Szabó János szerk.: Fragmenta Mineralogica Et Palaentologica 24-25. 2007. (Budapest, 2007)

FRAGMENTA PALAEONTOLOGICA HUNGARICA 24-25, BUDAPEST, 2007 Badenian (Middle Miocene) micromorphic brachiopods from Bánd and Devecser (Bakony Mountains, Hungary) by Alfréd DULAI Abstract — The described brachiopod assemblage (427 specimens from the Lower Badenian shallow water deposits of the Bakony Mts) comprises 3 micromorphic species belonging to two genera of Megathyrididae. Argyrotheca cordata and A. cuneata are relatively common members of the coral-bearing, diverse fauna at Bánd. The very limited Devecser material yielded isolated but well-preserved A. cordata and Megathiris detruncata valves. All the three species are widespread in the Miocene of the Central Paratethys, as well as in the Recent seas. The Bánd assemblage is more or less autochthonous while the Devecser brachiopods suggest only short transportation. The two Argyrotheca species show bell-shaped size-frequency distribution indicating low juvenile mortality. Protected, cryptic environments among coral branches and under boulders resulted in the unimodal, bell-shaped size distribution, indicating a stable community. Epifaunal encrusters (Bryozoa, serpulid Polvchaetes) are recorded for the first time on micromorphic brachiopods in the Central Paratethys. The situation of epibionts suggests that they encrusted the ventral valves during the life of brachiopods. The serpulid probably benefits from the feeding currents of the brachiopod. Few brachiopod specimens (3.5%) show drill holes of predatory* gastropods. No taxon selectivity can be observed, but A. cuneata shows valve and site selectivity. Keywords — Brachiopoda, Argyrotheca, Megathiris, Middle Miocene, Badenian, Hungary, Central Paratethys, size-frequency distribution, drilling prédation, encrustation. DULAI, A.: Badenian (Middle Miocene) micromorphic brachiopods from Bánd and Devecser (Bakony Mountains, Hungary). — Fragmenta Palaeontologica Hungarica, 24—25: 1-13. Introduction Brachiopods were important in the Palaeozoic and partly in the Mesozoic marine assemblages, but they are generally rare in the Cenozoic deposits. The Badenian (Middle Miocene) marine fauna is very abundant and diverse in Hungary*, but brachiopods are scarce elements of these fossil assemblages. Hungarian Miocene brachiopods were mainly mentioned in faunal lists. Some new species were described by MATYASOVSZKY (1880) and MAjER (1915). MEZNERICS (1943) summarized the Hungarian Tertiary brachiopod fauna in a small monograph and described 42 species (6 new) from 11 Eocene, 3 Oligocène and 31 Miocene localities. Recently BlTNLR & DULAI (2004) revised the Miocene brachiopods in the palaeontological collections of the Hungarian Natural History* Museum, Budapest. Altogether 16 species were recognized in this material from which Argyrotheca cuneata was reported for the first time from the Miocene of Hungary. Some earlier authors over-splitted the Paratethyan and Mediterranean Miocene brachiopod faunas and mentioned many species, subspecies and varieras (e. g. SACCO 1902; FRIEDBERG 1921; MEZNERICS 1943). The Badenian (Middle Miocene) fauna of the Central Paratethys recently was critically evaluated on the basis of the very rich material of the Roztocze Hills in Poland (nearly 14000 specimens) by BlTNHR (1990). She resolved several taxonomical problems and identified some of the Paratethyan species with the Recent Mediterranean fauna. The rich Polish material permitted to establish the range of variability for several species, including also the three species discussed here. 16° 18° 20° 22° 16° / 18° 20° 22° Figure 1 — Sketch map showing the location of Bánd and Devecser outcrops.