Bird, Dinosaur Link

Abstract

Ann Gibbons's Research News article “Missing link ties birds, dinosaurs” about the discovery of the unusual Cretaceous bird Rahonavis (nee Rahona) (20 Mar., [p. 1851][1]) includes commentary from two scientists who doubt that the forelimbs and hindlimbs belong to a single animal. One of the authors of the original report (20 Mar., [p. 1915][2]), Catherine A. Forster, is quoted in response that a source from two different animals cannot be ruled out, although “she contends that the hind limbs are clearly bird legs.” In fact, the study itself shows a stronger test of this hypothesis (Forster et al.'s note 22, [p. 1915][2]) that was not reflected in the News article. Phylogenetic analyses were run twice, once including the questioned forelimb material, which was found “next to or touching the hind portion of the skeleton,” and once without it. In both cases the phylogenetic position of Rahonavis was the same, clustering with Unenlagia plus Archaeopteryx and other birds. This shows clearly that the fore and hind limbs belong to the same animal, unless they represent two different kinds of animals with exactly the same evolutionary relationships to other groups (which would amount to nearly the same thing). Critics of the dinosaurian ancestry of birds are quoted as characterizing Rahonavis as “a little dinosaur hindquarter, with a bird's forelimbs,” or as “another dinosaur trying to hit it big as a bird.” The kinds of analysis that Forster et al . carried out indicate that these critics are closer to the mark than they would like to be, because the overwhelming evidence indicates that birds did indeed evolve from dinosaurs ([2][3]). As evolutionary theory would predict, the most basal birds show a mosaic of retained theropod features and new avian characters. 1. 1. K. Padian, 2. L. Chiappe , Biol. Rev. 73, 1 (1998). [OpenUrl][4][CrossRef][5][GeoRef][6] 2. [↵][7]1. L. Dingus, 2. T. Rowe , The Mistaken Extinction (Prentice-Hall, New York, 1997). [1]: /lookup/doi/10.1126/science.279.5358.1851 [2]: /lookup/doi/10.1126/science.279.5358.1915 [3]: #ref-2 [4]: {openurl}?query=rft.jtitle%253DBiological%2BReviews%2B%2528Cambridge%253B%2BPrint%2529%26rft.stitle%253DBiological%2BReviews%2B%2528Cambridge%253B%2BPrint%2529%26rft.volume%253D73%26rft.issue%253D1%26rft.spage%253D1%26rft.epage%253D42%26rft.atitle%253DThe%2Borigin%2Band%2Bearly%2Bevolution%2Bof%2Bbirds%26rft_id%253Dinfo%253Adoi%252F10.1017%252FS0006323197005100%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [5]: /lookup/external-ref?access_num=10.1017/S0006323197005100&link_type=DOI [6]: /lookup/external-ref?access_num=1998038706&link_type=GEOREF [7]: #xref-ref-2-1 View reference 2 in text