Despite the occupation by reptiles of almost every ecological niche during the Mesozoic Era, there were no large planktivorous marine reptiles, the niche filled today by baleen whales.
Recent discoveries in museum drawers may hold the answer to this gap in Mesozoic reptile ecology. Fossils that had lain unstudied or incorrectly identified have been newly identified as suspension-feeding pachycormids, a group of giant bony fish.
These fish were previously thought to have been a short-lived group, limited to the Jurassic Period. Mesozoic marine reptiles may have been excluded from the large-bodied, suspension-feeding trophic niche by these supersized fish.
The pachycormids were extinct by the end of the Cretaceous Period, opening up the planktivorous niche to a new group--the whales.
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