Records of drill holes and repair scars on Rectithyris subdepressa (Brachiopoda) from the Maastrichtian Kallankurichchi Formation, India

Abstract

Listen

Translate article

In the post-Paleozoic communities, brachiopods are generally thought to be less attractive prey to predators than bivalves. However, recent studies have documented significant predation pressure on brachiopods throughout the Mesozoic and Cenozoic. The present study is aimed to document predation pressure on the Maastrichtian Rectithyris subdepressa from the Kallankurichchi Formation of the Cauvery Basin, India. While drilling intensity is a direct measure, repair scar frequency measures failed, non-lethal attacks. A drilling intensity of 7% and repair scar intensity of 4% is observed in the present study. These results, along with the stereotype of predatory behavior, such as the preference of size and location of the attack, indicate that both drilling and durophagous predators preyed upon Rectithyris subdepressa and the attacks are not accidental by nature. Although both predatory drill holes and repair scars could be successfully identified, specific groups could not be identified as the predators responsible for these attacks. While previous studies suggested a comparatively lower predation pressure on brachiopods than sympatric bivalves, brachiopods are the only drilled taxa in the Kallankurichchi Formation. While bivalves are the most abundant component, the large size and thicker shell of the epifaunal bivalves may explain the absence of drilling predation on the bivalves. • The Maastrichtian Kallankurichchi Formation, India, provides an excellent stratigraphic unit to test the hypothesis of reduced predation pressure on brachiopods in the Mesozoic. • Drilling and repair scar intensities indicate the presence of predation pressure on the Maastrichtian Rectithyris subdepressa. Behavioral stereotypy of predation suggests that as prey, Rectithyris subdepressa was commonly encountered by the predators. • Although bivalves are more viable prey for the predators, the sympatric bivalves in the Kallankurichchi Formation do not show evidence of drilling predation. Rectithyris subdepressa , with comparatively smaller size and thinner shell, appears to be a more cost-effective choice for the predators.