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in Bazzi, Campione, ... et Ahlberg, 2021. |
Highlights:
• Shark tooth morphologies track changing habitats and resource availability
• Tooth shape correlates with diet in extant shark species
• Declines in lamniform disparity can be linked with dietary “specialization”
• Modern lamniforms are more disparate than coeval carcharhiniforms
Summary
Sharks are iconic predators in today’s oceans, yet their modern diversity has ancient origins. In particular, present hypotheses suggest that a combination of mass extinction, global climate change, and competition has regulated the community structure of dominant mackerel (Lamniformes) and ground (Carcharhiniformes) sharks over the last 66 million years. However, while these scenarios advocate an interplay of major abiotic and biotic events, the precise drivers remain obscure. Here, we focus on the role of feeding ecology using a geometric morphometric analysis of 3,837 fossil and extant shark teeth. Our results reveal that morphological segregation rather than competition has characterized lamniform and carcharhiniform evolution. Moreover, although lamniforms suffered a long-term disparity decline potentially linked to dietary “specialization,” their recent disparity rivals that of “generalist” carcharhiniforms. We further confirm that low eustatic sea levels impacted lamniform disparity across the end-Cretaceous mass extinction. Adaptations to changing prey availability and the proliferation of coral reef habitats during the Paleogene also likely facilitated carcharhiniform dispersals and cladogenesis, underpinning their current taxonomic dominance. Ultimately, we posit that trophic partitioning and resource utilization shaped past shark ecology and represent critical determinants for their future species survivorship.
Keywords: Lamniformes, Carcharhiniformes, geometric morphometrics, dental disparity, feeding ecology, environmental change, ecomorphology
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| Lamniformes and Carcharhiniformes across the last 83 million years. Illustration: José Vitor Silva |
Mohamad Bazzi, Nicolás E. Campione, Benjamin P. Kear, Catalina Pimiento and Per E. Ahlberg. 2021. Feeding Ecology has shaped the Evolution of Modern Sharks. Current Biology. In Press. DOI: 10.1016/j.cub.2021.09.028
In brief: Bazzi et al. analyze the evolution of lamniform and carcharhiniform shark over the last 83 Ma. These closely related clades are shown to have undergone marked morphological segregation, with a combination of habitat change, prey availability, and feeding strategies influencing their community composition, diversity, and ecology over time.
