Odontornithes

Odontornithes is an obsolete taxonomic term proposed by American paleontologist Othniel Charles Marsh for birds possessing teeth, notably the genera Hesperornis and Ichthyornis from the Cretaceous deposits of Kansas. In 1875 he divided this "subclass" into Odontolcae, with the teeth standing in grooves, and Odontotormae, with the teeth in separate alveoles or sockets. In his 1880 work, Odontornithes: A monograph on the extinct toothed birds of North America, he added the Saururae, represented by Archaeopteryx, as a third order.

The resulting classification was paraphyletic, not accurately resolving evolutionary relationships. In the present case, the Odontornithes are not a monophyletic assembly, and the fact of their possessing teeth proves nothing but that some birds still retained these organs during the Late Cretaceous. This indicates that birds, as a group, are the descendants of toothed reptiles, to the exclusion of the Chelonia (turtles and tortoises) with which various authors had attempted to connect them. No fossil birds of later than Cretaceous age are known to have teeth.

Étienne Geoffroy Saint-Hilaire stated in 1821 that he had found a considerable number of tooth buds in the upper and lower jaws of the Rose-ringed Parakeet. Émile Blanchard felt justified in recognizing flakes of dentine. However, M. Braun and especially P. Fraisse showed later that the structures in question are of the same kind as the well-known serrated " teeth " of the bill of anserine birds. In fact the papillae observed in the embryonic birds are the soft cutaneous extensions into the surrounding horny sheath of the bill, comparable to the well-known nutritive papillae in a horse's hoof. They are easily exposed in the well-macerated under jaw of a parrot, after removal of the horny sheath. Occasionally calcification occurs in or around these papillae, as it does regularly in the egg tooth of the embryos of all birds.

The best known of the "Odontornithes" are Hesperornis regalis, standing about 3ft. high, the somewhat taller H. crassipes, and Ichthyornis dispar. Hesperornis looked somewhat similar to a loon, while Ichthyornis was quite similar to a gull or petrel. However, they were entirely distinct groups of birds and merely shared with modern birds some distant ancestry in the Early Cretaceous. The Hesperornis lineage may have derived even sooner or possibly independently from the ancestors of modern birds.