Post-mortem alteration of diet-related enamel surface textures through artificial biostratinomy : a tumbling experiment using mammal teeth

Abstract

In the fossil record, teeth are often all that remains of a fossil organism. Dental microwear texture analysis (DMTA) is a common proxy for diet using dental wear features at the μm-scale, enabling comparative and quantitative assessments of various feeding traits in extant and extinct species. In extinct species, original dietrelated dental wear features may be overprinted by post-mortem alteration including fluvial transport. Here we experimentally investigate the effects of mechanical alteration on diet-related 3D enamel surface texture (3DST)patterns of different mammal teeth. Post canine teeth of Equus sp., Capreolus capreolus and Otomys sp. are tumbled in sediment-water suspensions using three different grain size fractions of sand. The 3DST of the enamel surfaces are measured prior to and after each tumbling interval and characterised using ISO normed surface texture and SSFA parameters. In all species, we find several parameters to be almost unaffected by tumbling (stable parameters), while other parameters show inconsistent-directional shifts (unstable parameters). For Otomys, all three sediment grain size fractions result in abrasion of peaks and a reduction of overall surface roughness. For Equus, tumbling results in visible abrasive changes in the original wear patterns and the introduction of new wear features. Capreolus capreolus shows high variability in surface texture patterns prior to and after the experiment, hence we see ambiguous trends for changes in parameter values. However, even after 336 h of tumbling the browsing C. capreolus can still be distinguished from the grazing Equus sp. Thus, biostratinomy may potentially modify diet-related 3DST causing non-systematic bias via mechanical abrasion, which is related to sediment grain size, duration of transport and geometry of teeth. However, the original diet-related 3DST is still preserved and a more prominent characteristic in DMT than the experimentally induced diagenetic alteration.