﻿A review of the cavernicolous Trichopolydesmidae (Diplopoda, Polydesmida) from the Carpathian-Balkan arch and the Rhodope Mountains, with descriptions of two new genera and three new species

﻿Abstract All cavernicolous species of the millipede family Trichopolydesmidae from the Carpathian-Balkan arch and the Rhodope Mountains have been reviewed. At present the family has been shown to comprise five or six genera with eight or nine species. Two new genera have been described, viz., Balkanodesminusgen. nov., with two new species: B.dentatoidessp. nov. and B.serbicussp. nov., from Bulgaria and Serbia, respectively, and the monospecific Rhodopodesmusgen. nov., with R.niveussp. nov., from Bulgaria. Two new combinations and one new status have been proposed: Balkanodesminusbulgaricus (Strasser, 1962) comb. nov. ex Bacillidesmusbulgaricus Strasser, 1962 and Balkanodesminusdentatus (Strasser, 1966a) comb. nov., stat. nov. ex Bacillidesmusbulgaricusdentatus Strasser, 1966a. All genera and species are diagnosed with the inclusion of the most relevant remarks for each of them. Old museum types are checked for Bacillidesmusfiliformis (Latzel, 1884) with lectotype designation, as well as for Trichopolydesmuseremitis Verhoeff, 1898. An identification key to all six genera and a distribution map for the eight species are provided, as well as brief remarks and general considerations on the family Trichopolydesmidae.


Introduction
The type species of the family Trichopolydesmidae, Trichopolydesmus eremitis Verhoeff, 1898 was described based on a single male collected in a cave near Băile Herculane in Romania. Given the limited general knowledge on the millipedes of that time, Verhoeff (1898) stated that the genus Trichopolydesmus Verhoeff, 1898 could in some respects be related to the genus Strongylosoma Brandt, 1833 (today in Paradoxosomatidae). At the same time, based on Latzel's (1884) specimens of the species Brachydesmus filiformis Latzel, 1884, Attems (1898) erected a new genus, Bacillidesmus Attems, 1898, which is today considered to be closely related to Trichopolydesmus. For these two genera, Verhoeff (1910) created two monospecific subfamilies within the family Polydesmidae, viz., Trichopolydesminae and Bacillidesminae. Brölemann (1916), to a certain extent, accepted Verhoeff's (1910) higher taxonomic ranking of the aforementioned taxon, but considered it as the tribe Trichopolydesmini, to which he assigned several other European and North African genera (mostly from the Mediterranean region). Later on, Attems (1926Attems ( , 1940 considered Trichopolydesmus and Bacillidesmus as members of the family Vanhoeffeniidae, an opinion with which Vehoeff (1941b) largely disagreed, considering Vanhoeffeniidae unacceptably heterogeneous. In that same paper he (Verhoeff 1941b) put the genus Trichopolydesmus, together with some South American taxa, in its own family, Trichopolydesmidae, not taking into consideration Brölemann's (1916) earlier classification of the tribe Trichopolydesmini. In the same work, Verhoeff (1941b) erected the monospecific family Bacillidesmidae for the genus Bacillidesmus. As for the family Vanhoeffeniidae, Jeekel (1956) argued that its type genus Vanhoeffenia Attems, 1908(see Attems 1908 is rather a member of the family Sphaerotrichopodidae, thus suppressing the family Vanhoeffeniidae. This act was apparently missed by some authors (e.g., Ceuca 1958 andSchubart 1960) who continued using the name Vanhoeffeniidae. Some years later, Jeekel (1965) synonymized Sphaerotrichopodidae and Vanhoeffeniidae under Dalodesmidae.
In the second half of the 20 th century, the status and the composition of Trichopolydesmidae remained debatable. Ribaut (1955) followed Brölemann's (1916) vision and included Galliocookia Ribaut, 1955 in the tribe Trichopolydesmini. Tabacaru (1975Tabacaru ( , 1980 treated the family Trichopolydesmidae in Verhoeff's (1941b) sense, with some South American taxa, but focused only on European taxa, and besides Trichopolydesmus, he added some other taxa, including Bacillidesmus. Hoffman (1980) restricted the family to only a few European genera. This concept was more or less followed by Mauriès (1984) who put in the family several European genera sensu Tabacaru (1975Tabacaru ( , 1980 and Hoffman (1980), one North African genus sensu Brölemann (1916), as well as several other European genera. Thus, considering Trichopolydesmidae to comprise taxa with chiefly Mediterranean distributions. Golovatch (2011) followed Mauriès' (1984) classification and additionally assigned to it the genus Caucasodesmus Golovatch, 1985 from the Caucasus and the Crimean Peninsula.
As far as the higher classification is concerned, Hoffman (1980) recognized the superfamily Trichopolydesmoidea within the suborder Polydesmidea. According to the same author, this superfamily includes all taxa that once belonged to the family Vanhoeffeniidae. He (Hoffman 1980) classified them into four families, viz., Trichopolydesmidae, Macrosternodesmidae, Nearctodesmidae and Fuhrmannodesmidae. In addition to these four families, Golovatch (2011) added the small Mediterranean family Mastigonodesmidae, simultaneously sharing Hofmann's (1980) view that the Fuhrmannodesmidae is a very heterogeneous family and that its members need to be divided into several natural groups. Two years later, Golovatch et al. (2013) further included in the group the family Opisotretidae, which had earlier been classified in the superfamily Polydesmoidea (sensu Hoffman 1980) or in its own superfamily Opisotretoidea (sensu Simonsen 1990). Interestingly, in the same year, Golovatch (2013) synonymized the families Mastigonodesmidae, Macrosternodesmidae, Nearctodesmidae, and Fuhrmannodesmidae with the family Trichopolydesmidae, leaving the Trichopolydesmoidea with only two families, viz., Trichopolydesmidae and Opisotretidae. In this way, Trichopolydesmidae became a large and obviously very heterogeneous group of millipedes. This view of the family Trichopolydesmidae was not well accepted by other authors, primarily due to the lack of a good diagnosis of this group (Antić et al. 2014;Tabacaru and Giurginca 2016). Tabacaru and Giurginca (2016) largely disagreed with such a classification of Trichopolydesmidae and restricted it to the European taxa only (12 genera), with the family's distribution spanning from the Iberian Peninsula, through the Alps, the Balkans, the Aegean region, the Crimean Peninsula all the way to the North Caucasus. A disagreement with Golovatch's (2013) classification was also expressed by Shear and Reddell (2017). These authors excluded the families Macrosternodesmidae and Nearctodesmidae from Trichopolydesmidae, leaving Macrosternodesmidae as a separate family with two subfamilies, Macrosternodesminae and Nearctodesminae, simultaneously synonymizing the superfamily Trichopolydesmoidea under Polydesmoidea. Finally, Golovatch et al. (2018Golovatch et al. ( , 2022, obviously accepted this act by Shear and Reddell (2017), but still treated Trichopolydesmidae in a broader sense, including Fuhrmannodesmidae and Mastigonodesmidae therein, with > 220 species in approximately 100 genera.
In the present paper, we review the cavernicolous members of the millipede family Trichopolydesmidae in the Carpathian-Balkan arch and the Rhodope Mountains (stretched between Bulgaria and Greece) and demonstrate that its fauna contains five or six genera with eight or nine species, including two genera and three species described here as new.

Material and methods
Preservation, dissecting, imaging, map Specimens preserved in 70% ethanol were examined with a Nikon SMZ 745T and a Zeiss Stemi 2000-C binocular stereo microscopes (IZB), a Nikon SMZ25 stereo microscope (NHMW), or a Carl Zeiss Discovery V8 stereo microscope (Institute of Biodiversity and Ecosystem Research). The gonopods and legs were dissected and mounted in glycerin for temporary microscope preparations and observed with a Carl Zeiss Axioscope 40 microscope (IZB). The gonopod and legs of Bacillidesmus filiformis type specimens, as well as habitus and gonopod of Trichopolydesmus eremitis holotype were photographed with a DS-Ri-2 camera mounted on a Nikon Eclipse Ni microscope using NIS-Elements Microscope Imaging Software with an Extended Depth of Focus (EDF) patch (NHMW). Photograph of T. eremitis male deposited in VMNH were taken with a Canon 9D camera with a 65 mm Canon MP-E macro lens (Canon, Tokyo, Japan) mounted on a Stackshot vertical rail system (Cognisys, Michigan, USA) and focus stacked in Helicon Focus Pro 7 (HeliconSoft, Kharkiv, Ukraine) (VMNH). Drawings of gonopods were executed using a computer monitor and pictures made with a Canon PowerShot A80 digital camera connected to an Axioscope 40 microscope (IZB) or with a DS-Ri-2 camera mounted on a Nikon Eclipse Ni microscope (NHMW). Pictures of specimens were taken using a Nikon DS-Ri-2 camera mounted on a Nikon SMZ25 stereo microscope using NIS-Elements Microscope Imaging Software with an Extended Depth of Focus (EDF) patch (NHMW). For Scanning electron microscopy (SEM) the specimens were: (1) cleaned in an ultrasonic bath (50-60 Hz) for 5 to 10 seconds (maximum), (2) dehydrated in an ascending alcohol series (70%, 80%, 90%, 96% EtOH, 2 × 10-15 min each) and acetone; (3) air dried. Specimens were mounted on aluminum stubs equipped with a sticky aluminum tape, coated with platinum (Leica EM SCD500) and studied with a JEOL JSM 6610-LV at an accelerating voltage of 15 kV or with a JEOL JSM-6460-LV (NHMW). Pictures of live animals were taken with an Olympus Stylus Tough TG-6 ( Fig. 2A), Canon PowerShot SX530 HS (Fig. 10A) and a Canon EOS 700D (Fig. 14A) digital camera.
The distribution map was created using Google Earth Pro (ver. 7.3.3.7786) and Adobe Photoshop CS6. The final images were processed with Adobe Photoshop CS6.

Gonopod terminology
The description of the basic parts of the gonopods of the new taxa followed Golovatch and VandenSpiegel (2015) with some modifications. The two basic parts of the gonopod are the coxa (cx) with a mesal cannula (ca), and the telopodite. The telopodite is composed of prefemorite (pf ) and acropodite (a). The prefemorite is transverse to the main axis of the animal's body, setose, and makes a nearly right angle with the acropodite. The acropodite is longitudinally divided into two branches, the mesal, solenomeral branch (sb), and the lateral solenophore (sph). Mesally on the prefemorite there is a seminal fossa (sf ), from which the seminal groove (sg) starts and runs along the mesal side of the acropodite all the way to the bifurcation point, then passes onto the solenomeral branch and ends with a small opening on the solenomere (s). Detailed and minute structures of the gonopods are explained directly in the figure captions and/or in the text. For more details on the terminology of the Polydesmoidea gonopods, see Shear and Marek (2021).  1A).
Distribution. Unknown. Remarks. In the original description, Latzel (1884) stated that he analyzed one pair (1 ♂, 1 ♀) that he had collected personally in "südöstlichen Ungarn" (= southeastern part of the Kingdom of Hungary). Later, Strasser (1962) assumed that the species came from "present-day Yugoslavia north of the Danube". This refers to today's Vojvodina, northern Serbia. However, the southeastern part of the Kingdom of Hungary included both Banat Mountains and Southern Carpathians (= Transylvanian Alps) in present-day Romania. Bearing in mind that this area is already inhabited by three trichopolydesmid genera, it seems more plausible that Bacillidesmus filiformis could have originated from present-day Romania, rather than northern Serbia which is characterized mainly by agricultural fields. It also remains unknown if this species is cavernicolous or epigean.
This taxon was originally described as Brachydesmus filiformis Latzel, 1884. Attems (1898) analyzed both Latzel's specimens of filiformis, and based on numerous differences with the genus Brachydesmus Heller, 1858, he correctly established a new genus, Bacillidesmus. At the same time, Attems (1898) gave the first gonopod drawing of this taxon (Fig. 17A). Later, in his famous "Polydesmoidea III", Attems (1940) provided a new drawing of the filiformis gonopod (Fig. 17B), which is slightly different from his 1898 drawing. After studying Attems' microslide with only one gonopod in poor condition (Figs 1G, 17C) we can confirm that it coincides a bit more with his schematic drawing from 1940. Unfortunately, the second gonopod, as well as ring 7 and both antennae of the lectotype, are most likely lost. It remains unclear whether Attems could have used the now-lost gonopod for the first drawing, or in both cases he used this one, which is still present today, but over time there have been partial changes in its position on the microslide or a partial deformation. Given that Attems (1898) also made a drawing of the antenna, which is missing today, it is very possible that there was another microslide with the second gonopod and antenna/antennae, which we failed to find. However, based on Attems' (1898Attems' ( , 1940 drawings and the newly examined type material of the gonopod, some conclusions could be drawn here. The genus Bacillidesmus had remained monospecific until Strasser (1962) provisionally included therein a new taxon from Bulgaria, based on a single female. Just a few years later, and this time with males in the hands, Strasser (1966a) confirmed that two more taxa belonged to the genus Bacillidesmus, viz., B. bulgaricus bulgaricus Strasser, 1962 andB. bulgaricus dentatus Strasser, 1966a. However, after a detailed examination of the type material of Bacillidesmus filiformis, as well as material of B. bulgaricus bulgaricus and B. bulgaricus dentatus, and two related new species from Serbia and Bulgaria, we believe that Bacillidesmus should include only filiformis, while the remaining aforementioned taxa should be assigned to a new genus, Balkanodesminus gen. nov., which we describe below. The new genus differs significantly from Bacillidesmus both in somatic and gonopodal characters. The most striking difference in the gonopod structure is that in Bacillidesmus filiformis the solenomeral branch is simple, without a distal solenomeral process, while in bulgaricus bulgaricus, bulgaricus dentatus and the two new species it is transversely bifid. In addition, these two genera differ significantly in several somatic traits: Bacillidesmus has regular rows of metatergal setae, mainly four, whereas Balkanodesminus gen. nov. shows 4-8 irregular rows; sensilla basiconica on antennomere 6: completely enclosed inside the pit in Bacillidesmus, vs. partially exposed outside the pit in Balkanodesminus gen. nov.; setae on paraprocts: 2+2 long setae in Bacillidesmus, vs. 2+2 long and ca. 10+10 shorter ones in Balkanodesminus gen. nov.; setae on hypoproct: 1+1 long distal setae in Bacillidesmus, vs. densely setose, including two long distal setae in Balkanodesminus gen. nov.; femora of all male legs swollen in Bacillidesmus, vs. only femora of legs 1-3 swollen in Balkanodesminus gen. nov.; anterior male legs in Bacillidesmus with ventral denticles, vs. denticles absent in Balkanodesminus gen. nov. These diferences are sound enough to propose a new genus for the taxa described by Strasser (B. bulgaricus bulgaricus, B. bulgaricus dentatus) and the two newly described species. Moreover, Bacillidesmus filiformis seems to show more affinity to some of the Carpathian genera (which is another proof that this genus could be from the Carpathians, see under Banatodesmus and Trichopolydesmus), while Balkanodesminus gen. nov., from the Balkan Mountains, shares many similarities with Rhodopodesmus gen. nov. (see below). Tabacaru, 1980 Type species. Trichopolydesmus (Banatodesmus) jeanneli Tabacaru, 1980, by monotypy. Diagnosis. Different from other European Trichopolydesmidae by the presence of an enlarged, oval, paddle-like solenomere (s in Fig. 4), with an additional, small, clawlike, distal solenomeral process (dsp in Fig. 4).

Genus Banatodesmus
In addition, the diagnosis can be amended with the following combination of characters: medium-sized species (7-7.5 mm), 20 body rings (including telson), rings with 4-6 irregular rows of long trichoid metatergal setae, sensilla basiconica completely enclosed inside the pit of antennomere 6, hypoproct with only two long distal setae, paraprocts with only 2+2 long setae, gonopod acropodite divided into two branches, solenophore (sph in Fig. 4) with three processes, of which the longest is S-shaped (broken off in the SEM image).     Distribution. This species has been described and is still known only from two caves in the Banat Mountains in Romania, Peştera Haiducească de la Moldova Nouă and Peştera de la Lacul Dracului caves (Fig. 18).

Banatodesmus jeanneli (Tabacaru, 1980)
Remarks. Originally, Banatodesmus was described as a subgenus of Trichopolydesmus Verhoeff, 1898(Tabacaru 1980. Later, Mauriès (1984) reasonably considered it as a separate genus, this being generally accepted today. Recently, in his book on Romanian millipedes, Giurginca (2021) referred to it as "Trichopolydesmus (Banatodesmus) jeanneli". This was apparently a mistake, since in the rest of the text Banatodesmus was clearly treated as a genus.
The sample examined here is the first record of this taxon since its original description. Two males and one female were discovered at one of the two type localities, Peştera Haiducească de la Moldova Nouă Cave. It is interesting that all three specimens were collected not far from the entrance to the cave, within one square meter, near a small stream that flows through the cave. The female was found under a piece of rotten wood, while both males were taken from under two deeply embedded stones.
Although Tabacaru (1980) provided an excellent description and very fine drawings ( Fig. 17D) of this taxon, the recently found specimens gave us the opportunity to document this taxon with photographs and SEM images of the habitus and gonopods (Figs 2-4).
As mentioned above, Bacillidesmus filiformis seems to show some habitual and gonopodal similarities with Banatodesmus. Both taxa share sensilla basiconica of antennomere 6 completely enclosed in the pit, paraprocts with only two long setae each, and hypoproct with only two long distal setae. In addition, the solenomeral branch and the solenophore are oriented mostly antero-posteriorly rather than meso-laterally to each other.

Diagnosis.
Cannot be compared to N. endogeus since its description was based on females only (see under Remarks).
Besides the hook-shaped posterolateral cones on the metaterga, this species differs from other European Trichopolydesmidae by the simplified gonopods with the acropodite divided in its distal third into two branches, a slender and claw-like solenophore and a wide and flattened, sublamelliform solenomere, both branches being parallel and oriented completely meso-laterally to each other (Fig. 17E, F).
In addition, the diagnosis can be amended with the following combination of characters: small species (3.4 mm), 19 body rings (including telson), sensilla basiconica on antennomere 6 partially exposed outside the pit, hypoproct with more than two long distal setae, paraprocts with more than 2+2 long setae, metaterga with 4-7 irregular rows of trichoid setae.
Remarks. Tabacaru (1975) stated that he had collected a male and a female, but that the female was lost during a breeding experiment. The excellent description and drawings ( Fig. 17E, F) he gave were based on only one male, which, if it still exists, should be treated as the holotype by monotypy.
The type species of this genus, N. endogeus, was described based on nine females found in the soil near the Biology Department at the University of Cluj in Romania (Ceuca 1974). Akkari and Enghoff (2011) cited this species from deep soil in an orchard in Moldova. Before that, Golovatch and Kime (2009) stated that this species is very common and abundant in Moldova's apple orchards, but probably accidentally under the name N. florentzae, instead of N. endogeus.
Diagnosis. Differs from other European Trichopolydesmidae by the gonopod acropodite divided into three branches, where solenomere is thin, long and acuminate, and devoid of additional process.
In addition, the diagnosis can be amended with the following combination of characters: medium-sized species (8.5 mm), 20 body rings (including telson), sensilla basiconica on antennomere 6 partially exposed outside the pit, paraprocts and hypoproct densely setose (Fig. 5F, G), metaterga with 4-6 irregular rows of long trichoid setae, podomeres of anterior legs in males with denticles on their ventral side, tarsi with rare sphaerotrichomes (Fig. 5H, I). Additional material. 1 ♂ (VMNH110683), body in two pieces in alcohol (Fig. 5C), ring 7 and gonopods missing. For more details see below.
Remarks. Verhoeff (1898) described this taxon from a single male he collected in the Hoţilor Cave in Băile Herculane. As he himself stated, several subsequent attempts to collect additional specimens in this cave were unsuccessful. Tabacaru (1980) stated that numerous searches in this cave failed too. One of us (DA) visited this cave in 2014 but also failed to find this species. In 2021, a small group of myriapodologists, including two of us (DA and BV) were not successful either. From Hoţilor Cave, only the male type specimen originally described by Verhoeff (1898) is known.
Sixty years after its original description, Ceuca (1958) examined more than 20 specimens of T. eremitis from three other caves and gave new and more detailed drawings of the gonopods (Fig. 17G, H), as well as some notes on female habitus. Hoffman (1980) wrote that he had received a male from Traian Ceuca, whose photograph is included in this paper (Fig. 5C). Unfortunately, colleague Jackson Means informed us that there is no original label with this individual, but that on the jar, marked with MIR02733, it is written: "Trichopolydesmidae: Trichopolydesmus eremitus Verhoeff TOPOTYPES !! Hungary". This was probably an accidental mistake during the subsequent labeling. The male sent by Ceuca to Hoffman comes from one of the three caves in Romania listed in Ceuca's (1958) paper. Considering the number of collected males from those three caves, we can only guess that this male comes from the Cloşani cave. Similarly to Bacillidesmus filiformis, this species also has ventral denticles on podomeres of male anterior legs (Fig. 5H, I). However, some other habitual characteristics are similar to Napocodesmus, Balkanodesminus gen. nov. and Rhodopodesmus gen. nov., viz., sensilla basiconica on antennomere 6 partially exposed outside the pit, while hypoproct and paraprocts are with more than two long setae (Fig. 5F, G). Legs and antennomeres (as well as antennae in general) in this species are somewhat longer (slender) than in other representatives from the Carpathian-Balkan arch and the Rhodope Mountains, thus it seems to be the most strongly adapted to cave life among them. Diagnosis. Differs from all European Trichopolydesmidae by the presence of a characteristic acropodite of the gonopods divided into two parallel and mostly meso-laterally oriented branches, where solenomeral branch is transversely bipartite, consisting of slender solenomere and well-developed distal solenomeral process. The most similar genus is Rhodopodesmus gen. nov., but it differs from Balkanodesminus gen. nov. and all other European Trichopolydesmidae by the presence of trifid solenomeral branch (for more details see under Rhodopodesmus gen. nov.).
In addition, the diagnosis can be amended with the following combination of characters: small size (3.7-5.2 mm), 19 body rings (including telson), sensilla basiconica on antennomere 6 partially exposed outside the pit, hypoproct with more than two long distal setae, paraprocts with more than 2+2 long setae, metaterga with 4-8 irregular rows of trichoid setae.
Name. The new genus is named after the Balkan Mountains, its type locality, in combination with the suffix -desminus, as a diminutive of -desmus, the common suffix in Polydesmida, referring to the small size of its species, in contrast to confamiliar Dinaric Balkanodesmus Antić & Reip, in Antić et al. 2014, the largest Balkan trichopolydesmid. The name is a masculine noun.
Remarks. Strasser (1962) described this species based on a poorly preserved female that he placed with uncertainty in the genus Bacillidesmus. He emphasized a very important difference in sensilla basiconica on 6 th antennomere being partially exposed in bulgaricus, while they are completely enclosed in their pit in filiformis.
Based on the distribution of the genus Balkanodesminus gen. nov., and the scattered distribution of B. bulgaricus gen. nov., comb. nov., we are not excluding the possibility that not all records of bulgaricus are in fact of that species. Illustrations of gonopods are known only from the two easternmost populations, from the Mladenovata peshtera Cave (Strasser 1966a) and Ponora Cave (present study).  (Strasser, 1962) gen. nov., comb. nov., ♂ from Ponora Cave, Bulgaria, left gonopod (NMNHS-10813) A, B mesal views C antero-distal view D distal view E lateral view F anterior view. Abbreviations: a acropodite, ca cannula, cx coxa, dp distal projection of solenophore, dsp distal solenomeral process, ll lamella of solenophore, pf prefemorite, s solenomere, sb solenomeral branch, sf seminal fossa, sg seminal groove, sph solenophore. Scale bars: 0.02 mm.
Remarks. Originally described as a subspecies, Bacillidesmus bulgaricus dentatus. Strasser (1966a) pointed out significant differences in the structure of the gonopod between bulgaricus and dentatus, as well as differences in body size. However, he did not notice the differences in the length and arrangement of metatergal setae between the two taxa. The descriptions of the two new species below, one of which is similar to bulgaricus in body size, habitus and gonopods, and the other one to dentatus, clearly indicate the presence of two groups of species within this genus.
Gonopods (Figs 9, 17M, N): Coxa (cx) large, semi-circular in ventral and lateral views, with differentiated gonocoel mesally; lateral part swollen, alveolate, with three long setae near mesal ridge. Cannula (ca) long, C-shaped. Telopodite relatively long compared to coxa, consisting of a transverse, setose prefemorite (pf ) and a somewhat C-shaped (in lateral and mesal views) acropodite (a) longitudinally divided in the distal half into two branches, solenomeral branch (sb) and solenophore (sph). Solenomeral branch positioned mesally, with a narrow "neck", then abruptly expands and transversely divides into two processes, solenomere (s) and distal solenomeral process (dsp). Extended part of solenomeral branch with spiculiform outgrowths. Solenomere (s) very long, slender, subdistally with a small bifurcation. Distal solenomeral process (dsp) extends in the same direction as solenomere and is half as long as solenomere; bifurcated=with small additional mesal tooth (t). Solenophore (sph) longer and more robust than solenomeral branch, characterized by a robust, lateral, ear-shaped lamella (ll) and a distal projection (dp). Lateral lamella (ll) begins at bifurcation of solenomeral branch and solenophore, surrounding laterally solenophore up to beginning of distal ending; lateral margins of lamella denticulated. Distal projection (dp) with strongly developed, basal lamellar lobe (bl), with mesal thickening (mt) and with relativelly short and acuminate process (ap). Seminal groove (sg) starts from seminal fossa (sf ) mesally on prefemorite, extends along mesal side of acropodite up to bifurcation of solenomeral branch and solenophore, then passes on lateral side of solenomeral branch, further on solenomere, ending distally.
Habitat. Saeva dupka Cave is a show cave which is now heavily impacted by electrification and continuous touristic flow. The cave has naturally formed 400 meters of corridors and halls. The samples from the cave were taken in 1997, under stones in clay, when the cave was temporarily closed for visitors due to the change of its governance during the democratic changes in Bulgaria. After more than 20 years of active exploration of the cave, new material needs to be collected to assess whether the species was influenced by the human activities. Saeva dupka Cave is inhabited by numerous and diverse invertebrate taxa, but the only troglobiont currently on record is the local endemic Bulgariella tranteevi Z. Karaman, 1958 (Coleoptera, Leiodidae) (Beron 2015).
Distribution. So far known only from two caves in Lovech District (Fig. 18).
Remarks. Based on material from Saeva dupka Cave, Stoev (2004) already noticed that there were certain differences in the structure of gonopods of that sample and Bacillidesmus dentatus, and he did not exclude the possibility that it belonged to a new taxon. However, he still treated this as Bacillidesmus bulgaricus dentatus. After reviewing the material that was available to him, as well as based on the newly studied material, we describe it above as a new species. Figure 9. Balkanodesminus dentatoides gen. nov. et sp. nov., right gonopods A-E paratype ♂ (NHMW MY10258) A mesal view B lateral view C meso-distal view D antero-distal view E tip of solenomere, distal view F, G ♂ from Sopotska peshtera Cave (NHMW MY10267), mesal and antero-disto-lateral views, respectively. Abbreviations: a acropodite, ap acuminate process of solenophore, bl basal lamellar lobe of solenophore, ca cannula, cx coxa, dp distal projection of solenophore, dsp distal solenomeral process, ll lamella of solenophore, mt mesal thickening of solenophore, pf prefemorite, s solenomere, sb solenomeral branch, sf seminal fossa, sg seminal groove, sph solenophore, t mesal tooth of distal solenomeral process. Scale bars: 0.02 mm (A-D, F, G), 0.005 mm (E).

Description. Number of body rings and measurements:
Body with 19 rings (including telson) in adults, moniliform (Fig. 10). Holotype male and paratype male 4.8 mm and 4.7 mm long, respectively; width of midbody pro-and metazonae 0.30 mm and 0.45 mm, respectively. Paratype females 5.0 mm and 5.2 mm long, width of midbody pro-and metazonae 0.35 mm and 0.50 mm, respectively.
Collum: Semi-circular, with one or two lateral incisions and ≈ 5 irregular rows of relatively long and trichoid setae.
Gonopods (Figs 13,17J): Coxa (cx) large, semi-circular in ventral and lateral views, with differentiated gonocoel mesally; lateral part swollen, alveolate, with three long setae near mesal ridge. Cannula (ca) long, C-shaped. Telopodite long compared to coxa,  consisting of a transverse, setose prefemorite (pf ) and a somewhat C-shaped (in lateral and mesal views) acropodite (a) longitudinally divided in its distal half into two branches, solenomeral branch (sb) and solenophore (sph). Solenomeral branch positioned mesally, with a narrow base, then abruptly expands and transversely divides into two processes, solenomere (s) and distal solenomeral process (dsp). Solenomere (s) long, slender, distally expanded (in lateral and mesal views), forming U-shaped rift with distal solenomeral process. Distal solenomeral process (dsp) extends in the same direction as solenomere, ¾ the length of solenomere; ending with a small expansion (in lateral and mesal views). Solenophore (sph) longer and more robust than solenomeral branch, characterized by a lateral, ear-shaped lamella (ll) and a distal projection (dp). Lateral lamella (ll) begins at bifurcation of solenomeral branch and solenophore, surrounding laterally solenophore up to beginning of distal projection; lateral margins of lamella smooth. Distal projection (dp) sigmoid (in lateral and mesal views), with well-developed, basal lamellar lobe (bl). Seminal groove (sg) starts from seminal fossa (sf ) mesally on prefemorite, extends along mesal side of acropodite up to bifurcation of solenomeral branch and solenophore, then passes on lateral side of solenomeral branch, further on solenomere, ending subdistally.
Habitat. With its 6131 m of explored channels, the Cerjanska Cave represents one of the longest and most significant fluviokarst underground systems in Serbia. This is a relatively simple speleological object, consisting of one main river channel in two levels with a length of 4903 m, as well as several side channels with a total length of 1228 m (Nešić 2016). Numerous arthropod taxa have been registered in the cave, from epigean, guanophiles, trogloxenes, and troglophiles to troglobionts (Pavićević et al. 2016). The troglobionts include the endemic Balkan harvestman Paranemastoma bureschi (Roewer, 1926), the millipede Dazbogosoma naissi Makarov & Ćurčić in Makarov et al. 2012, and the carabid beetle Duvalius rtanjensis provalijae Pavićević, Zatezalo & Popović, 2016, the latter two endemics of Cerjanska Cave.
Despite many years of speleological and biospeleological research in the Cerjanska Cave, the new taxon was not registered until the first Biospeleological Expedition of the Serbian Biospeleological Society, organized at the end of October 2017. All 11 specimens were found in a small area, in the initial part of the cave. One male, one female and seven juveniles were found on the left side of the river, on a small branch of a tree lying on the wet sand. Another male and female were found just on the opposite side of the river, on the wall, in copulation (Fig. 10A).
Distribution. So far, known only from its type locality, the Cerjanska Cave, Serbia (Fig. 18).
Remarks. This is the first representative of the family Trichopolydesmidae in Serbia.

Taxa from the Rhodope Mountains
Genus Rhodopodesmus gen. nov. http://zoobank.org/1D609274-0185-4A6E-85CF-D32654CBFEF9 Type species. Rhodopodesmus niveus gen. nov. et sp. nov., by monotypy. Diagnosis. Differs from all European Trichopolydesmidae by the presence of characteristic acropodite of the gonopods divided into two branches that are parallel and completely meso-laterally oriented to each other, with solenomeral branch transversely tripartite, where the proximal-most branch is the shortest, while solenomere and distal solenomeral process are longer and of the same length. The most similar genus is Balkanodesminus gen. nov., but it differs from Rhodopodesmus gen. nov., by the presence of bifid solenomeral branch (for more details on gonopod differences see below under Remarks).
In addition, the diagnosis can be amended with the following combination of characters: small size (4.3-5.4 mm), 19 body rings (including telson), sensilla basiconica on antennomere 6 partially exposed outside the pit, hypoproct with more than two long distal setae, paraprocts with more than 2+2 long setae, metaterga with 4-8 irregular rows of medium-sized trichoid setae.

Name.
The new genus is named after the Rhodope Mountains, its type locality, in combination with -desmus, the common suffix in Polydesmida. The name is a masculine noun. Diagnosis. As for the monospecific genus.

Rhodopodesmus niveus
Name. The specific name is a Latin adjective; niveus refers to the snow-white body color of the living specimens. Furthermore, the name of the type locality, cave Snezhanka, in Bulgarian means Snow White, the heroine from the fairy tale of the Brothers Grimm.
Gonopods (Figs 16,17K): Coxa (cx) large, semi-circular in ventral view, with deep gonocoel mesally; anterior third much lower than rest of coxa, shield-like, thus lateral, swollen and alveolate part rectangular in lateral view; with ≈ 15 setae. Cannula (ca) long, C-shaped. Telopodite long compared to coxa, consisting of a transverse, setose prefemorite (pf ) and more or less C-shaped (in lateral and mesal views) acropodite (a) longitudinally divided in distal half into two branches, solenomeral branch (sb) and solenophore (sph). Solenomeral branch positioned mesally, transversely divided into three processes, besides solenomere (s) and distal solenomeral process (dsp), there is an additional, proximal solenomeral process (psp), more or less spatulate and forming C-shaped rift with solenomere. Both solenomere (s) and distal solenomeral process (dsp) long, slender, of same length, forming acute angle at bifurcation. Solenophore (sph) longer than solenomeral branch, characterized by a lateral lamella (ll) and a distal projection (dp). Lateral lamella (ll) with triangular lobe. Distal projection (dp) long, thin and twisted. Seminal groove (sg) starts from seminal fossa (sf ) mesally on prefemorite, extends along mesal side of acropodite up to bifurcation of solenomeral branch and solenophore, then passes on lateral side of solenomeral branch, further proximally on solenomere, ending distally.
Habitat. Snezhanka Cave consists of a single gallery forming six distinct halls with total length of 348 m. The entrance is located at 865 m a.s.l. The cave is rich in diverse sinter formations and sinter ponds. It was established as a natural monument in 1961, and has served as show cave since 1968 (Petrov and Stoev 2007). Most of the cave's invertebrate fauna known at present includes either trogloxenes or troglophiles (Beron 2015), with the exception of the local endemic Paralovricia beroni Giachino, Guéorguiev & Vailati, 2011 (Coleoptera, Carabidae), which is considered a probable hypogean, although not typical troglobitic species (Giachino et al. 2011). Another myriapod known from this cave is Lithobius lakatnicensis Verhoeff, 1926. All five recently collected specimens of Rhodopodesmus niveus gen. nov. et sp. nov. by D.A. and B.V. were found in the middle part of the cave at two spots, and all were in rotten wood.
Distribution. So far, known only from its type locality, the Snezhanka Cave, Bulgaria (see also under Remarks) (Fig. 18).
Remarks. As mentioned above, it seems that the most similar genus to Rhodopodsemus gen. nov. is Balkanodesminus gen. nov., which makes sense due to their distributions. These two genera share not only similarities in certain habitus features but also in the gonopods. Both include small-bodied species with 19 rings in adults, with sensilla basiconica on antennomere 6 partially exposed outside the pit, hypoproct with more than two long  Abbreviations: a acropodite, ca cannula, cx coxa, dp distal projection of solenophore, dsp distal solenomeral process, ll lamella of solenophore, pf prefemorite, psp proximal solenomeral process, s solenomere, sb solenomeral branch, sf seminal fossa, sg seminal groove, sph solenophore. Scale bars: 0.05 mm. distal setae and paraprocts with more than 2+2 long setae. The conformation of the gonopods is very similar, where the acropodite is longitudinally divided into two branches, with the solenomeral branch transversely divided into long and relatively slender solenomere and well-developed distal process in both genera. Based on this, both genera differ from other European Trichopolydesmidae. However, in Rhodopodesmus gen. nov. the solenomeral branch is trifid, where in addition to solenomere and distal process, in the base of this branch there is another, proximal process, which is more or less spatulate. These two genera also differ in some details of the gonopod coxa. Rhodopodesmus gen. nov. has a very deep gonocoel, i.e., the anterior third of the coxa is much lower than the rest it, in the form of a shield, so that the rest of the coxa has a more or less rectangular shape laterally, while in Balkanodesminus gen. nov. it is semi-circular. Also, the coxa in Rhodopodesmus gen. nov. has circa 15 setae, while the same in species of Balkanodesminus gen. nov. bears only 3.
It is worth mentioning that specimens of Rhodopodesmus gen. nov. were found in two more caves in the Rhodopes, viz., one female in Dupkata (= Dupcheto) Cave near Rakitovo and one male and one female in Skoka Cave near Ribnovo. Unfortunately, the material from Skoka Cave (including one male) could not be relocated in NM-NHS for this study, and we still do not know whether it is R. niveus gen. nov. et sp. nov. or a new species. The female from Dupkata Cave probably belongs to R. niveus gen. nov. et sp. nov. considering its proximity to the type locality of this species. Both localities are mapped (Fig. 18, yellow squares), and already noted under Bacillidesmus sp. nov. by Vagalinski and Stoev (2011).  Fig. 17I, J, L-N) To distinguish easily all six genera and nine species see Fig. 17.

Discussion
The family Trichopolydesmidae, as accepted today (see Golovatch et al. 2018Golovatch et al. , 2022, includes ≈ 100 genera and > 220 species, which are mostly distributed in the Northern Hemisphere. Unfortunately, the family cannot be clearly defined and diagnosed, as it includes a wide range of taxa that differ significantly not only in appearance, but also in gonopod conformation. However, according to Tabacaru and Giurginca (2016), this family is composed of exclusively European genera: Trichopolydesmus (monospecific), Bacillidesmus (monospecific), Cottodesmus Verhoeff, 1936 (2 species), Galliocookia Ribaut, 1955 (4 species), Verhoeffodesmus Strasser, 1959 (monospecific), Occitanocookia Mauriès, 1980 (monospecific), Caucasodesmus (5 species nov., they all seem to form a natural group characterized by the following combination of characters: metatergal setae always trichoid, in most cases on small tubercles arranged almost always in more than four irregular transverse rows, antennomere 5 without distodorsal sensilla basiconica, antennomere 6 always with sensilla basiconica in a distodorsal sensory pit, completely or partially concealed inside, gonopod telopodite relatively long compared to gonopod coxa, basal part of prefemorite transverse to the body axis, acropodite uni-, bi-or triramous, always without seminal vesicle or pulvillus. Chiefly for the purpose of this discussion we will call this group "true" trichopolydesmids. The other three genera considered in Trichopolydesmidae sensu Tabacaru and Giurginca (2016), viz., Cottodesmus, Galliocookia, and Occitanocookia, also show some affinities with this group, but differ in a number of important characters. Both species of the genus Cottodesmus are characterized by bacilliform rather than trichoid setae on metaterga. Although Verhoeff (1936) described C. crissolensis Verhoeff, 1936 with trichoid setae, after examination of the female syntype, it becomes clear that the setae are bacilliform and arranged in four almost regular rows. Further, at least C. crissolensis is characterized by sensilla basiconica on both antennomeres 5 and 6, with no sensory pits in both cases. Similar to Cottodesmus, the genus Occitanocookia is characterized by sensilla basiconica on antennomeres 5 and 6, but with trichoid metatergal setae arranged in several irregular rows, as in the "true" trichopolydesmids. Furthermore, the latter genus shows gonopodal prefemorites that are set transverse to the body axis, and a somewhat curved acropodite, both characters observed in the "true" trichopolydesmids. The species Galliocookia gracilis Golovatch, 2011, found on Rhodes (very far from the remaining distribution area of the genus in France), possesses sensilla basiconica on antennomeres 5 and 6, while its other three congeners lack sensilla on antennomere 5, like in "true" trichopolydesmids. The generic assignment of the species described from Rhodes, Greece to Galliocookia is in our view questionable. In any case, the relatively small gonopodal coxa and prefemorite -which is almost coaxial with the acropodite -places the genus quite distant from the above-mentioned group. In addition to these 14 genera of (autochthonous?) European Trihopolydesmidae, the recently established genus Simplogonopus Vagalinski, Golovatch, Akkari & Stoev, 2019, known from the Balkan mainland and Aegean islands, is classified in Trichopolydesmidae sensu Golovatch (2013) and Golovatch et al. (2018) (Vagalinski et al. 2019). This genus clearly belongs to Afrotropical trichopolydesmids, which are significantly different from the "true" trichopolydesmids from Europe in the presence of exclusively bacilliform metatergal setae distributed mainly in three regular transverse rows, distodorsal sensilla basiconica on antennomeres 5 and 6, but antennomere 6 without distodorsal pit and with relatively small gonopod telopodites, almost completely concealed by very large coxae. The genus Simplogonopus and all Afrotropical trichopolydesmids appear to form one natural group (cf. Golovatch et al. 2019Golovatch et al. , 2022 whose representatives were once assigned to the family Fuhrmannodesmidae. Two more Mediterranean genera from North Africa are often attributed to the family Trichopolydesmidae as well, viz., Heterocookia Silvestri, 1898and Haplocookia Brölemann, 1915(Akkari and Mauriès 2018. However, these two genera differ from the "true" trichopolydesmids in the presence of three regular transverse rows of bacilliform metatergal setae, and in having both antennomeres 5 and 6 with a distodorsal group of sensilla basiconica, and in showing both gonocoxa and prefemorite rather small. These two latter taxa, as well as the above mentioned genus Galliocookia, have been attributed to the family Polydesmidae by Hoffman (1980). It is obvious that the current classification of Trichopoly-desmidae is very chaotic and cannot be a ground for any phylogenetic approaches. Some authors believe that the family should be reduced to the European genera only, others assign to it also the North African genera or consider it in a broader sense, including many taxa once classified in the family Fuhrmannodesmidae (Golovatch 2013;Golovatch et al. 2018Golovatch et al. , 2022. The composition and the relationships of the taxa of Trichopolydesmidae could be resolved only after applying combined morphological and molecular phylogenetic methods. Until then, and relying on morphological characters hitherto applied to the classification of the group only, we tend to believe that Trichopolydesmidae should be restricted to the European genera sensu Tabacaru and Giurginca (2016), with the addition of the genera Balkanodesminus gen. nov. and Rhodopodesmus gen. nov. described above.
The genera of what was previously considered as the family Fuhrmannodesmidae seem to form several natural groups (cf. Hoffman 1980;Golovatch 2011), while some other genera (Heterocookia and Haplocookia) might well be placed in Polydesmidae. Opinions on the classification of Trichopolydesmidae are highly subjective and, as emphasized earlier, only an integrative approach using molecular markers might clarify the picture in the future.
The Balkan Peninsula, including the southern Carpathians, is obviously a hotspot for the family Trichopolydesmidae, with as many as ten "true" trichopolydesmid genera known mostly from caves in the Balkans. All ten genera are characterized by four or more irregular rows of trichoid setae (except for Bacillidesmus with four regular rows), absence of sensilla basiconica on antennomere 5, presence of a distodorsal pit with sensilla basiconica on antennomere 6, as well as gonopods with a relatively transverse basal part of the prefemorite. The genus Caucasodesmus, known from caves in the north Caucasus and the Crimean Peninsula (see Golovatch 1985Golovatch , 2011VandenSpiegel 2015, 2017;Turbanov et al. 2018), also agrees with this combination of characters. The only exception is C. inexpectatus Golovatch, 1985, which has three rows of trichoid setae.
Two morphological clusters of Trichopolydesmidae could be recognized among the taxa inhabiting the Balkan Peninsula: the Dinaric and the Carpathian-Balkan-Rhodopean ones. All taxa described from the Dinarides are characterized by well-developed and denticulate pleurosternal carinae on rings 2-18 (see Antić et al. 2014), while taxa from the Carpathian-Balkanids and Rhodopes have only a few pleurosternal teeth on anterior rings (mainly on rings 2-4). Eight of ten Balkan genera are monospecific, including the genus Verhoeffodesmus, although Strasser (1959Strasser ( , 1966b described two species (see Antić et al. 2014). Again, the Balkan Peninsula proves to be a prominent hotspot of millipede diversity in Europe. This primarily concerns the cave fauna, with trichopolydesmids being no exception. Better equipment and more manpower in the recent years have contributed to the discovery of interesting taxa, also from this group, primarily in the Dinarides, whence Antić et al. (2014) described three new monospecific genera. However, from the description of these three genera to date, about ten new taxa have been found in caves of the Dinarides, and these monospecific genera will be supplemented in the future (DA pers. obs.). It is worth mentioning that the fauna of the type locality of B. serbicus gen. nov. et sp. nov. has been investigated for years, but specimens of this taxon have been found only recently. This leaves no doubt that more trichopolydesmids will be revealed and described from the Balkans in the future.