ICHTHYORNIS, (Yeo-Lat., from /x6Iiit, iehthys. fish --I-- /Sprit, orals, bird).
A genus of toothed birds of the Cretaeemis age, found fossil numerously in western Kansas, along with remains of Ilesperornis, Aptornis, and the like. 'These two genera represent the division Odontotortme of the toothed birds (sett Bona, eharneierized by the teeth, which the mandibles Neer(' plentifully furnished, set each in a separate alveolar socket. The various species were birds not greater than a pigeon in size, and resembling terns in general appearance and in habits. They were sea-birds of powerful flight, and the structure of their wings, legs, and carinate sternum much resembles that of modern birds. The skull, how ever. retains many reptilian features besides the teeth, such as the diminutive elongated space for the brain, the single-headed quadrate bone, and the union of the lower jaws in front by a ligament. The vertebrae. also, differ from those
of Ilesperornis and all modern birds, in being biconcave. This form of vertebra is seen in a few recent and many extinct reptiles, but is espe• (daily characteristic of fishes; tlw presence of this charaeter alone would indicate the very an tique origin of the group. These birds doubtless lived and fed as do modern gulls, seizing living tishes, and going ashore only to breed and roost at night. They were doubtless well feathered, and seem to have flourished until the end of the Cretaecous era. :Most of the fossil remains thus far obtained are in the museums of Yale Uni versity and of the University of Kansas. See lIrsemionxis; and consult the authorities there referrisl to.