The origin of drill holes
The origin of drill holes observed in tests of E. linearis from the Heterostegina Sands was discussed in detail in our previous paper see Ceranka and Zlotnik 2003 and references cited therein . The results presented there can be briefly summarised as follows 1 The penetrations observed in tests of E. linearis are typical for drillings produced by predators Carriker and Yochelson 1968 Carriker 1981 Kitchell et al. 1981 Rohr 1991 Kowalewski and Flessa 1994 and cassids are the only well-documented...
Introduction
Recent representatives of the family Cassidae are predatory gastropods that can drill in tests of echinoids to consume their internal soft tissues Hughes and Hughes 1971, 1981 Kowa-lewski and Nebelsick 2003 . Drill holes in fossil echinoids attributed to cassids have been reported from the Upper Cretaceous Rose and Cross 1993 and the Tertiary Beu et al. 1972 Gibson and Watson 1989 McNamara 1994 Ceranka and Zlotnik 2003 Kowalewski and Nebelsick 2003 . This paper deals with the patterns of...
Drilling predation intensities
The frequency of drilled tests varies notably both among the prey species and across the facies Fig. 9B Table 3 . Within a given environment, the drilling predation rates recognised for particular prey do not seem to change in any substantial matter Fig. 9A Table 3 . The only possible exceptions variations in drilling predation intensities recognised for E. pusillus and E. linearis within the fine-grained sands are most probably statistical artifacts caused by the small size of samples Fig. 9A...
Acknowledgments
Many thanks are due to Dr. Michal Kowalewski Virginia Polytechnic Institute and State University, Blacksburg and Dr. Patricia Kelley University of North Carolina at Wilmington , the journal referees who provided valuable comments, and to Dr. Anna Zylinska University of Warsaw and Dr. Michal Kowalewski who corrected the language. Special thanks are due to tukasz Ceranka who created the virtual, three dimensional models of the studied echinoids. SEM photographs have been taken by Dr. Cyprian...
Size morphology and structure of the preys test
The analysed prey species are represented by small specimens test length 1.4-6.0 mm . E. linearis is slightly smaller mean test length 2.4 mm than E. pusillus and E. pseudpusillus mean test length 2.6 and 2.7 mm respectively and the difference is statistically significant Table 1 . In all species studied, the uppermost part of the aboral side of the test is almost completely dominated by an apical disc and a large petalodium see Fig. 4O and schemes of echinoid tests on Fig 3 . Both the peristom...
Morphology and size of drill holes
The drill holes are relatively small. The maximum drill hole diameter ranges from 0.04 mm to 1.8 mm, with a mean of 0.26 mm Table 1 . The size frequency distributions of drill holes recognised for all prey species are highly right-skewed and generally unimodal, with small drill holes below 0.4 mm in diameter dominating Fig. 7 . The analysed drill holes are ca. three times smaller than those recognised by Nebelsick and Kowalewski 1999 for a Recent representative of Echinocyamus E. crispus from...
Possible taphonomic biases
Drilling predation makes the prey skeleton more prone to mechanical destruction and dissolution Roy et al. 1994 and results of this study below, but see also Zushin and Stanton 2001 . This can generate serious taphonomic biases because the intensity of drilling predation may be underestimated due to preferential destruction of the drilled skeletons. Specifically, the relative frequency of multiple drilled skeletons Fig. 15. Tests of representatives of Echinocyamus bearing multiple drill holes....