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Coelacanths are found in the fossil record as far back as 400 million years ago and even survived an earlier mass extinction 245 million years ago, yet fossils younger than 66 million years have never been found, for reasons that remain unclear. It's possible that following the Cretaceous-Tertiary extinction that wiped out the dinosaurs, coelacanths took up new habitats, like those found in the Comoros, that are not conducive to fossilization; the steep underwater slopes of these volcanic islands prevent the buildup of sediments that would normally lead to fossilization.