Spelaeodiscus Brusina, 1886

Pall-Gergely, Barna, Deli, Tamas, Eross, Zoltan Peter, Reischuetz, Peter L., Reischuetz, Alexander & Feher, Zoltan, 2018, Revision of the subterranean genus Spelaeodiscus Brusina, 1886 (Gastropoda, Pulmonata, Spelaeodiscidae), ZooKeys 769, pp. 13-48 : 13

Genus Spelaeodiscus Brusina, 1886

Patula (Spelaeodiscus) Brusina, 1886: 37.

Type species.

Helix Hauffeni Schmidt, 1855.

Distribution.

The genus Spelaeodiscus has a disjunct distribution. One species ( S. hauffeni ) is only known from Slovenia, whereas the rest of the genus is distributed in the vicinity of the Skadar Lake Basin (also known as Shkodër Lake or Skutari Lake) in Montenegro and northern Albania (Figure 2 ).

Included taxa.

Spelaeodiscus albanicus albanicus (A. J. Wagner, 1914), S. albanicus edentatus Páll-Gergely & P. L. Reischütz, ssp. n., S. dejongi Gittenberger, 1969, S. densecostatus Páll-Gergely & A. Reischütz, sp. n., S. hauffeni (Schmidt, 1855) S. hunyadii Páll-Gergely & Deli, sp. n., S. latecostatus Páll-Gergely & Erőss, sp. n., S. obodensis Bole, 1965. S. unidentatus unidentatus Bole, 1961, S. unidentatus acutus Páll-Gergely & Fehér, ssp. n., S. virpazarioides Páll-Gergely & Fehér, sp. n. For key traits see Table 1 .

Delimitation of this genus.

The reproductive anatomy of Spelaeodiscus and Aspasita is characterized by a short penial caecum, a well-developed penial appendix, sometimes an epiphallic caecum, and a bursa copulatrix without a diverticulum. The retractor muscle is divided into two bounds, one inserting on the penial appendix, whereas the other at the base of the penial caecum. Examining the anatomical descriptions and drawings of Spelaeodiscus ( Bole 1965) and Aspasita ( Hudec 1965, Gittenberger 1975, Schileyko 1998, Subai and Dedov 2008), we were unable to find characters that would constantly differ between the two groups. For example, the penial caecum was long and slender in A. tatrica (see Hudec 1965) and S. hauffeni (see Bole 1965), but was short and conical in A. triaria (see Subai and Dedov 2008) and S. unidentatus (see Bole 1965). Also, the shape of the bursa and the position of the starting point of the penial appendix was greatly variable across genera. Clear epiphallic caecum was only found in S. hauffeni , but some thickening was visible in S. unidentatus and A. triaria .

As for shell characters, Spelaeodiscus is characterized by a mostly colourless shell that is smaller than 4.3 mm (majority of species are even smaller than 3.5 mm), the spire is relatively low (height of body whorl at least two third of the height of the entire shell), the body whorl is evenly rounded, the edge of the parietal callus is straight, and the peristome is only slightly expanded. In contrast, Aspasita shells are brownish, larger than 4.3 mm, they have higher spire (height of body whorl is approximately half of the height of the entire shell), the shell is shape reverse trapezoid from standard apertural view, the callus is heart-shaped, and the basal part of the peristome is strongly expanded.

The habitat was the only “trait” mentioned by Gittenberger (1969) as difference between the two groups. Namely, Spelaeodiscus is subterranean, whereas Aspasita can be found on rock surfaces and among leaf litter at the base of limestone rocks. In the lack of sound molecular data it is difficult to infer their relationship, but based only on ecological, conchological, and biogeographical differences it seems reasonable to keep Aspasita and Spelaeodiscus as distinct genera.

Figures

Figure 2. Distribution of the genus Spelaeodiscus Brusina, 1886.