Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 88. (Budapest 1996)

Dulai, A.: Taxonomic composition and palaeoecological features of the Early Badenian (Middle Miocene) bivalve fauna of Szob (Börzsöny Mts, Hungary)

this spatial division corbulids are the predominant elements of the fauna. According to LEWY & SAMTLEBEN (1979) Corbula gibba is a long- and wide-ranging species with remarkable tolerance to environmental changes. It is associated with faunas of relative lowenergy environments. FEEDING TYPE The classification and terminology of feeding types of benthic invertebrates for palaeoecological analysis is given by WALKER & BAMBACH (1974). All bivalves are heterotrophic organisms and belong to suspension feeders and deposit feeders. Suspension feeders remove food from suspension in the water mass, while deposit feeders obtain food from sediment either selectively or nonselectively. At the feeding type practically there is no difference between the two collections (Fig. 7) because deposit feeders (Nucula, Nuculana, Tellina) belong to the rare elements of the fauna, which are nearly equally represented in the two collections. The extremely low rate of deposit feeders refer to the fact that the bottom sediment was very poor in organic matter. Predominant part of the fauna is suspension feeder and the two most frequent species also belong to this group. Epifaunal elements (for example Anomia and Pectinids) acquire their food high in the water mass, while at infaunal elements (for example Anadara, Limopsis, Glycymeris, Loupes, cardiids, Venus, Lutetia. Corbula) the location of the food acquisition is low in the water mass. WATER DEPTH The preferred water depth is not known at each species, because data about depth preference are rare in the literature. It is frequent that different species of the same genus live at different depth, therefore in the case of depth range only those species were interpreted which have found in the literature. In this way 21 species in the museum collection and 12 species in the washed material were taken into consideration. In both cases the interpreted species represent approximately two-third of the fauna (66.65% and 67.24%). So in spite of the small number of interpreted species, the obtained data probably give realistic results. Some species point to a wide depth range (Fig. 8) (infralittoral - abyssal: Barbatia barbota, Striarca lactea; infralittoral - bathyal: Myrtea spinifera). Several species point to the infra- and circalittoral depth-range (Nucula nucleus, Anadara diluvii, Amusium cristatum badense, Chlamys angelonii, Chlamys scabrella, Chlamys tournali, Anomia ephippum, Lucinoma borealis, Venus multilamella, Pelecyora islandicoides, Corbula gibba). Some species point to only the infralittoral environment (Glycymeris pilosa deshayesi, Chlamys malvinae, Parvilucina dentata, Cyclocardia scalaris, Megacardita jouanneti, Lutraria oblonga, Callista italica, Pelecyora gigas). So, the examined sand probably deposited at infralittoral depth.