[[Fugle]] er direkte efterkommere af [[theropoder]]ne og således en undergruppe af Saurischia i [[evolution]]en.<ref name="padian2004">{{cite book|author=Padian, K.|year=2004|title=The Dinosauria|url=https://archive.org/details/dinosauriandedit00weis|pages=[https://archive.org/details/dinosauriandedit00weis/page/210 210]–231|chapter=Basal Avialae|edition=Second|location=Berkeley|publisher=University of California Press|editor=Weishampel, David B.|isbn=0-520-24209-2|editor2=Dodson, Pete]|editor3=Osmólska, Halszka}}</ref> En analyse, gennemført i 2017 har imidlertid sået tvivl om klassifikationen, idet theropoder her anses for at tilhøre ordenen [[Ornithoscelida]].<ref>Baron, Matthew G.; Norman, David B.; Barrett, Paul M.. ”[http://www.nature.com/nature/journal/v543/n7646/full/nature21700.html A new hypothesis of dinosaur relationships and early dinosaur evolution]” (på en). ''Nature'' 543 (7646): sid. 501–506. [[Digital object identifier|doi]]:[[doi:10.1038/nature21700|10.1038/nature21700]]. [[International Standard Serial Number|ISSN]] [http://worldcat.org/issn/0028-0836 0028-0836].</ref>
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