TWO NEW SPECIES OF BRACHYDESMUS HELLER, 1858 FROM THE BALKAN PENINSULA (DIPLOPODA: POLYDESMIDA: POLYDESMIDAE)

Two new polydesmid species are described, illustrated, and diagnosed: a troglobitic, Brachydesmus mulaomerovici n. sp., from Bosnia and Herzegovina and epigean Brachydesmus verrucosus n. sp. from Macedonia. The new taxa belong to inferusand stygivagus-groups of species, respectively. Relationships with congeners are briefly discussed. The distribution map and key are given for all currently known taxa belonging to these groups of species.


INTRODUCTION
Among the three southern European peninsulas -Iberian, Apennine and Balkan, that had a major role as refugial zones during the last glaciation in the Pleistocene (Hewitt, 1999), for both paleo-and neoendemic forms, the Balkan Peninsula shows the highest degree of species richness and endemism (Čurčić, 1998;Gaston and David, 1994;Savić, 2008).Its geographical position, between the Pannonian Basin in the north and Mediterranean region in the south, geomorphological and climatic events, as well as the historical development of the fauna on the Balkan Peninsula have made this area the center of speciation, diversification and adaptive radiation in many invertebrate groups (Ćurčić, 1998;Ćurčić et al., 2002;Savić, 2008).
Among the rich European millipede fauna, the genus Brachydesmus Heller, 1858, is one of the most numerous.According to Enghoff and Kime (2011), about 70 species of this genus inhabit Europe, of which nearly 80% are described from epigeic, endogeic and cave habitats on the Balkan Peninsula.Such species richness confirms the hypothesis that the Balkans (especially the former Yugoslavia) are a center of diversification of this genus.
After careful examination of abundant samples of diplopods from the Balkan Peninsula containing many interesting, rare and topotypic species, we determined that two of them are new to science.Description, illustration and diagnosis of these new taxa, as well as a brief discussion on congeners, and a distributional map are presented in this paper.
The terminology we have used for the description of polydesmid gonopods was proposed by Djursvoll et al. (2000), and Golovatch and Wytwer (2007).
The type specimens (holotype male, allotype female, two paratype males and eight paratype juveniles from Bosnia and Herzegovina and holotype male, allotype female and paratype female from Macedonia) are deposited in the collection of the Institute of Zoology, Faculty of Biology, University of Belgrade (Belgrade, Serbia).Etymology -After Dr. Jasminko Mulaomerović, the well-known Bosnian speleologist and naturalist, and "spiritus movens" of Bosnian speleology.

BRACHYDESMUS MULAOMEROVICI
Diagnosis -The new species clearly differs from B. inferus Latzel, 1884 andB. likanus Strasser, 1962, by the presence of well-developed paranota that are not curved upward, as well as by the specific structures of the gonopods.
Walking legs: elongated, without any modification.
Distribution -Probably endemic species of Bosnia and Herzegovina.Material examined -Holotype male from Skopska Crna Gora Mountain, near Saint Ilija Monastery, 600 m elevation, northern Macedonia; April 16, 2006.Allotype female and paratype female, same data as holotype.
Diagnosis -From B. stygivagus Verhoeff, 1899 (Fig. 16), new species clearly differs by many characteristics of the gonopods.Above all, there is a distinct difference in the general shape of the gonopods, as well as a difference in the structures of the prefemorite, femorite and exomere.
Collum: With semicircular anterior edge and gently concave posterior edge.One medial incision present on both lateral sides; with three transverse rows of setae; setal formula (holotype male): 8+8+8.
Distribution -Probably endemic species of Macedonia.

DISCUSSION
The genus Brachydesmus includes small-to mediumsized polydesmids, with poorly pigmented or depigmented body, living cryptic or underground life.The vast majority of species of this genus inhabit Europe, while a small number are native to Caucasus, Anatolia, Hyrcania and Levant (Golovatch and Wytwer, 2007); introduced to other parts of the world (Enghoff and Kime, 2011).
Within the genus Brachydesmus, numerous closely related taxa exist and 13 subgenera were included.After synonymization of all subgenera under the nominal genus Brachydesmus (Enghoff and Kime, 2011), the need for separation of the groups of species arose.Recently, Antić et al. (2013) recognized at least three groups of species: vermosanus-, ljubetensis-and jubatus-group.In this paper, we differentiated an additional two groups of species.
1.The inferus-group includes three species: Brachydesmus inferus Latzel, 1884 (for synonyms see Attems, 1940;Strasser, 1971;Mršić, 1988), B. likanus Strasser, 1962, andB. mulaomerovici n. sp. Strasser (1962) and Mršić (1988) pointed out the similarities between B. inferus and B. likanus.According to Strasser (1962), these similarities are reflected in some structures of the gonopods, especially the exomere, as well as in the shape of the paraterga, which is in both species with upward curved wings.Similarities in the gonopod struc-tures are reflected by the presence of an inner long and thin process and two external ones on the exomere, as well as the presence of an inner femoral lobe.Differences between these two species are: the presence of two caudal processes on the prefemorite in Caudally on the femorite, both species possess an embossment, above which is the pulvillus with two similar triangular teeth.In general, the shape and structure of the gonopods to the exomere are very similar between B. likanus and B. mulaomerovici n. sp.Differences between these two taxa are reflected in the shape and structure of the exomere.Both species possess a mesal process, but in the new taxa, this process is very long, thin, pointed and not extended at the base, while B. likanus possesses a shorter and very extended mesal process at the base, which looks more like a separated branch.In addition, the new species possess a long and apically bifurcated process which is absent in B. likanus.Furthermore, the new taxon differs from B. likanus and B. inferus in the presence of very well developed paranota without upward curved wings.We supposed that, according to Djursvoll et al. (2000), the new species possess some plesiomorphic features, such as a depigmented body, relatively long femorite and short prefemorite, an absence of any kind of teeth, processes or extensions on the prefemo-rite, absence of marked excavation on femorite, a relatively short and unipartite exomere as well as the absence of a solenomere.However, some apomorphic characters appear in the new species: blunt setae on the somites, an absence of acropodite as well as presence of well-developed processes on the exomere (Djursvoll et al., 2000).The depigmented body with elongated antennae and walking legs in the new species indicates its clear troglomorphism.
In B. stygivagus, the gonopods show some variability.This variability is reflected by the presence of long or short thorn with or without hairs on the border between the prefemorite and femorite; the presence of a bifurcated or simple acropodite; the presence or absence of a subapical process, as well as the presence of a divided or undivided lobular process.Regardless of which characteristics are concerned, the new species clearly differ from those previously mentioned in the general shape of the gonopods.Instead of long or short thorn on the border between the prefemorite and femorite, the new species possess two well-developed triangular processes, with a U-shaped rift between.In some forms of B. stygivagus, denticles are present on the oral side of the exomere, while the new species possess a warty dorsomesal side of the exomere.Also, the difference is reflected in the construction of the exomere, which is simple at the top and possesses only one apically bifurcated process in the new species, while the same structure in B. stygivagus is denticulated apically with, mainly, two processes: subapical and lobular.In the new species, many apomorphic characteristics are present.These are a pigmented body, excavation on the femorite, a relatively long exomere with strong bifurcated process (see Djursvoll et al., 2000), triangular processes between prefemorite and femorite as well as a warty dorsomesal side of the exomere.The absence of a solenomere, presence of a well-developed acropodite and trichoid setae on the somites can be considered as plesiomorphic according Djursvoll et al. (2000).It is of interest to note that the new species possess bilobed caudolateral corners of the paranota.This is characteristic only for B. langhofferi Verhoeff, 1929, B. granulosus Makarov et al., 2003 and for the genus Brembosoma Verhoeff, 1931 (Djursvoll et al., 2000;Makarov et al., 2003).The status of the former B. zawalanus Attems 1912, with three subspecies, which are synonymized under B. stygivagus, is questionable.There are some differences in gonopod structure, as well as differences in the general shape and size of the gonopods between these forms, possibly indicating their independent status (Fig. 16).This remains an open question for future research.
Representatives of the inferus-group inhabit caves and forests of the Dinaric Karst in Slovenia, Croatia, Bosnia and Herzegovina and Montenegro (Map 1) (Attems, 1940(Attems, , 1959;;Mršić, 1988).The most common species of this group is B. inferus, known from many cave and forest habitats in Slovenia and Croatia.According to Attems (1959), this species was recorded from one cave in Herzegovina (Bukovica Ponor at Gacko, northeastern Herzegovina) and one in Montenegro (Krivošije, Careve-Pećine in Elesov dô).B. likanus is known only from three sites in Lika, a geographic region in mountainous Croatia, while B. mulaomerovici n. sp. is known only from the type locality in the central part of Bosnia and Herzegovina.A more southern distribution shows representatives of the stygivagus-group of species (Map 1).B. stygivagus is known from numerous caves, mainly in the coastal parts of southern and central Croatia, southern Bosnia and Herzegovina and Montenegro (Attems 1940(Attems , 1959;;Mršić 1988;Makarov et al., 2004), while B. verrucosus n. sp. is known only from one site on the Skopska Crna Gora Mountain in northern Macedonia, and probably represents an endemic species of this mountain.
The discovery of two new species of the genus Brachydesmus from the Balkan Peninsula confirms the hypothesis mentioned at the beginning, that this part of southern Europe, especially the Dinaric Karst of former Yugoslavia, represents a center of diversification of this millipede genus.
B. inferus vs. absence of these structures in B. likanus; a triangular and prominent femoral lobe in B. inferus vs. smaller and not triangular femoral lobe of B. likanus; an inner process of the exomere without any denticles in B. inferus vs. an inner process with one or two denticles in B. likanus, and a basally curved-down inner tooth on the pulvillus of B. inferus vs. an inner pulvillus tooth not curved downwards in B. likanus.We have assigned B. mulaomerovici n. sp. a preliminary designation to this group of species based on the similarities in gonopod structures with B. likanus.These similarities are related primarily to the structure of prefemorite and femorite.In both species, the prefemorite is simple, without any of the teeth, processes or extensions present in B. inferus.In addition, the femorite is very similar between B. likanus and new species.