Paleornithology also known as Avian Paleontology is the scientific study of bird evolution and fossil birds. It is a mix of ornithology and paleontology. Paleornithology began with the discovery of Archaeopteryx. The reptilian relationship of birds and their ancestors, the theropod dinosaurs, are important aspects of paleornithological research. Other areas of interest to paleornithologists are the early sea-birds Ichthyornis , Hesperornis, and others. Notable paleornithologists are Storrs L. Olson, Alexander Wetmore, Alan Feduccia, Philip Ashmole, Pierce Brodkorb, Trevor H. Worthy, Zhou Zhonghe, Bradley C. Livezey and David Steadman.