Stygiiulus Verhoeff, 1929

Vagalinski, Boyan, Borissov, Simeon, Bobeva, Aneliya, Canciani, Giacomo & Antić, Dragan Ž., 2022, The mostly cavernicolous millipede genus Stygiiulus Verhoeff, 1929, stat. nov.: taxonomy, distribution and phylogenetic relationships (Diplopoda, Julida, Julidae), European Journal of Taxonomy 798, pp. 30-69 : 33-34

Genus Stygiiulus Verhoeff, 1929 stat. nov.

Stygiiulus Verhoeff, 1929: 20 (as subgenus of Typhloiulus Latzel, 1884 ).

Alpityphlus Strasser, 1967: 146 , syn. nov.

Type species

Typhloiulus (Stygiiulus) illyricus Verhoeff, 1929 (by monotypy)

Diagnosis

A genus of blind Julidae characterized by a flagellum-bearing promere, a true mesomere, and an opisthomere with a well-developed velum. Differing from other blind leptoiulinine/typhloiulinine genera by the following combination of characters: promere with an internal and an external lobe on caudal face, both without setae; opisthomere rather slender, devoid of any distinct processes on caudal and lateral side, and possessing a lamellar, marginally often (but not always) serrated or ciliate velum and an apically bifid solenomere (one or both solenomeral branches vestigial in some species), with the exception of (some variations of) S. tobias (Berlese, 1886) comb. nov. in which the solenomere apically possesses a minute third branch behind the main two; and hypoproct either blunt or rounded, tightly fitting under paraprocts in both sexes.

Characterization

– Small (L from 10 mm) to large (L up to 70 mm) Julidae .

– Colouration pallid to light brown-grey.

– Ommatidia absent.

– Ozopores set considerably (rarely closely) behind pro-metazonal suture.

– Epiproct present, varying from short to very long, mostly straight.

– Hypoproct rounded or subtriangular, not or only insignificantly protruding behind rear contour of paraprocts, ventrally setose.

– Male mandibular stipites not expanded.

– Male walking legs ventrally with a well-developed adhesive pad on tibia at least in more frontal leg-pairs, some species also with a less pronounced pad on postfemur.

– Male pleurotergum 7 with expanded ventral margin forming a rather weakly pronounced lobe in its caudal section.

– Penis (not observed in S. seewaldi comb. nov.) long and slender, with short and stout apical lobes and fine, narrow terminal lamellae.

Gonopods

– Slender, solenomere more or less exceeding both pro- and mesomere in height.

– Promere roughly oar-shaped, with more or less well-developed internal and external lobe, these not bearing setae.

– Mesomere usually subequal to (rarely significantly shorter than) promere.

– Opisthomere simple, rather elongate, lacking paracoxal or other processes in its proximal or middle part, some species with a characteristic posterior hump at mid-distal level; subapically on frontal side with well-developed lamellar velum with often serrated or fringed margin; solenomere apically divided in two (rarely three) small branches – an anterior and a posterior one – with their tips often bearing several minute thread-like filaments; some species with one or both branches very weakly pronounced, difficult to detect.

– Basal spine at flagellum channel, with some exceptions (see below), usually absent.

Vulva (not observed in S. seewaldi comb. nov.)

– Operculum higher than bursa. – Median cleft of bursa shallow. – Receptaculum seminis consisting of two narrow and short (in relation to size of vulva) tubes (except for S. tobias comb. nov. in which both tubes are rather long), sometimes forming distinct ampullas at bottom.