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Are shark teeth proxies for functional traits? A framework to infer ecology from the fossil record
Journal of Fish Biology
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Modern sharks have an evolutionary history of at least 250 million years and are known to play key roles in marine systems, from controlling prey populations, to connecting habitats across oceans. These ecological roles can be quantified based on their functional traits, which are typically morpholo...
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Modern sharks have an evolutionary history of at least 250 million years and are known to play key roles in marine systems, from controlling prey populations, to connecting habitats across oceans. These ecological roles can be quantified based on their functional traits, which are typically morphological (e.g., body size) or behavioural (e.g., feeding and diet). However, our understanding of such roles of extinct sharks is limited by the inherent incompleteness of their fossil record, which consists mainly of isolated teeth. As such, establishing links between tooth morphology and ecological traits in living sharks could provide a useful framework to infer sharks’ ecology from the fossil record. Here, based on extant sharks from which morphological and behavioural characteristics are known, we assess the extent to which isolated teeth can serve as proxies for functional traits. To do so, we first review the scientific literature on extant species to evaluate the use of shark dental characters as proxies for ecology to then perform validation analyses based on an independent dataset collected from museum collections. Our results reveal that 12 dental characters have been used in the shark literature as proxies for three functional traits: body size, prey preference and feeding mechanism. From all dental characters identified, tooth size and cutting edge are the most widely used. Validation analyses suggest that seven dental characters – crown height, crown width, cutting edge, lateral cusplets, curvature, longitudinal outline and cross-section outline – are the best proxies for the three functional traits. Specifically, tooth size (crown height and width) was found to be a reliable proxy of all three traits; the presence of serrations on the cutting edge was one of the best proxies for prey preference; and tooth shape (longitudinal outline) and the presence of lateral cusplets were among the best indicators of feeding mechanism. Taken together, our results suggest that in the absence of directly measurable traits in the fossil record, these seven dental characters (and different combinations of them) can be used to quantify the ecological roles of extinct sharks. This information has the potential of providing key insights into how shark functional diversity has changed through time, including their ecological responses to extinction events.
Body size; dental characters; ecological role; feeding mechanism; prey preference; tooth morphology
Faculty of Science and Engineering
Swansea University. Fisheries Society of the British Isles - PhD studentship. University of Florida - International Travel Grant. Swiss National Science Foundation - PRIMA 185798