Szabó János szerk.: Fragmenta Mineralogica Et Palaentologica 24-25. 2007. (Budapest, 2007)
10 DUT where the dorsal valve was more frequentiy drilled. (However, it has to be mentioned that the Hungarian results are based only on 15 drilled specimens, while the Polish data are based on 514 drilled brachiopods). At the same time, similarly to the Polish results, some differences can be seen in valve selectivity"- at the two separated Argyrotheca species. Valve selectivity 7 is lower at A. cordata because 5 drill holes were found on ventral and 3 holes on dorsal valves (50% and 30%») (two holes are at the margins). More significant valve selectivity seems to be at A. cuneata where 4 drill holes were found on the ventral valve and only one on the dorsal valve (80%—20%, but based only on five specimens). Ventral valve selectivity 7 can be explained assuming that predator) 7 gastropods attack the living brachiopod specimens, because the ventral valve is more accessible for predators in life position. A. cordata shows random drill hole distribution on both valves (Figure 12), but the drill holes are concentrated on a small area on the ventral valve of A. cuneata (Figure 11). It may suggest site selectivity in the predators of the latter species. As all of the smdied Argyrotheca specimens are ver) 7 small, and their size-interval is rather narrow T \i, A. (most of the specimens are between 1.5 and 3 mm in length), it is not worth comparing the size of drilled and undrilled brachiopods. Anyway, no statistically significant size differences were found between drilled and undrilled specimens by BAUMILLER & BlTNER (2004) on a much larger database. Two of the drill holes are unfinished (e.g. Figure 10: 5), therefore the prédation was unsuccessful. No multiple holes occurred on the smdied brachiopods. Axes of the holes are perpendicular to the shell surface. These features, as well as the outline and size of the drill holes refer to predator activity 7 , not substrate penetration (KELLEY & HANSEN 2003). The drill holes are both cylindrical and conical in cross section, but conical holes are much more common. The former ones refer to muricid gastropods, while the latter ones can be attributed to naticid gastropods. Both muricids and naticids were diverse and abundant at the studied Bánd locality (e.g. Murex cf. aquitanicus, Murex subtoruiarius, Muricopsis cristatus, Polinices redempta dertoconvexa, Polynices olla, Natica tigrina hörnest; KÓKAY 1966), therefore it is impossible to identify the predator species. Figure 10 — Traces of drilling prédation on micromorphic brachiopod valves by predatory gastropods, Bánd. — 1: Ventral view of a drilled Argyrotheca cordata (L: 2,7 mm; W: 2.6 mm), xl9; 2: Ventral view of a drilled Argyrotheca cordata (L: 2.4 mm; W: 2.5 mm), x20; 3: Detail of Figure 10: 2, showing the drillhole, x48; 4: Dorsal view of a drilled Argyrotheca cordata (L: 2.6 mm; W: 2.7 mm), x20; 5: Ventral view of a drilled Aigyrotheca cordata, showing an unsuccessful drilling (L: 2.4 mm; W: 2.2 mm), x23; 6: Anterior view of a drilled Atgyrotheca cuneata (L: 2.3; W: 2.5 mm), x22; 7: Ventral view of a drilled Argyrotheca cuneata (L: 2.2 mm; W: 3.1 mm), xl8; 8: Detail of Figure 10: 7, showing the drillhole, x48.
