Response to Comment on "A Well-Preserved Archaeopteryx Specimen with Theropod Features"

^* To whom correspondence should be addressed. E-mail: Gerald.Mayr{at}senckenberg.de

Corfe and Butler (1) take issue with our statement that the data obtained from the new specimens "challenges the monophyly of Aves as currently recognized" (i.e., a clade including Archaeopteryx and modern birds but not deinonychosaurs) (2).

They recoded two characters included in our analysis, the co-ossification of metatarsals and the presence of a scapulocoracoid, referring to (3) for the presence of fused metatarsalia in Archaeopteryx. However, (3) explicitly states that the metatarsalia of Archaeopteryx were "reported to be proximally fused" in two specimens only—the now-lost third specimen and the sixth specimen. In the same study, the alleged fusion in the third specimen is then shown to be based on spurious evidence. The feet of the sixth specimen are very poorly preserved, and the original description (4) notes that in "the right foot fusion seems to be possible proximally" and in "the left foot, metatarsals II and III cannot be clearly distinguished and might be partially fused." Given that the metatarsalia are unfused in all other specimens, we do not consider this to be a convincing base for coding fused metatarsalia as present in Archaeopteryx. Likewise, the alleged fusion of scapula and coracoid is far from being certain, and these bones "appear to articulate firmly" in only three of the ten archaeopterygid specimens (3); certainly scapula and coracoid were not fused in Rahonavis (5, 6).

Corfe and Butler correctly note that the statistical support for the tree resulting from our analysis is weak, but this is also true for the competing hypothesis favored by most current researchers, that is, monophyly of a group including Archaeopteryx and pygostylians and excluding deinonychosaurs. In our study, we listed derived characters in which Microraptor agrees with Confuciusornis and other pygostylians, including the presence of ossified uncinate processes and an ulna that is much wider than the radius (2). These characters are not challenged by Corfe and Butler who, unfortunately, did not discuss the character evidence for a clade including Archaeopteryx and pygostylians to the exclusion of deinonychosaurs.

Corfe and Butler incorrectly state that we suggested "birds, or avian flight, originated twice." We do not assume that flight was gained independently more than once within theropods but consider it more likely that flight ability was lost several times independently in the clade including Archaeopteryx, deinonychosaurs, and pygostylians (7). This is a reasonable assumption irrespective of the position of Archaeopteryx, because the presence of modern-type wing feathers in the dromaeosaur Microraptor (8) alone suggests secondary loss of flight ability in the larger species of Deinonychosauria.

A clade including deinonychosaurs and more derived birds, to the exclusion of Archaeopteryx, has been discussed in detail previously (7), and there are also hypotheses that consider oviraptorosaurs, traditionally considered "non-avian" theropods, to be closer to crown group Aves than is Archaeopteryx (9).

We are not aware of any derived character shared by Archaeopteryx and Confuciusornis that is not also present in the deinoychosaur Microraptor. However, and as noted above, Microraptor shares derived characters with Confuciusornis that are absent in Archaeopteryx, and we thus do not agree with Corfe and Butler's comment that "the hypothesis of a polyphyletic Aves is no better supported by available data than that of a monophyletic Aves." One of the essentials of phylogenetic systematics, which makes it superior to other methods of phylogenetic reconstruction, is the naming of apomorphies of the clades in question. Purely statistical comparisons reduce it to just another numerical approach. Unless Corfe and Butler can present unambiguous apomorphies of a clade including Archaeopteryx and Confuciusornis, to the exclusion of deinonychosaurs, we do not believe that their argument poses a robust challenge to our hypothesis of bird ancestry.

References and Notes

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In Science Magazine

TECHNICAL COMMENTS
Comment on "A Well-Preserved Archaeopteryx Specimen with Theropod Features"

Ian J. Corfe and Richard J. Butler (1 September 2006)
Science 313 (5791), 1238b. [DOI: 10.1126/science.1130800]
 |  Abstract »  |  Full Text »  |  PDF »

REPORTS
A Well-Preserved Archaeopteryx Specimen with Theropod Features

Gerald Mayr, Burkhard Pohl, and D. Stefan Peters (2 December 2005)
Science 310 (5753), 1483. [DOI: 10.1126/science.1120331]
 |  Abstract »  |  Full Text »  |  PDF »  |  Supporting Online Material »

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