Archaeovolans repatriatus (IVPP V12444, Czerkas and Xu 2002) This Early Cretaceous bird had a controversial beginning as Archaeoraptor liaoningensis). Originally the the long stiff tail and hind limbs came from a different specimen, but phylogenetic bracketing indicates this genus had a long stiff tail. Zhou and Zhang (2002) considered the specimen another Yanornis. Here it nests between enantiornithes and the London specimen of Archaeopteryx + Hesperornis (below) and on the other branch, Eogranivora + higher birds.

A. lithographica The London specimen - BMNH 37001, is the holoytype for the genus and species. Here it nests between Archaeovolans (above) and the STM9-52 specimen (below).

Yanornis martini (Zhang & Zhou, 2001, STM9-52, Aptian, Early Cretaceous) was originally considered an ornithurine bird. Here this toothed bird with a long neck, oversized hands and small head nests basal to a toothed bird with no hands: Hesperornis. The sternum was greatly enlarged and provided with a deep keel as an anchor for powerful flight muscles, as in penguins. Tiny gastralia here are about to disappear. The sacrum is wide and not fused. The pubis extends the body posteriorly. This may be an Early Cretaceous penguin-mimic.

Hesperornis regalis (Marsh 1872a, b c) Late Cretaceous ~90 mya, 1.8m in length, was a toothed, flightless, marine loon-mimic with asymmetrical feet. Both swam with powerful hind limbs. Here Hesperornis is derived from the STM9-52 specimen (above) with origins in the Late Jurassic with the London specimen of Archaeopteryx. The premaxilla was greatly elongated. The pectoral girdle was reduced and the humerus was a vestige. Note the large patella (in blue) extending above the femur. Huge muscles were anchored to the long pelvis. The teeth had bulbous roots and were set in a groove, convergent with mosasaurs like Tylosaurus.

Czerkas SA and Xu 2002. Feathered Dinosaurs and the Origin of Flight, Czerkas SJ ed., The  Dinosaur Museum Journal 1: vi + 136 pp.

Marsh OC 1872a. Discovery of a remarkable fossil bird. American Journal of Science, Series 3, 3(13): 56-57.

Marsh OC 1872b. Preliminary description of Hesperornis regalis, with notices of four other new species of Cretaceous birds. American Journal of Science 3(17):360-365.

Marsh OC 1872c. Notice of a new and remarkable fossil bird. American Journal of Science, Series 3, 4(22): 344.

Marsh, OC 1880. Odontornithes, a Monograph on the Extinct Toothed Birds of North America. Government Printing Office, Washington DC.

Martin L 1984. A new Hesperornithid and the relationships of the Mesozoic birds. Transactions of the Kansas Academy of Science 87:141-150.

von Meyer H 1861. Archaeopteryx litographica (Vogel-Feder) und Pterodactylus von Solenhofen. Neues Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefakten-Kunde. 1861: 678–679.

Owen R 1863. On the Archaeopteryx von Meyer, with a description of the fossil remains of a long-tailed species from the lithographic stone of Solnhofen. Philosophical Transactions of the Royal Society, London 153: 33-47.

Zhang F and Zhou Z 2001. A Primitive Enantiornithine Bird and the Origin of Feathers. Science 290 (5498): 1955-1959.

wiki/Archaeovolans
wiki/Archaeopteryx
wiki/Hesperornis