Neobisium spelaeum

Judson, Mark L. I., 2012, Nomenclatural problems associated with the generic names Obisium Leach, 1814, Blothrus Schiödte, 1847 and Neobisium Chamberlin, 1930 (Arachnida: Chelonethi), Zootaxa 3475, pp. 21-35 : 30-31

Identity of Neobisium spelaeum

In their application, Harvey & Mahnert (2011) cite Ćurčiċ (1988) for a modern description of Neobisium spelaeum . However, that description was based on material from caves in Croatia that are situated more than 100 km (Mijatova Jama) or 350 km (Uporna Jama) from the type locality. Moreover, Ćurčiċ (1988) noted differences between his specimens and the description provided by Beier (1963). The latter was largely reproduced from that provided earlier by Beier (1932), which may have been based on material that Beier (1928) had identified from the type locality. Thus it is not certain whether the specimens described by Ćurčiċ (1988) really belong to this species. I have examined two specimens from the type locality: 1 ♂, 1 ♀, [ Slovenia], Krain, Adelsberger Grotte [= Postojna cave], leg. J. Sever, 1901 ( MNHN). These differ from Ćurčiċ’s (1988) description of N. spelaeum in having fewer teeth on the chelal fingers (fixed finger with 74–86, versus 94; movable finger with 66–73, versus 81), fewer setae on genital sternite II of the male (26, versus at least 36 [“21–46 anterior and 15–22 posterior setae”]), non-furcate subterminal setae (perhaps only a difference of interpretation) and in being slightly smaller in size. On the contrary, the specimens from Postojna cave agree well with material from the cave of Volčja jama (about 55 km SE of Postojna) that Mahnert (1974) described under the name N. stygium Beier, 1931 . It is worth noting in this respect that the group of 28 setae behind the male genital opening is in addition to the 25 + 2 × 3 setae reported by Mahnert (1974) in the sternal formula, thus giving a total of 53 + 2 × 3 setae on sternite III (V. Mahnert, in litt.), which is practically the same as the number observed in the topotype male of N. spelaeum (54 + 2 × 3). Also, contrary to Beier’s (1932, 1963) descriptions, coxa of leg I bears a process in N. spelaeum ( Figs 3–4 ). Because the process is thin-walled and small, it could easily be overlooked, particularly if the coxa is observed obliquely. It would appear that either N. stygium is a synonym of N. spelaeum or that Mahnert’s material was misidentified. In either case, it seems likely that the species-group taxa Mahnert (1974) synonymized with N. stygium (viz. N. meuseli Beier, 1931 , N. stygium paedwithi Beier, 1939 and N. stygium csikii Beier, 1939 ) are synonyms of N. spelaeum . However, it would be better to wait for a detailed comparison of material from the type localities of N. spelaeum and N. stygium before making any formal nomenclatural changes.

Examination of the topotypic material confirms the statement by Vachon & Gabbutt (1964) that the rallum of N. spelaeum has the same form as that seen in other species Neobisium . The ralli of the two specimens have 7–10 blades, of which only the two distal blades are denticulate ( Fig. 5 ).

Figures

FIGURES 2 – 5. Neobisium spelaeum (topotype male). 2, Anterolateral process of coxa of right leg I, ventral view. 3, Anteromedian process of coxa of right leg I, ventral view. 4, Coxa of right leg I, ventral view. 5, Rallum of left chelicera (sixth blade broken), ventral view; also shown are part of base of movable finger and basal blades of serrulae. Abbreviations: k paraxial condyle; MF movable finger; s. e serrula exterior; s. i serrula interior. Scale lines: 0.1 mm (figs 2 – 3), 0.2 mm (fig. 4), 0.05 mm (fig. 5).