I have been saying it for years: The transition from dinosaur (figuratively speaking) to chicken was gradual, but at some time we stopped calling it a dinosaur and started calling it a chicken. Or would have if we had been there. The chicken therefore emerged from an egg laid by a dinosaur. Hence, the egg came first. See Robert Krulwich’s article on NPR and the splendid video he links to if you do not believe me.
Acknowledgement. Thanks to Dave Carlson, who asks, “Which came first, the panda or the panda’s thumb?” for the link.