Morphology, taxonomy and distribution of Diphyonyx gen. n., a lineage of geophilid centipedes with unusually shaped claws (Chilopoda: Geophilidae)

According to the currently most followed systematic arrangement of the geophilomorph centipedes (Chilopoda Geophilomorpha), almost half of the known species in this group belongs to the single family Geophilidae (Minelli, 2006). With more than five hundred described species distributed throughout the world, geophilids represent a taxon only vaguely diagnosed and still in need of being more rigorously circumscribed within a phylogenetic framework. The internal taxonomic arrangement of the geophilids also appears unsatisfactory. Within the fauna of the Western Palaearctic, where geophilids are highly diverse and most students have concentrated their investigations, the arrangement of species in genera deserves extensive revision: some genera (e.g., Geophilus Leach, 1814 and Brachygeophilus Brölemann, 1909) are still used by authors under very broad concepts, that encompass diverse and apparently composite assemblages of species; conversely, other nominal genera (e.g., Bebekium Verhoeff, 1941, Folkmanovius Dobroruka, 1957 and Photophilus Folkmanová, 1928) are monotypic genera whose identity is poorly understood and their taxonomic validity remains to be assessed. Furthermore, many species need to be redescribed, as their morphology is poorly known and sometimes their true identity is unknown or even misunderstood. Within our ongoing morphological and taxonomic reassessment of Western Palaearctic geophilids and attempts to rearrange species in uniform, putatively natural genera (e.g., Bonato et al., 2006; Bonato & Minelli, in press), we found compelling evidence for the existence of a distinct lineage that has previously not been recognised as a distinct taxon. It differs from all other geophilids in the very peculiar shape of the claws on the walking legs. After examination of representative specimens and critical evaluation of all published information, we analysed the morphology, taxonomic circumscription and geographical occurrence of this lineage and found that it deserves to be recognised as a distinct genus. This paper provides (i) a taxonomic description of this new genus, (ii) a critical analysis of the included species, (iii) a detailed redescription and illustration of the designated type species, (iv) an analysis and update of the geographical occurrence of the included species, (v) a description of the peculiar structure of the claws of the walking legs of these centipedes.


INTRODUCTION
According to the currently most followed systematic arrangement of the geophilomorph centipedes (Chilopoda Geophilomorpha), almost half of the known species in this group belongs to the single family Geophilidae (Minelli, 2006). With more than five hundred described species distributed throughout the world, geophilids represent a taxon only vaguely diagnosed and still in need of being more rigorously circumscribed within a phylogenetic framework.
The internal taxonomic arrangement of the geophilids also appears unsatisfactory. Within the fauna of the Western Palaearctic, where geophilids are highly diverse and most students have concentrated their investigations, the arrangement of species in genera deserves extensive revision: some genera (e.g., Geophilus Leach, 1814 andBrachygeophilus Brölemann, 1909) are still used by authors under very broad concepts, that encompass diverse and apparently composite assemblages of species; conversely, other nominal genera (e.g., Bebekium Verhoeff, 1941, Folkmanovius Dobroruka, 1957and Photophilus Folkmanová, 1928 are monotypic genera whose identity is poorly understood and their taxonomic validity remains to be assessed. Furthermore, many species need to be redescribed, as their morphology is poorly known and sometimes their true identity is unknown or even misunderstood. Within our ongoing morphological and taxonomic reassessment of Western Palaearctic geophilids and attempts to rearrange species in uniform, putatively natural genera (e.g., Bonato et al., 2006; in press), we found compelling evidence for the existence of a distinct lineage that has previously not been recognised as a distinct taxon. It differs from all other geophilids in the very peculiar shape of the claws on the walking legs.
After examination of representative specimens and critical evaluation of all published information, we analysed the morphology, taxonomic circumscription and geographical occurrence of this lineage and found that it deserves to be recognised as a distinct genus. This paper provides (i) a taxonomic description of this new genus, (ii) a critical analysis of the included species, (iii) a detailed redescription and illustration of the designated type species, (iv) an analysis and update of the geographical occurrence of the included species, (v) a description of the peculiar structure of the claws of the walking legs of these centipedes.

MATERIAL AND METHODS
After examination of large samples of geophilomorphs from private and museum collections, we identified 56 specimens from 40 localities as belonging to the new genus described here, and in particular to the species Geophilus conjungens Verhoeff, 1898. Specimens were examined using light microscopy and standard methods for clearing, temporary mounting and dissection of mouth parts of geophilomorphs (Pereira, 2000;Foddai et al., 2002). Leg claws of a representative specimen were examined using Environmental Scanning Electron Microscopy (XL30 Philips).
Even though we did not examine the type material of all relevant taxa, we tried to locate and examine that necessary for assessing morphological features and taxonomic status.
For the analysis of geographical distribution, all published and new localities and their current names were identified by browsing the Geographic Names Data Base of N.G.I.A. (http://gnswww.nga.mil/geonames/GNS).

RESULTS
Genus Diphyonyx gen. n.  Type species. Geophilus conjungens Verhoeff, 1898. Diagnosis. Geophilids with clypeus lacking finely areolate areas; labral side-parts partially distinct from the clypeus, bearing slender projections; first maxillae with two pairs of lappets; telopodites of the second maxillae with simple, pointed claws; forcipular coxosternum with a pair of anterior tubercles and complete chitin-lines; forcipular tarsungulum crenulated, with a small basal tubercle; trunk sterna without pores; on the legs of an anterior part of the trunk, claws swollen, the anterior spur of each claw enlarged into an elongate projection; sternum of the last leg-bearing segment wider than long; most coxal glands opening through a single pouch on the lateral margin of the sternum; telopodites of the last pair of legs slender in females, moderately swollen and densely hairy in males, provided with pointed claws.

Included species. Diphyonyx conjungens
Diagnostic characters of the Diphyonyx species are presented in Table 2.
Worth noting is that Verhoeff (1898: 350) states that his description of G. conjungens is based only on the two specimens listed above, but in the same paper refers 1% and 5& from "Cilicien" to this species (Verhoeff, 1898: 360). Also worth noting is that one specimen labelled "Paratypoid", from "Kleinasien", is preserved in the Zoologisches Museum Hamburg (Weidner, 1960).
Type locality. Both syntypes are most probably from Cilicia (Turkey), but the precise localities are unknown.
Material examined. Localities are listed by country and administrative unit, in alphabetic order, and are mapped in Fig.  11; the number of leg-bearing segments is given in parentheses for each specimen, whenever known; bibliographic references are given for localities already recorded in the literature; abbreviations for repositories are listed under "Material and Methods".
General features. Body slender, slightly narrowing anteriorly, more attenuated towards the posterior tip. Colour (preserved in ethanol) almost uniform, dark yellow.
Antennae. Each antenna slender, ca. 3 times as long as the head. Articles slightly, gradually narrowing and shortening from article II, which is ca. 1.2 times as long as wide, to article XIII, which is ca. 0.9 times as long as wide. Article XIV sub-ovoid, ca. 2.1 times as long as wide. Setae gradually more dense and shorter from the basal articles to the distal ones. Apical sensilla ca. 12 µm long, spear-like, slender, narrowing quite abruptly from about the mid-length. Club-like sensilla ca. 10 µm long, only on article XIV, grouped on the distal parts of both the internal and external sides. Three longitudinal rows of propioceptive spine-like sensilla at the bases of articles: 3-4 sensilla in each row on articles II-V, 2-3 sensilla in each row on articles VII-IX, 1-2 sensilla in each row on articles XI-XIII; rows lacking on articles VI, X and XIV, where only a single, dorsal sensillum is present.
Mandible. A single pectinate lamella. Maxillae I (Figs 2, 6). Coxosternum entire. Medial projections sub-triangular, longer than wide. Telopodite ca. 1.3 times as long as the medial projection, composed of two articles; tip rounded, covered with fine scales. Two pairs of lateral lappets, covered with scales, on the anterior corners of the coxosternum and basal articles of the telopodites, respectively.
Forcipular segment (Figs 1, 7). Tergum subtrapezoid, the lateral margins evidently converging anteriorly, ca. 2.3 times as wide as long. Exposed part of the coxosternum ca. 1.4 times as wide as long; a pair of dark, stout tubercles on the anterior margin (Fig. 3); coxopleural sutures entirely ventral and strongly converging posteriorly; chitin-lines well marked, reaching the condyles anteriorly. Basal article of the forcipule approximately as long as wide, the internal side shorter than the external side, without tubercles, only with two shallow bulges. Intermediate articles of the forcipule distinct, without tubercles, each only with a shallow bulge. Tarsungulum abruptly narrowing near the base, the distal part uniformly curved and narrowing; a basal, small tubercle; internal margin evidently crenulated (Fig. 4).
Leg-bearing segments. Tergum I wider than the subsequent one, the lateral margins slightly converging posteriorly; pretergum not exposed. Sternum I rounded anteriorly. Sterna from II to penultimate sub-rectangular; setae of various sizes, the longest arranged in two transverse rows; no trace of a "carpophagus" socket on the anterior margin, nor of a backward projection (condyle) on the posterior margin; no sternal pores. On the most anterior and most posterior segments, legs slender and claws slender, slightly curved and bearing two basal, tiny spines (spurs), one anterior to the other. From segment I to about XV, legs become gradually more swollen, the claws gradually larger, more swollen at the base and more evidently curved; the anterior spur becomes thicker and more elongate, and extends beyond the tip of the claw (Figs 9-10). From about segment XXV to about segment XXXV, legs, claws and spurs become gradually similar to those on the most anterior segments.
Last leg-bearing segment (Fig. 8). Pretergum ca. 3.5 times as wide as long, without apparent sutures on its dorso-lateral sides. Tergum ca. 1.1 times as wide as long, the lateral margins evidently convex and converging posteriorly, the posterior margin truncate. Sternum ca. 1.5 times as wide as long, the posterior margin evidently rounded. Coxal glands grouped on the anterior part of each coxopleuron, most of them opening through a longitudinally elongate pouch, on the ventral side of the coxopleuron, close to the lateral margin of the sternum; the most posterior gland opening through an independent, large pore on the posterior part of the ventral side of the coxopleuron; no pores opening on the dorsal side (Fig. 5). Telopodite ca. 1.6 times as long and slightly more swollen than the preceding one; all articles covered with long, scattered setae; ventral side of the most basal articles covered with short, dense setae. Claw well developed, curved and pointed, with only one basal, postero-ventral, tiny spur.  (Verhoeff, 1898), &, 33 mm long, from Geraki, Thrace, Greece; Environmental Scanning Electron Microscope (XL30 Philips, 15.0 kV) micrographs. 9 -claw of the left leg of the X leg-bearing segment, anterior side; 10 -claw of the right leg of the XXI leg-bearing segment, anterior side. n. from all other genera tentatively recognised in the subgroup of Geophilidae to which Diphyonyx belongs. Genera in this subgroup have only slightly elongated head and forcipules, coxosternum of the second maxillae without chitinised ridges, sutures between forcipular coxosternum and pleurites evidently converging posteriorly, forcipular tergum not evidently narrower than the subsequent tergum. This subgroup corresponds roughly to the Geophilinae sensu Attems (1929), but also includes probably some genera originally placed in the poorly diagnosed family Sogonidae (see Crabill, 1961Crabill, , 1968 Terminal segments (Fig. 8). Genital sternum inflated; gonopodal lamina uniformly curved, without an apparent median notch or sinuosity.
Last leg-bearing segment and terminal segments in the male (based on two adult males, 35 and 36 mm long, respectively, both with 75 leg-bearing segments, from the pass between Cankiri and Ilgtaz, Anatolia, Turkey; see above, under "Material examined"). Telopodites of the last pair shorter than in the female and moderately swollen. Claws of the last pair relatively thin and about three times shorter than in the female (occasionally much smaller, as observed in 3 adult males out of 15 examined). Gonopodes biarticulate and well separated, a sub-conic medial projection between the gonopodes. Geographical distribution. D. conjungens is recorded in the Balkan Peninsula between Macedonia and Thrace, throughout the entire Anatolia from the western coast and southern Sporades islands to the most eastern part of Turkish Armenia, northwards to the Pontic mountains and southwards to the Tauric mountains, and also in Crimea. See Fig. 11.

Diphyonyx sukacevi
Diagnosis is based on the original description only (Folkmanová, 1956).
Diagnostic characters of the Diphyonyx species are presented in Table 2.
Based on published information (Folkmanová, 1956), the specimens of the type series were given by M.S. Ghilarov (Laboratory of Soil Zoology of the Institute of Animal Morphology, USSR Academy of Sciences) to B. Folkmanová (at that time, at the Faculty of Science of the Masaryk University in Brno). At present, however, no specimen recognisable as belonging to such material is preserved in the Institute of Animal Morphology, Moscow, nor in the Zoological Museum of Moscow University where part of the collections of the former institute was transferred (A. Shileyko, pers. comm.), nor even in the Masaryk University in Brno, Czech Republic (K. Tajovský, pers. comm.); further, specimens retained in the personal collection of L.J. Dobroruka are possibly lost (K. Tajovský and I. Tuf, pers. comm.).
Geographical distribution. D. sukacevi is known from the most western part of the Caucasus range, north of the Black Sea, and from the Many valley, north of the Caucasus. See Fig. 11.
After the original description from two localities (Folkmanová, 1956), D. sukacevi has not been recorded again. Despite our examination of samples of geophilomorphs collected from both eastern Anatolia and the Caucasus, we have not found any specimen referable to this species.

Diagnosis.
A Diphyonyx species with ca. 2-4 slender filaments but without tubercles on the labrum, with evident condyles between the sterna of the anterior part of the trunk, and a posterior isolated pore in addition to the anterior pouch on each coxopleuron.
Diagnosis is based on the original description only (Folkmanová & Dobroruka, 1960).
Diagnostic characters of the Diphyonyx species are presented in Table 2.
Based on published information (Folkmanová & Dobroruka, 1960), the specimens of the type series were given by M.S. Ghilarov (Laboratory of Soil Zoology of the Institute of Animal Morphology, USSR Academy of Sciences) to B. Folkmanová and his student L.J. Dobroruka (at that time, at the Faculty of Science of the Masaryk University in Brno) and were deposited in the personal collection of L.J. Dobroruka. At present, however, specimens retained by L.J. Dobroruka are possibly lost (K. Tajovský and I. Tuf, pers. comm.), whereas no specimen recognisable as belonging to this material is preserved in the Institute of Animal Morphology, Moscow, nor in Zoological Museum of Moscow University, where part of the collections of the former institute was transferred (A. Shileyko, pers. comm.), nor even in the Masaryk University in Brno, Czech Republic (K. Tajovský, pers. comm.).
Geographical distribution. D. garutti is known from the most western part of the Caucasus range, north of the Black Sea. See Fig. 11.
After the original description from the type locality (Folkmanová & Dobroruka, 1960), D. garutti has not been recorded again. An examination of samples of geophilomorphs collected from both eastern Anatolia and the Caucasus did not find any specimens referable to this species.
Variation in segment number. Unknown.

Taxonomy
When Verhoeff (1898) described Geophilus conjungens, he provided an incomplete account of its morphology. In particular, he completely omitted to describe the unusual shape of the claws. This is not surprising, however, as the walking legs were usually not seen to be of Fig. 12. Number of leg-bearing segments in Diphyonyx conjungens (Verhoeff, 1898), based on both published and unpublished data (n = 53). diagnostic value in the systematics of geophilomorphs (but see Attems, 1959). Verhoeff did not discuss explicitly the taxonomic position of G. conjungens and referred the species to the large and ill-defined genus Geophilus Leach, 1814. Even though the species was recorded again (Attems, 1929;Verhoeff, 1941;Zapparoli, 1994Zapparoli, , 1999Zapparoli, , 2002Misirlioglu, 2003), these contributions did not provide a better understanding of its morphology and taxonomic position. G. conjungens was either kept in Geophilus, according to the traditional broad concept of this genus, or moved to Brachygeophilus, a composite assemblage of geophilid species based mainly on the shared absence of sternal pores, most probably a homoplastic trait (Turcato et al., 1995;Foddai & Minelli, 2000).
Brachygeophilus sukacevi and its subspecies garutti are described in two rather obscure papers written in Russian (Folkmanová, 1956;Folkmanová & Dobroruka, 1960). No other specimens were subsequently referred to these taxa, which were almost completely ignored in the subsequent literature, so that their taxonomic position remained to be assessed. Indeed, Folkmanová (1956) commented on the similarity between B. sukacevi and G. conjungens and contrasted the two species in a comparative table. To date, howerer, these two species have not been recognised explicitly as taxonomically related.
After evaluating and integrating all the published information and evidence obtained by examination of representative specimens, it was found that conjungens, sukacevi and garutti are closely related taxa and deserve to be regarded as members of a distinct genus. They share a combination of morphological traits, which is unique to geophilid genera, including all nominal genera of uncertain identity. Among these traits are the general shape and pattern of tubercles on the forcipules and forcipular coxosternum, some features of the trunk sterna, the shape of the claws of the walking legs and the arrangement of coxal glands. A phylogenetic analysis is beyond the scope of this paper and its effectiveness would be limited by the inadequate knowledge available on some geophilid genera. However, conjungens, sukacevi and garutti constitute most probably a monophyletic group, as they share a unique, highly derived shape of claw. Other possible synapomorphies, which are found also in other lineages of geophilids but most probably originated independently, are the evident crenulation of the forcipular tarsungula, the lack of sternal pores and the aggregation of most coxal glands into a common pouch. Our proposal to give this lineage genus status is consistent with current practice in geophilomorph taxonomy, as it is based on characters that are usually given a highly diagnostic value at the genus level. Even though the phyletic position of this lineage relative to other geophilid genera is uncertain, no evidence points to a close relationship of conjungens, sukacevi and garutti with the type species of either Geophilus or Brachygeophilus, and therefore their inclusion in these two genera appear unjustified. Instead, distinguishing Diphyonyx from both Geophilus and Brachygeophilus contributes to a more appropriate circumscription of these two currently composite genera.
We assessed the morphology and geographical distribution of D. conjungens by examination of representative specimens from a wide region spreading from Greek Macedonia to Turkish Armenia. All these specimens were confidently placed in the single species D. conjungens as they all have the morphological traits described by Verhoeff (1898) as diagnostic for G. conjungens, but not the putative differential characters described by Folkmanová (1956) andDobroruka (1960) for either B. sukacevi or B. sukacevi garutti. In contrast, our taxonomic evaluation of both D. sukacevi and D. garutti is based on published accounts, because we were not able to locate the type specimens of these taxa (see remarks under "Type material" of both taxa), nor other specimens referable to them.
Putative differential characters between the three taxa conjungens, sukacevi, and garutti are the presence and number of tubercles and slender projections on the labrum, the presence vs. absence of evident condyles between the sterna on the anterior part of the trunk, and the presence vs. absence of an isolated coxal pore in addition to the common pouch (see Table 2). Worth noting is that Folkmanová (1956), relying on Verhoeff's description of G. conjungens, cites the presence of two pairs of lappets on the first maxillae and the peculiar shape of the claws as distinguishing his B. sukacevi from G. conjungens; however, Verhoeff's account is inaccurate on these points, as both traits in D. conjungens correspond to those described in B. sukacevi. Even though the actual morphological difference between B. sukacevi, B. sukacevi garutti and G. conjungens remains to be assessed, the available information appears to indicate that B. sukacevi and B. sukacevi garutti are taxonomically distinct from G. conjungens. Furthermore, even though garutti was originally described as a subspecies of sukacevi and this treatment was never disputed, garutti is given species rank here because (i) there is no evidence that garutti is more closely related to sukacevi than to conjungens, and (ii) the two putative subspecies were originally described from very close localities, only a few dozen kilometres apart, within a region lacking any apparent biogeographical barriers, so that an intraspecific differentiation appears unlikely.
Twelve other nominal species of geophilids, from either Anatolia or the western part of North America, are described under Brachygeophilus (Chamberlin, 1938(Chamberlin, , 1941(Chamberlin, , 1952. They are B. anonyx Chamberlin, 1941, B. delotus Chamberlin, 1941, B. erzurumensis Chamberlin, 1952, B. eudontus Chamberlin, 1952, B. honozus Chamberlin, 1952, B. leionyx Chamberlin, 1938, B. mundus Chamberlin, 1952, B. oregonus Chamberlin, 1941, B. orientis Chamberlin, 1952, B. simoporus Chamberlin, 1952, B. transitus Chamberlin, 1941and B. yavapainus Chamberlin, 1941. The original assignment of these species to Brachygeophilus was mainly based on the lack of sternal pores, a character shared with the type species B. truncorum; however, the true identity and taxonomic position of these species remains to be assessed. After evaluation of all published information and examination of the type material of some of these species from Turkey (B. erzurumensis, B. eudontus, B. mundus; preserved at the National Museum of Natural History, Washington), it was concluded that none of these species should be included in Diphyonyx, even though the taxonomic position of most of them remains uncertain.

Morphology of the leg claws
In Diphyonyx, the shape of the pretarsus of the walking legs varies greatly along the trunk and, in particular, is highly modified in a series of about a dozen pairs of legs on the anterior half of the trunk. The shape of all other pairs conforms to that usually present along the whole trunk of other geophilids: the pretarsus bears a single claw, which is relatively slender and only slightly curved; two needle-like, straight spurs (also called accessory spines or parungues) emerge from the claw, on the ventral side, close to the basal articulation of the pretarsus, one anterior to the other; both spurs are evidently narrower and shorter than the claw and are similar to each other. Unlike in other geophilids, however, in Diphyonyx the shape of the pretarsus changes gradually but dramatically from both the most anterior and posterior segments towards those on the anterior half of the trunk: the claw increases in size, becoming more swollen and more evidently curved; the anterior spur becomes an approximately cylindrical projection, only slightly tapering, with rounded tip, and extends beyonds the tip of the claw; the posterior spur, however, remains relatively small.
This peculiar shape and pattern of variation in the claws is most probably present in all specimens of all species of Diphyonyx of both sexes, and not only in adults but juveniles as well. Even though not previously described for D. conjungens, we found it in all 56 specimens examined of both sexes and different sizes. As for D. sukacevi and D. garutti, it was reported by Folkmanová (1956) in all of 31 specimens of Brachygeophilus sukacevi, and Folkmanová & Dobroruka (1960) in all of 23 specimens of Brachygeophilus sukacevi garutti.
The function of these peculiar claws remains unknown. We refrain from speculation, pending observations on living specimens and information on the ecology of Diphyonyx. Worth noting is that early records suggest D. conjungens is a littoral species (Verhoeff, 1941), but it was subsequently recorded at many inland sites, up to 1800 m (see above, under "Material examined").
Even though a slight variation in the size and some minor morphological features of the walking legs along the trunk is common in geophilids, the highly derived shape of the claws observed in Diphyonyx is unprecedented in the family. Worth noting, however, is that a similar pattern of longitudinal variation, with a similar modified morphology of the claws, is documented for two other lineages of geophilomorphs, both of uncertain phyletic position but obviously only distantly related to Diphyonyx. One of these lineages comprises Neogeophilus Silvestri, 1918 andEvallogeophilus Silvestri, 1918, two strictly related genera traditionally recognised as belonging to a distinct family Neogeophilidae, which includes four species found only in Central America (Silvestri, 1918;Crabill, 1961Crabill, , 1969. The other lineage comprises the single genus Eucratonyx Pocock, 1898, which is variously classified in distinct family Eucratonychidae or within the Gonibregmatidae, and includes two species found only in South-Eastern Asia (Pocock, 1891(Pocock, , 1898Ribaut, 1912;Attems, 1914;Silvestri, 1919). In both these lineages, as in Diphyonyx, there is a longitudinal gradient in the overall enlargement of the claws and the hypertrophic growth of the anterior spur, with the centre in a sub-anterior region of the trunk. Worth noting is that the similarity between the claws of B. sukacevi and those of neogeophilids and Eucratonyx was noted by Folkmanová (1956), andCrabill (1969) proposed the term "fibulunguis" for this kind of biramous pretarsus. The modified pretarsi of the neogeophilids and Eucratonyx, however, differ from those of Diphyonyx in the overall shape of the additional projection and other features of the claw. The function of these pretarsi in Diphyonyx remains obscure, even though Crabill (1961,1969) speculated that they function as anchoring devices in locomotion. In addition to these two lineages, where the pretarsi have been examined and illustrated in detail, modified claws were detected by Crabill (1961Crabill ( , 1969) in a few other genera, namely the himantariid Bothriogaster Selivanov, 1879, the schendylid Pectiniunguis Bollman, 1889 and the gonibregmatid Sogophagus Chamberlin, 1912, but their actual shape has not been described in detail.