Ornithoprion

Ornithoprion is an extinct genus of cartilaginous fish. The only species, O. hertwigi, lived during the Moscovian stage of the Pennsylvanian, between 315.2 and 307 million years ago, and is preserved in black shales from what is now the Midwestern United States. The study of Ornithoprion was performed primarily via x-ray imaging, and at the time of its discovery it represented one of the best known Paleozoic holocephalans. The classification of the genus has been the subject of debate due to its unique anatomy, but it is now placed in the order Eugeneodontiformes and the family Caseodontidae. Ornithoprion's genus name, which may be translated as 'bird saw', was inspired by the animal's vaguely bird-like skull and the saw-like appearance of the teeth in the lower jaw, while the species name honors Oscar Hertwig.

Ornithoprion is unique among known eugeneodonts for the extremely long mandibular rostrum extending from the lower jaw, which was protected by a beak of fused bony scales and which the function of in life is not known. It inhabited shallow marine environments and coexisted with a variety of other cartilaginous fishes. The structure of Ornithoprion's teeth suggests that it was a durophage which hunted shelled marine invertebrates, and bite marks and damage to its fossils indicate it was fed on by other carnivores. Ornithoprion was small relative to other members of its order, with a cranium length of up to 10 centimetres (3.9 in) and an estimated body length of up to approximately 91 centimetres (36 in).