Hesperornis and Ichthyornis, birds with teeth
A flightless diving bird and a tern-like flier, both with jaws full of teeth, swim the American seaway.
- When
- —
- Duration
- 12 million years
- Known to
- ± 3 million years
- Era
- Cretaceous, Mesozoic
Hesperornis is a large flightless foot-propelled diver, so specialised for swimming that it could barely move on land; Ichthyornis is a strong-flying seabird about the size of a pigeon. Both retain teeth in their jaws while otherwise looking thoroughly modern, and when Marsh described them in the 1870s they were seized on as vertebrate transitional forms, cited by Darwin's defenders and attacked in Congress as a waste of public money. They are the clearest evidence that the beak arrived in stages, and that toothed birds persisted right up to the end of the Cretaceous.