Every now and then, chicken embryos sprout teeth. The developing birds don’t survive – the recessive condition is lethal – but the nascent beginnings of chicken dentition confirm something that paleontologists have known since the late 19th century. For millions of years, birds had teeth.

Yale paleontologist Othniel Charles Marsh called such birds “Odontornithes.” The term is regarded as obsolete now, but it still has a ring to it. The loon-like Hesperornis and the seabird Ichthyornis, found in the ancient chalk of a vanished Cretaceous sea and described by Marsh in 1880, provided intellectual ammunition to Thomas Henry Huxley and other naturalists who saw an undeniable connection between reptiles and birds. Huxley didn’t believe such