THE FOSSIL RECORD OF DRILLING PREDATION ON LINGULIDE BRACHIOPODS

The fossil record of biotic interactions between drilling predators and their shell-bearing prey has received considerable attention. However, only a few cases of drilling predation on lingulides (LINGULIDAE: BRACHIOPODA) have been documented and the macroevolutionary history of this interaction has not been addressed in the paleontological literature. Here, we explore this issue quantitatively by combining museum surveys and literature data. A total of 751 specimens of the Pliocene Glottidia inexpectans from the Atlantic Coastal Plain, were surveyed using the Florida Museum of Natural History invertebrate fossil collections. Only four drilled specimens, two valves and two conjoined shells representing four localities, were found. A number of shell fragments with distinct (half-moon) edge holes were identified. These semi-circle perforations may represent drill holes that facilitated shell breakage and induced a taphonomic bias. Additionally, an ongoing survey of published literature on the post−Paleozoic lingulides revealed additional drilled specimens, ranging in age from the Eocene to Recent. Given a potential taphonomic bias, with a preferential loss of drilled specimens, our results likely underestimate frequency of drilling in post−Paleozoic lingulides. The presence of drilled specimens in multiple time intervals and at numerous localities, non-random distribution of drill holes which tend to cluster around the prey’s body cavity (i.e., site selectivity), and the strong linear relationship between lingulide size and drillhole diameter (i.e., size selectivity) all suggest that lingulides may be an evolutionarily important prey for drilling gastropods. This interpretation is consistent with some ecological studies which indicate that drilling gastropods may have a significant impact on lingulide populations at local scales.