Birds first occur in the fossil record in rocks of Upper Jurassic Age (140MYA) This earliest known bird is called Archaeopteryx, which means “ancient wing”. Archaeopteryx, was first discovered in the Solnhofen Limestone of Bavaria, Germany in 1856. Fossils of Archaeopteryx show features of both modern birds and their more generalized ancestors, theropod (meat eating) dinosaurs.
At the end of the 20th Century, new discoveries in China have brought to light a number of new species of Lower Cretaceous (125MYA) fossil birds, including Confuciusornis. These wonderfully preserved new specimens show an undisputed diversity, as well as both primitive and advanced characters. Preservation of soft parts and feathers is not uncommon at this locality, Liaoning Province, located northeast of Beijing.
By Upper Cretaceous times (90MYA) bird diversity included even secondarily flightless forms such as Hesperornis. The toothed Hesperornis was a marine bird which spent its life swimming and diving in the Western Interior Seaway of North America. Other forms, like Ichthyornis, maintained their ability to fly, while still retaining a primitive dentition. Toothed birds have not been found above the KT Boundary.
As we enter the Cenozoic era, more modern forms are recognizable. Eocene (50MYA) birds, like Presbyornis seem to be related to modern ducks, and an undescribed species to modern Kingfishers. The fossil record also produces oddities like Diatryma, a large flightless carnivore.
By Miocene times (25-10MYA) most modern bird groups are represented. Raptors, ratites and songbirds, although not abundant, still occur in the fossil record. Even fossil penguins like Paleospheniscus, look very much like their present day relatives.
There is still a strong debate between ornithologists and dinosaur paleontologists regarding the origin of birds. However, the Chinese fossil locality at Liaoning, that has produced so many fossil birds has also yielded many new skeletons of fossil theropods. The occurrence of a “downy” body covering (Sinosauropteryx, etc.) and even flight feathers (Caudipteryx and Protoarchaeopteryx) on some of the theropod skeletons offers substantial evidence of the close relationship between theropods and living birds. Additional specimens from Montana (“Bambiraptor”) and Mongolia (Oviraptor and Mononychus) have given considerable osteological evidence to support the case that theropods are not extinct.
Black Hills Institute has several fossils and fossil replicas of birds for sale. These include hesperornis and paleospheniscus skeleton.