, anterior border weakly arcuate medially, lateral ends narrowed to acute angle.Surface of metaterga dull, without transverse sulcus or seriate tubercles.Paranota well developed, placed at midheight of segments, a little declivous, continuing convexity of metaterga.Anterior corners broadly rounded, posterior obtusely rounded on anterior segments, becoming right-angled at midbody and increasingly acutely produced in going posteriad.Ozopores located in the posterior third of marginal peritremata, which form the posterior paranotal corner on all segments, and virtually the entire paranotum on segment 19 (Fig. 1).
Sterna broad, slightly elevated, with two paramedian projections between the posterior legpair of each postgonopodal segment (Fig. 2), anterior surface sparsely setose.Legs long and slender, the tibiae without apical subtarsal pads; pregonopodal legs without modifications.Sternum of segment 4 with two contiguous long processes (Fig. 3), sternum of segment 6 deeply concave for accommodation of the gonopodal apices.Gonopod aperture (Fig. 4) large, transversely oval, extending nearly to anterior edge of segment 7, and caudad between the 8 th pair of legs, posterior edge of aperture extended shelf-like into the cavity, this surface with several ridges in front of each coxa.
Gonopods notably large, coxae extended outside aperture rims, a large heavily sclerotized mesosternum; coxosternal apodeme elements nearly straight, elongated, apically a little enlarged.Coxa strongly prolonged on the lateral side (Fig. 7); a dorsal field of setae; no paracannular setae.Base of telopodite (prefemur) continuing main coxal axis, thence curved anteriad into a long very slender acropodite region, with small triangular apical lobe; efferent duct visible for its entire length in mesal aspect, carried by a slender acuminate solenomere.Acropodite region paralleled by a long slender prefemoral process, slightly broadened distally, with serrate edges.Neither acropodite nor prefemoral process with cingulum.
Comments: When visited by Gounelle in 1889, Santo Antonio da Barra was the name used for the city now called Condeúba in southwestern Bahia (14.53.35S, 41.59W).
Diagnosis: Distinguished from all known chelodesmid genera by the following combination of characters: size large (L to 70 mm), paranota well-developed, stricture costulate, prefemoral knobs and tibial pads absent, femora of legs 4 th -6 th pairs somewhat more incrassate than the others, those of 2 nd and 3 rd pairs with small but prominent ventrobasal lobe; anterior sternal processes of 5 th segment originating at coxal condyles long, acuminate, directed mesad with the apices in contact.
No sclerotized gonosternal sclerite present; coxa large and robust, with elongated coxosternal apodeme, dorsal coxal apophysis enlarged, with a field of setae on its lateral side, no paracannular setae present.Telopodite slightly smaller than coxa, lacking torsion, efferent groove conducted on a small laminate solenomere terminating the acropodite; prefemoral process large, calyciform, enveloping the acropodite.Neither element of telopodite with cingulum.
Species: Only the type species is known.
Comment: Like the foregoing species, the following has apparently never been recollected (or recorded) in over 100 years, and apparently mentioned only once, in 1938.In his 1903 paper, Brölemann sorted the various new species of Leptodesmus into several species groups, placing carminatus in the "Groupe du Leptodesmus plataleus" which corresponded to the taxon currently recognized as Chondrodesmus.Attems (1938) formally made the new combination Chondrodesmus carminatus although with considerable reservation, writing "Die Stellung dieser Art in der Gattung Chondrodesmus ist sehr zweifelhaft, die Gonopoden, die bei den anderen Arten sehr einheitlich sind, weichen bei dieser Art stark vom Typus ab, jedoch ist es schwer, sie zwanglos in einer Gattung unterzubringen."Lacking personal experience with the situation, Schubart accepted this assignation and did not include carminatus in his 1946 list of Brazilian species of Leptodesmus.Although Brölemann's perception was reasonable for its time, our better knowledge of chelodesmids associates Chondrodesmus and some closely related taxa in a discrete tribe Chondrodesmini endemic to the northern Andes and Middle America (Hoffman, 1978).The large gonosternum in Baianassa alone is sufficient reason to exclude it from that tribe.
Material examined: The holotype.
Diagnosis: With the characters of the genus, further specific characters may be identified in gonopod structure when additional species are discovered.
Description (partly from Brölemann): Length of holotype 63 mm., width of 9 th segment, 10.4 mm.Body robust, the anteriormost segment slightly the widest, parallel-sided except for the last three segments.Dorsum uniformly deep carmine, with a spot on each paranotum, a median spot on the caudal edge of the metaterga, antennae and legs yellow; ventral surfaces slightly paler red.Metaterga dorsally distinctly and densely coriaceous, from the 19 th segment with a vaguely defined sulcus, no transverse series of tubercles.Stricture finely costulate.Paranota large, set high on sides, mostly subquadrate, anterior corners broadly rounded; ozopores located on side of peritremata, which persist only as far as pore, not continued to posterior corner (Fig. 8-10).Sterna broad, flat, not as wide as length of femora, without subcoxal spines.Legs robust, 9.5 mm at midbody, tibiae without apical ventral pads; ventral surfaces with dense setation.Femora of 2 nd -4 th pairs of legs incrassate, with small ventral basal lobe (?adenostyle) (Fig. 11).Sternum of segment 5 with two paramdian pairs of slender, acuminate, mesially-directed processes (Fig. 12).
Gonopods (Figs. 13-15) relatively short and compact, without mesosternal sclerite; coxosternal apodeme slender and nearly straight in the coxal axis.Coxae not prolonged on the lateral side, but with a large, acute apophysis on the dorsal; a small field of setae on the dorsolateral surface; no paracannular setae.Telopodite set against coxa at nearly a right-angle; acropodite continues direction of prefemur.Telopodite dominated by the large, shield-like prefemoral process which encloses the short, simple acropodite.Efferent duct carried by the acropodite termination.No cingulum present on either component of the telopodite.
Comments: Although a number of tribal groups have been proposed in the Brazilian chelodesmid fauna in recent decades, none share the combination of characters that would accomodate Baianassa, which occupies a somewhat disjunct position.A disposition of this genus is probably contingent upon a much better knowledge of the (probably numerous) native chelodesmids of Bahia and adjacent states to the north.
The location of Santo Antonio da Barra is specified in the account of the preceding species.resumo Duas espécies de milípedes quelodesmídeos descritas por Brölemann (1903)