Bioacoustics of Diplocephalus

Species of Diplocephalus with uncertain assignment Diplocephalus permixtus is also a “ Diplocephalus ” in the strict sense following our diagnostic characters, i.e., having the specific enlarged dorsal radical process (character 142). However, it emerged between the cristatus - and the pavesii -group, sharing the narrow cephalic PME lobe with the cristatus- group. Diplocephalus turcicus , which emerged at node 51, might also be associated with the graecus -group by having a less distinct ventral radical process and curved spermathecae, located at the anterior side of the epigyne. Additionally, D. turcicus has a relatively special prolateral tibial apophysis with a tooth emerging from it at its retrolateral side ( Brignoli 1972 : fig. 15) and superficially similar to Savignia kawachiensis ( Oi 1960 : fig. 157). Bosmans et al. (2009 : figs 7–12) illustration of D. turcicus seems to correspond to A. rhodes based on the male palp and the epigyne conformation, and the location record also from an island in Greece . Diplocephalus picinus (node 61) appears within the Araeoncus clade (node 59) ( Figs 25–26 ). However, this species is problematic as it changes position through different analyses (Supp. file 2, Supp. file 3), most likely because of its singular palp morphology. As its position is unstable, we leave it provisionally in Diplocephalus . Within node 39 are two well-supported nodes corresponding to Savignia (node 45) and Hemistajus (node 43). The three remaining taxa in this clade are problematic: D. uliginosus , D. lusiscus and D. subrostratus . Diplocephalus lusiscus appears within node 39 ( Fig. 25 ) which might be correct at least based on the embolic division that shares some similarities with other members in node 39, especially the flattened embolus. However, D. lusiscus is a cave dweller ( Wiehle 1963 ) with morphological adaptations to that habitat that have led to some derived characters that are difficult to homologise. The same is true for the cave dwelling Savignia rostellatra Song & Li, 2009 with very derived characters of the embolic division (see Savignia section) but no obvious morphological adaptations to cave dwelling ( Song & Li 2009 ). Diplocephalus uliginosus seems to be a simpler type of Hemistajus concerning the form of the cephalic lobe that resembles many members of Erigonella (e.g., Fig. 15C, F ) while the other species in Hemistajus have diagonally flattened cephalic fronts ( Fig. 15B ). Also, the simpler prolateral tibial apophysis and the unmodified triangular dorsal radical process underline the basal position of D. uliginosus with respect to the other species of Hemistajus . Diplocephalus subrostratus probably belongs to Hemistajus , and was thought to be very similar to D. picinus (e.g., Eskov 1988 ) but differs in its embolic division. In our phylogeny, both species emerge well separated from each other ( Fig. 25 ). Diplocephalus subrostratus is also very similar to D. uliguinosus but even simpler; it lacks any radical processes on the embolic division, has smaller suprategular apophyses and lacks a protruding inner margin of the epigyne ( Eskov 1988 : figs 42, 44). However, the curved, slightly elongated spermathecae, the diagonally flattened cephalic front and the inwards turned prolateral tibial apophysis ( Eskov 1988 : figs 40, 43) resemble very much to what is found in, e.g., D. montanus ( Eskov 1988 : figs 25, 28). According to Denis (1952) , D. caecus Denis, 1952 , a cave dweller from Romania , is very close to D. lusiscus . The form of the cephalic lobes, the arrangement of the eyes in the males of both species, and the male prolateral tibial apophysis are very similar. There are also two eyeless species from caves from Morocco , D. inanis Tanasevitch, 2014 and D. bosmansi Lecigne, 2025 . Diplocephalus bosmansi resembles D. picinus but with a broader epigynal fissure. Diplocephalus inanis males can be distinguished by the broad prolateral tibia and a curved embolus and females by the thick seminal ducts and wide epigynal fissure in the proximal part of the ventral plate, similar to D. picinus . Diplocephalus protuberiscus Wunderlich, 2022 is known from the male and is named based on the similarities to A. protuberans comb. nov. and D. lusiscus . It has a cephalic part raised with a setose clypeus like in Hemistajus and Savignia , a palpal tibia with a retrolateral branch, and a thick and curved embolus. The associations of D. montaneus Tanasevitch, 1992 , D. bifurcatus Tanasevitch, 1989 , D. hispidulus Saito & Ono, 2001 and D. sphagnicola Eskov, 1988 , that are likely not closely related to each other, remain obscure. Tanasevitch (1989) mentions the close resemblance of D. montaneus with D. cristatus . However, the lack of an enlarged dorsal radical process argues against a close relationship. Diplocephalus sphagnicola has a very distinct ventral radical process and a particularly long embolus ( Eskov 1988 : fig. 33) with a corresponding long copulatory duct in the female ( Eskov 1988 : fig. 37). Both characters are not found in any other group of taxa apart from maybe Araeoncus to which D. sphagnicola is presumably not closely related due to the lack of synapomorphic characters. Diplocephalus circularis Irfan, Zhang & Peng, 2025 and D. tongrenensis Irfan, Zhang & Peng, 2025 are two species recently described from China . Based on the median fissure, the wide copulatory opening of the epigyne and the long and spiral embolus in D. circularis , they probably belong to another genus of the Savignia genus group. Diplocephalus parentalis Song & Li, 2010 is closely related to D. hispidulus based on the palpal tibial apophysis shape, which is also covered by papillae (similar to several species of Erigonella ) and the complicated dorsal plate of the epigyne ( Song & Li 2010 : figs 9–11). It was placed in Diplocephalus based on the long copulatory ducts and it has a particular embolic division with a large radix with a sclerotised margin with no apophyses. The lack of a radical process on the radix and the different shape of the ventral plate with a “column-shaped complex” anteriorly, indicates that it does not belong to Diplocephalus and probably corresponds to another genus of the Savignia genus group. Diplocephalus machadoi Bosmans & Cardoso, 2010 males occur in two forms. In one, the cephalic PME lobe is very similar to D. picinus and the other has a pointed AME lobe that resembles to the one of A. galeriformis . It shares characters with species from different genera of the Savignia genus group and cannot be assigned to any based on the available figures. Species of Diplocephalus misplaced in the Savignia genus group Diplocephalus gravidus Strand, 1906 does not belong to the Savignia genus group due to the lack of a bisected epigyne ( Ono et al. 2009 : fig. 238) that is synapomorphic for this node (21). Therefore, it does not belong to Diplocephalus and presumably not to any other genus in the Savignia- group. Only the female is known from this species and compared to the other taxa included in the current analysis, it has a slightly elevated cephalothorax ( Ono et al. 2009 : fig. 236). Diplocephalus bicurvatus Bösenberg & Strand, 1906 also lacks the bisected epigyne ( Bösenberg & Strand 1906 : pl. 12 fig. 272e) and the prolateral tibial apophysis is more pronounced than in other Savignia- group members and is initially facing dorsally. The embolic division is also very different from what is found in any Savignia- group species ( Ono et al. 2009 : figs 230–234). The epigyne of D. culminicola Simon, 1884 seems to lack a median fissure ( Denis 1953 : figs 6–7) and therefore is most probably not a Savignia- group member. The current information on D. tiberinus ( Caporiacco, 1936 ) is restricted to one figure showing the male palp in Caporiacco (1936 : fig. 3) and a description in Latin, which are not sufficient for any discussion of generic assignment.