One very simplified cladogram for birds is shown below:
Archaeopteryx and some other extinct groups are not included in the crown group. They fall outside the Neoaves clade, as they diverged earlier. They are not part of the clade which resulted in modern birds.
Stem group [change]
The stem group of birds would be all the earlier Aves minus the crown group.
- Budd, G.E.; Jensen, S. (2000), "A critical reappraisal of the fossil record of the bilaterian phyla", Biological Reviews 75 (2): 253–295, doi:10.1017/S000632310000548X, PMID 10881389, http://journals.cambridge.org/production/action/cjoGetFulltext?fulltextid=624
- Chiappe, Luis M. (2007), Glorified dinosaurs: the origin and early evolution of birds, Sydney: University of New South Wales Press, ISBN 978-0-86840-413-4
- UCMP Glossary: Phylogenetics, University of California Museum of Paleontology, http://www.ucmp.berkeley.edu/glossary/glossary_1.html, retrieved 2010-12-04