Assertion: tern's beak | /r/HasProperty | filled with sharp teeth
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Source sentences:
text: They are first known to occur in the Cretaceous period, the earliest being the Hesperornithiformes, like Hesperornis regalis, a flightless loon-like seabird that could dive in a fashion similar to grebes and loons (using its feet to move underwater) but had a beak filled with sharp teeth.