The mostly cavernicolous millipede genus Stygiiulus Verhoeff, 1929, stat. nov.: taxonomy, distribution and phylogenetic relationships (Diplopoda, Julida, Julidae) Author Vagalinski, Boyan CF6A5691-5C32-4CFF-9EB6-045DEB16F289 Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, 2 Gagarin Street, 1113, Sofia, Bulgaria. boyanv84@gmail.com Author Borissov, Simeon C035E1AC-D4FB-4A3F-8B38-5D38A9665E88 Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, 2 Gagarin Street, 1113, Sofia, Bulgaria. borissovsb@gmail.com Author Bobeva, Aneliya 0F4EA315-46BE-49AC-8FB4-CF710C5B2451 Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, 2 Gagarin Street, 1113, Sofia, Bulgaria. aneliabobeva@gmail.com Author Canciani, Giacomo 4BB21FD2-15C8-44BD-907A-4498D7D02A15 Jamarski Klub Kraški Krti / G. S. Talpe del Carso, loc. San Michele del Carso / Vrh, I- 34070 Savogna d’Isonzo (GO), Italy. & Associazione Speleologica Forum Julii Speleo, Via Carraria 99, I- 33043 Cividale del Friuli (UD), Italy. giacomo.canciani90@gmail.com Author Antić, Dragan Ž. 2368C980-2042-4137-998D-8C91E4337185 University of Belgrade - Faculty of Biology, Institute of Zoology, Studentski Trg 16, 11000 Belgrade, Serbia. & Serbian Biospeleological Society, Trg Dositeja Obradovića 2, 21000 Novi Sad, Serbia. dragan.antic@bio.bg.ac.rs text European Journal of Taxonomy 2022 2022-02-28 798 30 69 http://dx.doi.org/10.5852/ejt.2022.798.1669 journal article 20422 10.5852/ejt.2022.798.1669 31fec661-5dac-4626-856d-4ba4680efee7 2118-9773 6323002 50692D26-A41C-4F85-B207-A6747FD07470 Stygiiulus illyricus ( Verhoeff, 1929 ) comb. nov. Figs 10B , 11B , 13 Typhloiulus ( Stygiiulus ) illyricus Verhoeff, 1929: 20–23 , fig. 1. Typhloiulus ( Stygiiulus ) illyricus – Manfredi 1932: 81 . — Strasser 1962: 20 , 35–36, figs 11i, 36–37. Fig. 6. Stygiiulus gentianae (Strasser, 1971) comb. et stat. nov. , ♂ from Grotta [cave] della Vecchia Diga (NHMD). A . Right promere, caudal view. B . Right mesomere, oral view. C . Distal part of left opisthomere, mesal view. Abbreviations: ab = anterior branch of solenomere; el = external lobe; il = internal lobe; pb = posterior branch of solenomere; ph = posterior hump; v = velum. Scale bars = 0.05 mm. Typhloiulus illyricus – Verhoeff 1930: 17 . — Antić et al. 2018: 263 , fig. 3. Typhloiulus illyricus stygis – Verhoeff 1933: 15–17 , figs 28–29, syn. nov. Typhloiulus illyricus var. obscurus – Verhoeff 1933: 17 . Typhloiulus illyricus var. obscura – Wolf 1934 –38: 515. Material examined SLOVENIA • 2 topotype juvs ; Ocizla , Beško-Ocizeljski System (= Ocizeljska Jama Pit ); 19 Apr. 2012 ; T. Delić leg.; D. Antić det. 2018; IZB • 1 ♂ , 1 ♀ ; Dane , Divača , Mejame Pit (= Med jamah, Medjama ); 22 Apr. 2014 ; M. Zagmajster leg.; D. Antić det. 2018; IZB . CROATIA • 1 ♂ , 1 ♀ ; Istria , Ročko polje , Roč , Rabakova Cave ; 30 Jun. 2013 ; D. Šuperina leg.; D. Antić det. 2018; IZB • 1 ♀ ; same collection data as for preceding; 16 Apr. 2013 ; IZB . Diagnosis A species of Stygiiulus with normal mouthparts. Distinguishable from congeners by the combination of certain gonopodal characters ( Fig. 10B ), viz., a mostly straight promere, a mesomere with the apex bent frontad, and an opisthomere with a small but distinct posterior hump, a broad and deeply serrated velum, and a vestigial posterior solenomeral branch, this being completely fused to the velum. Descriptive notes ANTENNAE. 2.2 times as long as head and ca 1.8 times as long as H in males, and 1.7 times and ca 1.5– 1.55 times, respectively, in females; antennomere 5 ca 2.4 times as long as broad; antennomeres 2–5 subequal in length, ca 1.3–1.4 times as long as 6. TARSUS OF MID- BODY LEGS. Ca 2.4 times as long as tibia and ca 2 times as long as apical claw. Mid-body legs ca 1.1 times as long as H in both sexes. FEMALE SEXUAL CHARACTERS. Leg-pairs 1 and 2 considerably shorter than, but as thick as, following legs. Vulva ( Fig. 11B ) slightly compressed in the sagittal plane, mostly symmetric; median cleft deeper than in most congeners; each valve of bursa with several, mostly vertically arranged setae, 1–2 setae on side sclerites; operculum (op) distally markedly thickened, with a concave apical margin, exceeding bursa by slightly more than ¼ of total height of vulva, medio-laterally with two longitudinal rows of setae each side, with a bunch of setae on each latero-apical corner. Receptaculum seminis consisting of a fine, slightly bent, mesal tube (mt) ending in a small piriform ampulla (ma), and a somewhat shorter lateral tube (lt) ending in an ampulla (la) of similar shape and size as the former one. Distribution Known exclusively from caves and pits in the Istrian Peninsula in Croatia and the northwestern Dinarides in Slovenia ( Fig. 13 , green squares). Remark From Rabakova Cave, Verhoeff (1933) described the subspecies illyricus stygis , mentioning the possibility that the observed differences between the single male his description was based upon and the typical illyricu s were due to periodomorphosis, but he nevertheless opted to give a formal name to the new morph. Indeed, the gonopods he drew seem to be underdeveloped (see Verhoeff 1933: 20 , fig. 28). Fortunately, we examined here one adult male from Rabakova Cave, whose gonopods appeared completely identical to the gonopods of the typical illyricus . We were even luckier to find that one of the juveniles from the type locality of the typical illyricus was a subadult male with unmodified first pair of legs. The gonopods of this subadult male are very similar to Verhoeff's (1933) drawing of the gonopods of the subspecies stygis . Based on these observations, it is clear that Verhoeff's stygis was actually a non-adult male or “Junior- Männchen” [junior male] – a term coined by Strasser (1971b) , referring to typhloiulinine males with almost fully developed gonopods, but with non-modified first pair of legs and other, less conspicuous, underdeveloped external somatic structures (see also Vagalinski et al. 2015 ). We thus consider here S. illyricus stygis syn. nov. as a junior subjective synonym of the typical S. illyricus comb. nov.