Szabó János szerk.: Fragmenta Mineralogica Et Palaentologica 24-25. 2007. (Budapest, 2007)
1.2 mm for juveniles and 2.4—2.8 mm for mature specimens (they used width instead of length measurements). Assuming the same growth rate in Middle Miocene, there are 25% H 20 15 105 "i —I —I —r 1 2 3 length (mm) no newly settled larvae in the Bánd sample and the number of juveniles is also very low. Most of the specimens probably belong to young adult and mature brachiopods. 25%20 15 105 1 i 2 3 length (mm) Figure 7 — Size-frequency histograms of Argyrotheca Figure 8 — Size-frequency histograms of Argyrotheca cuneata (Risso, 1826), Bánd. cordata (Risso, 1826), Bánd. Epizoans on micromorphic brachiopods Encrusters may provide information about life orientation of the host and may have also some sedimentological implications (CUFFEY et al. 1995). Brachiopods can offer hard substrate for epizoans, but the amount of encrusters is very variable on fossil and Recent forms. About 10% of the Eocene brachiopods from Antarctica were encrusted by epifaunal organisms (bryozoans, foraminifers, serpulid polychaetes, cirripeds, octocorals; BlTNER 1996). However, 80% of Recent Neocrania huttoni carried epibionts in New Zealand (LEE 1987). ( )nlv a very small part of the studied Hungarian specimens (427) were encrusted (Figure 9). None of the brachiopods carried more than one specimen of encrusters. No encrustation is observed on the three M. detruncata specimens. Only one out of 147 specimens (0.7%) of A. cuneata shows the possible remain of a serpulid. The serpulid tube already disappeared, but the meandering attachment place can be seen at the middle part of the dorsal valve (Figure 9: 6). Two out of 275 specimens (0.7%) of A. cordata earn* encrustation (one bryozoan and one serpulid). The bryozoan larva settled on the ventral valve near to the anterior margin (Figure 9: 1-3). Unfortunately, the studied bryozoan is very badly-preserved, but shows some similarities to Annectocyma? (MoiSSETTE pers. com.). Annectocyma major is generally common in Hungarian Badenian Bryozoa fauna (MOISSETTE et al. 2006). The serpulid polychaete tube is also situated on the ventral valve, at the most terminal part of the anterior margin (Figure 9: 4—5). Taking into consideration the life position of megathyridids, the ventral valve and mainly the terminal part of the ventral valve is situated at the highest point. These brachiopods are sometimes very densely packed, and in these cases only the abc we mentioned parts of the shells are available as solid substrate for the settlement of different larvae. It suggests that both the Bryozoa and the serpulid Polychaeta probably encrusted the ventral valves of A. cordata during the life of these brachiopods. As the serpulid attached very near to the anterior commissure, it may benefit from the feeding currents of the brachiopod. Similar situations were reported on the Palaeozoic Mucrospirifer (SCHUMANN 1967), on the Eocene Paraplicirhjnchia (BlTNER 1996), and on Cenozoic and Recent Tegulorhynchia (LEE 1980). The possible serpulid on the middle part of dorsal valve of A. cuneata probably settled after the death of the brachiopod. Generally the larger sized brachiopods show traces of epibionts. The encrustation of micromorphic brachiopods is not well-represented in palaeontological Hterature. RUDWICK (1962) observed epifauna associated usually with larger brachiopod shells. LEE (1987) found that most of the epibiont-free valves were juveniles, i. e. less than 8 mm at Recent Neocrania huttoni. BlTNER (1996) noted that in the case of Eocene Terebratu/ina buckmanni, absence of epibionts might be the result of its small size. She also mentioned another possible explanation: some Recent Terebratulina are very often covered by encrusting sponges leaving no traces in the fossil record (SURLYK 1972). Using of micromorphic brachiopods as solid
