Ornithurae Ornithurae Ornithurae (meaning "bird tails" in Greek) is a natural group which includes the common ancestor of "Ichthyornis", "Hesperornis", and all modern birds as well as all other descendants of that common ancestor. Ernst Haeckel coined the name in 1866 and included in the group all "true birds" with the "characteristic tail morphology of all extant birds" (translation by Jacques Gauthier). This distinguishes the group from "Archaeopteryx", which Haeckel placed in another new group called Sauriurae. Said simply, modern birds have short, fused pygostyle tails, while "Archaeopteryx" retained the long tail characteristic of non-avian theropod dinosaurs. Gauthier converted Ornithurae into
Dinosaur tooth data that has been collected through dinosaur dental histological studies are typically unavailable through other means and has provided us with a more in-depth understanding on their biology. One of the most significant findings is that despite differences in their appearance, dinosaur teeth are essentially composed of the same dental tissues found in modern mammals, crocodilians and other amniotes, suggesting that these tissues first evolved in a common ancestor and has been retained ever since. Another finding is that the lines of von Ebner can be counted similar to tree rings to determine the age of a tooth. Furthermore, as