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Ammonites were abundant marine invertebrates that went extinct roughly 65 million years ago. Their paleobiology and position in the food web are not well understood, mostly because their softer tissues are rarely preserved. Using exceptionally well-preserved fossils and synchrotron X-ray microtomography, Kruta et al. created a three-dimensional reconstruction of the jaw and radula of the ammonite Baculites. Lead author Isabelle Kruta describes the morphology of the Baculites jaw and radula, which suggest that ammonites likely fed on plankton.