Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 79. (Budapest 1987)

Conti, M. A. ; Szabó, J.: Comparison of Bajocian gastropod faunas from the Bakony Mts. (Hungary) and Umbria (Italy)

Genus PIETTEIA COSSMANN, 1904 Subgenus Trietteia subgen. n. Type species — Pietteia (Trietteia ) trispinigera SZABÓ, 1983 (see below). Diagnosis — High spire with blunt apex, carinate slightly convex whorls and periphery. Last aperture moderately enlarged and has two protrusions above the columellar canal. Ornament of spiral threads and collabral riblets on juvenile whorls with spine on carina, only spines on later whorls and only spiral lineation on last whorl. Remarks — The three peristomial protrusions make this subgenus distinguishable from Pietteia (Pietteia

). Only two known species have this peristomial character, the type species and P. (Pietteia

) tridactyla (BUVIGNIER, 1843) occurring in the NW-European Upper Jurassic. Pietteia (Trietteia) trispinigera SZABÓ, 1983 1983 : Pietteia trispinigera SZABÓ, p. 40, Pl. Ill: figs 12-13. 1984: Pietteia apenninica CONTI et FISCHER, p. 156, fig. 13, Pl. V: fig. 23. 1987: Pietteia trispinigera SZABÓ — CONTI et MONARI, p. 192, fig. 14-15. Remarks — The specimens, coming from different localities, show a rather great variability in the transverse ornament, more exactly in the formation of the juvenile costellae. They are definite on the Bakony specimens, less expressed in Bivio Macerino and not visible on the Case Canepine specimen. The Bivio Macerino finds seem transitional between the extremities, that is why the Case Canepine "Pietteia apenninica" is regarded as junior synonym of P. (P.) trispinigera. Distribution — Somhegy, condensed Subfurcatum to Garantiana Zone and Parkinsoni Zone; Case Canepine, Humphriesianum Zone; "Bivio Macerino", ? condensed Murchisonae to Humphriesianum Zone — Humphriesianum Zone. * * * There are two other forms which may belong to the same species: Maturifusus densicostatus SZABÓ and Brachytrema purpuriniforme CONTI et FISCHER. Unfortunately, the embryonal shell of the earlier one is not known so a real comparison is not possible because the second one is represented by a very small specimen only. However, it is imaginable that the latter is a juvenile shell of Maturifusus densicostatus. PALAEOECOLOGY The faunas of Umbria and the Bakony Mountains are similar in many respects, still there are some significant differences also existing. The faunistic différences may be explained by palaeoecologic and palaeobiogeographic factors but the ratio of the two is not evident. The first comparison between the two faunas is made on the basis of the mode of life. We tried to find the main environmental circumstances favourable for the gastropods found. We collected actualistic data mainly for groups having living relatives. In case of extinct groups, we adopted results of former workers and those of unpublished facics-analysis. Hypothetical elements are used if they have been controllable and have not been in contradiction to certain elements. Table I. contains the most important information about the mode oflife of the species. However, some additional explanation seems necessary. Remarks to depth zones: 1 = = 0~50 meters; strong water movements, caused by storms, is imaginable in this interval. The archaeogastropods must have occurred in this depth zone mainly on hard ground because in soft bottom environment, the suspended sediments mean serious danger for them (possibility for infilling of the respiratory system). They might have occurred on soft bottom near the lower boundary of this interval only in dense vegetation. This colonized substrat type might have occurred in the upper part of the second depth interval, too ("1-2" in Table I.