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)

in both faunas. All together, that means 13% of the species as the highest possible value (that contains only 5% of the specimens). Between the faunal pairs within the traditional provinces, the similarities are 2.5-5 times higher at species level than the relevant value between the two provinces (=s 13%). There is no fauna known with intermediate characters. Consequently, the "Mediterranean" faunas must have lived in an area, isolated from the stable European region. The few known African gastropods suggest a similar isolation of the "Mediterranean" area, too, there is no species in common in this pair. These two main isolations suggest an inner Tcthyan position for the areas with the faunal type, studied here. They lay on a more or less hypothetical continent (later as Intra-Tethyan Region). The isolation of the Intra-Tethyan Region is demonstrated be the characteristic evolutionary trends, resulting in a high number of genera and subgenera, missing from the surrounding palaeobiogeografic units. Twenty Bajocian genera and two subgenera did not occur in areas out of the Intratethyan Region. This number means 30% of the genera and nearly 30% of the species belongs to them. Some of the identified genera and species give new data about the evolution of higher taxa, loo. One group consists of forms, belonging to disappearing families (= archaic families sensu SZABÓ 1984): Discohelix, Pentagonodiscus, Nummotectus, Trochotomaria, Ventricarial vesicula, Mariottia, Planicollonia, Acanthostrophia. For these forms, the IntraTethyan Region served as a relict area but some of them had a last bloom before extinction (e. g. Crossostomatidae). At the same time, the first appearance of some modern higher taxa was observed: Colloniinae (Bakonyid), Rissoacea with two families (Rissoidae — Trochoturbella; Rissoinidae — Risssocerithium, Zebinostoma) and Buccinidae (Maturifusus)

. They became widespread in areas out of the Intratethyan Region only after a long time. This area can be regarded as an evolutionary center for these modern gastropods. The Intra-Tethyan Region is a so far rather hypothetic palaeogeographic unit, however, we have to suppose this area in a position like that is in the model of VÖRÖS (1977), otherwise we could not explain the great provinciality of the gastropods. The other palaeogeographic model types, connecting the elements of the "Mediterranean Province" to Europe or Africa (by shelves), do not give possibility for an adequate interpretation of the faunistic relationships. References CONTI, M. A. & FISCHER, J.

—C. (1981): Preliminary notes on the Aalenian gastropods of Case Canepine (Umbria, Italy). — in FARINACCI, A. & ELMI, S. (ed.): Rosso Ammonitico Symposium Proceedings: 137-147, Pl. 1., (Roma, 1980). CONTI, M. A. & FISCHER, J.

—C. (1983): Revisione della fauna mesogiurassica di Aque Fredde (Lago di Grada) descritta da Parona, 1894. — Boll. Mus. Civ. Storia Nat. Verona 9: 489-522, pis. 1-3. CONTI, M. A. & FISCHER, J.

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C. (1984a): La fauna a gastéropodes du Jurassique moyen de Case Canepine (Umbria, Italie). Systématique, Palécbiogéosraphie, Paléoccolosiic. — Geologica Rom. 21: 125-183, pis. 1-6. CONTI, M. A. & FISCHER, J.

—C. (1984b): Gasleropodi bajociani: Ecologia c paleobiogeoerafia. Geologica Rom. 21: 879-884. CONTI, M. A. & MONARI, S. (1987): A Middle Jurassic bivalve and gastropod fauna from Umbria (Central Italy). — Geológia Rom. 23: 175-197., pis. 1-6. HUDLESTON, W. H. (1887-1960): A Monograph of the Inferior Oolite Gastropoda. — Palaeontogr. Soc. [Monogr.], London pp. 514, pis. 44. MOORE, R. C. (ed.) 1960): Treatise on Invertebrate Paleontology. Part I, Mollusca 1. — Lawrence, Kansas. NEUMAYR, M. (1872): Ueber Jura-Provinzen. — Verhandl. kk.geol. Reichanst. 3: 54-57. SZABÓ J. (1979): Lower and Middle Jurassic gastropods from the Bakony Mountains (Hungary). Parti. Euomphalidae (Archaeosastropoda). — Annls hist.-natn. Mus. natn. hung. 71: 15-31, pis. 1-2.