A BORING ANALYSIS: COMPARING RECENT AND FOSSIL DRILLING PREDATION ON THE CLYPEASTEROID ECHINOID ECHINOCYAMUS

Drilling predation is known to occur in recent marine environments with cassid gastropods attacking both regular and irregular echinoids leaving a characteristic drillhole as a predation mark. The investigation of predatory drilling patterns can supply information concerning hunting behaviour and intensity by the analyses of prey selection, size and site selectivity as well as drilling frequencies in both recent and fossil populations. The minute clypeasteroid echinoid Echinocyamus is used in this analysis since it is easy to collect, abundant in a wide variety of habitats, occurs in Recent as well as in Fossil records and can be well preserved.

In this study, numerous Echinocyamus pusillus tests from the Mediterranean Sea (Giglio Island) are analysed with respect to drilling frequencies, site- and size selectivity as well as for drillhole morphology. The results are compared to fossil Echinocyamus from the Oligocene of northern Germany (Doberg). Drillhole morphologies show that the holes are highly affected by microstructures of the test including tuberculation and ambulacral pores. The drillholes also show a concave wall profile which seems to correlated to stereom density of the echinoid test. The analyses show similar drilling intensities in the data sets from the Mediterranean Sea and Doberg. The analysis of size selectivity indicates that predators do not select their prey for specific size classes. There is also a high site selectivity for drilling sites for the aboral side of the test, especially in or near the petalodium.