Szabó János szerk.: Fragmenta Mineralogica Et Palaentologica 26. 2008. (Budapest, 2008)

the type species (as ideal solution) or in a doubtlessly Discohelix species to resurrect the family by its original diagnosis. Until reliable and satisfactory knowledge will have been available about the shell structures of the euomphalomorph genera, the writer of these lines thinks better to keep Discohelix and the related genera in a morphologically more familiar space that is given in the Euomphalina, not in Trochina. The shell-morphological characters are not contradictory to those of the Euomphaloidea, to which these genera were traditionally ascribed. Because NÜTZEL (2002) has demonstrated, in contrast to B

ANDEL & FRYDA's (1998) opinion, that the euomphalid protoconchs do not differ substantially from the "archaeogastropod type", identifiable also in Discohelix and in its relatives, momentarily no verified character gives satisfactory support to exclude these genera from the "traditional" systematical environment. At the same time these authors raised the rank of the taxon, containing Euomphalus and the related genera quite high, either to subclass (BANDE!

. & FRYDA 1998) or to order (NÜTZEL 2002) level. Both of these evaluations well reflect that there is a gastropod group of early appearance, which represents important phases in the gastropod evolution. It shows a rather high morphologic flexibility that might have been concomitant also with high shell structure variability along evolutionär}

7 lines towards derived groups. This possibility is supported by NÜTZEL (2002) paper that has demonstrated a three-layered shell structure in an Fiuomphalus species. All layers are consisted of calcite but NÜTZEL states that the two inner ones have been originally aragonite, without suggestion for the crystal modification, and the outermost one has been calcite. This would apparently mean the discovery of a second, but rather different structure in a single genus after MORRIS & CLEEVELY's (1981) two layered Euomphalus shell. Existence of so different structures in one genus does not seem really feasible. However, appearance of more than one shell structure types in an early, major group of gastropods (like Euomphalina), that is inferably ancestral (root) for some main gastropod evolutionary lines, seems a more realistic idea. Therefore a systematic place for the "discohelicid" genera, even with verified nacreous shell, in Euomphalina seems a better solution than to force them into a foreign morphospace, like that of Trochoidea as suggested by SCHRÖDER (1995). The trochoidean systematical place was questionably accepted by CONTI & MONARI (2002) when the nacreous shell structure in Discohelicidae had yet seemed to be verified. Their second alternative, to give superfamily rank (in Trochina) to this group of genera, would be a better solution if the nacreous shell structure was proven. However, that superfamily could belong also to the Euomphalina, in which the roots of the Trochina are recognisable. This is a really theoretical solution for a situation, not verified but the question, which family level taxon could be appropriate to house Discohelix and the related genera, has remained open; therefore I choose the last possibility. It is important to express, that the diagnosis of this formally not emended Discohelicidae (Discohelicoidea, Euomphalina) do not contain any constrictions on the shell structure in lack of reliable data. Genus Discohelix DVNKUR, 1847 Type species: Discohelixcalculiformis

DUNKER, 1847 Discohelix orhis (REUSS, 1852) (Figure 2) 1852: Euomphalus orbis REUSS — REUSS, p. 114, pi. 14, fig. 1. 1861 : Discohelix orbis REL'SS — STOLICZKA, p. 182, pi. 3, figs 8a-e, non 9-10. v. 1874: Discohelix orbis RF.L'SS — GEMMELLARO, G. G, p. 98. pars, v. 1911: Discohelix orbis Rl'.LSS — Gl'MMEI.I.ARO, M., p. 218. (non: Pl. 10, figs 9-12). 1912: Discohelix orbis REUSS — HAAS, p. 283, pi. 20, figs 23-24. 1924: Discohelix orbis REUSS — MAUGERI, p. 48, pl. 1, fig 26. ? 1937: Discohelix orbis RFX'SS — PCHELINCIV, p. 26, pl. 1, fig 41. 1979: Discohelix orbis (REUSS, 1852) — S/.ABÓ, p. 20, pl. 1, figs 1-3; (text)fig. 6e. 2003: Discohelix orbis (REUSS, 1852) — S/ABÓin VÖRÖS et. al., p. 64. Neotype — GBa 2008/69/32/1 /1 M a t e r i a 1 — No information was found about REUSS's (1852) syntypes, they seem to be lost, therefore a neotype is suggested here from STOLICZKA's (1861) "originals", collected from the same strata as REUSS's material. STOLICZKA's originals in the GBa, labelled as Discohelix orbis belong to four different species. STOLICZKA (1861) united Euomphalus ornatus HÖRNES, 1853 and Euomphalus orbis REUSS, 1852 (as Discohelix orbis), but provided figures to introduce both species. However, his figures about Euomphalus ornatus HÖRNES, 1853 are composed of specimens of two species: D. omata (HÖRNES, 1853) and D. pseudornata n. sp. (see them below). The holotype of Discohelix hallstattensis n. sp. was also mixed to D. orbis specimens of the "background collection". Lots of specimens (about 200 in different collections). Measurements H HI HPW D W AS AU neotype *10.2 6.6 33.8 9.8 142° GBa 2008/69/32/1/2 *9.7 6.4 *29 *8 222° -