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1 October 2007 The foot of Archaeopteryx: Response to Feduccia et al. (2007)
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Without examining the original specimen first-hand, Feduccia et al. (2007) questioned some observations in our recent description of a new skeleton of Archaeopteryx (Mayr et al. 2005, 2007). We disagree with several of their comments and believe that they gave an inaccurate account of the results of our studies in several instances.

Our statement that most specimens of the Archaeopterygidae are known from fragmentary or poorly preserved specimens was based on the fact that four of the nine specimens are known from very incomplete remains only (Maxberg, Haarlem, eighth and ninth specimens) and that only three skeletons are largely complete and have well-preserved bones (Berlin, Eichstätt, and Solnhofen specimens). Because only three of the nine specimens are well preserved, we cannot see how our statement “is easily discredited by the numerous published photographs of these specimens” (Feduccia et al. 2007:373).

Feduccia et al. (2007:373) further wrote that we reinterpreted the anatomy of the new specimen “to conform to the now largely discredited terrestrial theory for the origin of flight.” This is not correct. In fact, we did not comment at all on the lifestyle of Archaeopteryx in our 2005 study and, in the detailed description, only concluded that Archaeopteryx probably “spent most of its time on the ground” (Mayr et al. 2007:114). In the latter study, we further noted that Archaeopteryx did not have a perching foot (i.e., a foot with a large retroverted hindtoe), but nowhere did we comment on whether or not it was able to perch.

Likewise, although we believe that the hallux of archaeopterygids was spread medially, we did not claim that it was spread “at a right angle to the other claws [sic]” (Feduccia et al. 2007:374). Instead, we wrote (Mayr et al. 2005:1485) that

on both feet, the first metatarsal attaches to the medial surface of the second metatarsal…, not to its plantar surface as in extant birds with a retroverted first toe…. The shaft of the first metatarsal does not exhibit the torsion that is characteristic of birds with a fully retroverted first toe…. The proximal phalanx of the first toe further exposes its mediodorsal surface…. Because the metatarsals are visible in dorsal view, the dorsal aspect of this phalanx would not be visible if the first toe was fully reversed…. We thus conclude that the first toe of Archaeopteryx was spread medially and not permanently reversed as in extant birds.

This is possibly a linguistic problem on our side, but we consider “spread medially” and “spread medially at a right angle” to represent very different morphologies. The latter indeed is an unlikely position for a vertebrate toe.

Moreover, although we detailed the reasons for our interpretation of the hindtoe of Archaeopteryx (i.e., morphology of first metatarsal and orientation of this toe in the fossil specimen; see above), Feduccia et al. (2007:375) did not even try to refute these but simply wrote that the “hallux in Mayr et al.'s (2005) photographs opposes the other toes as it does in all other Archaeopteryx where the pertinent anatomy is preserved.” As noted in our study, a medially spread hallux is not only preserved on both feet of the new specimen but also in the Solnhofen and Berlin ones. The feet of the London and Eichstätt specimens are preserved in lateral or medial view, and the impression of a reversed first toe in these specimens is likely to be an artifact of preservation, because the medially spread toe is pressed on the level of the sedimentation layer (Mayr et al. 2005, 2007).

Feduccia et al. (2007) also seem to be unaware that a nonreversed hallux was also reported for the early Cretaceous Jeholornis (Zhou and Zhang 2006:85). Their statements also conflict with the fact that the hallux was not reversed in dromaeosaurs (Feduccia et al. 2007: lower panel of fig. 2), which, in Feduccia et al.'s (2007) phylogeny, are even closer to modern birds than Archaeopteryx. This antilogy is not even mentioned in the text.

Feduccia et al. (2007:375) correctly noted that the proximal end of the penultimate phalanx of deinonychosaurs forms an “extended ventral joint surface,” which is absent in Archaeopteryx. However, we also recognized this difference and coded the morphologies of archaeopterygids and deinonychosaurs as two different, unordered character states. The second toe of archaeopterygids lacks a hypertrophied claw and clearly served a different function than in the deinonychosaurs (Mayr et al. 2007). However, differences do not prove nonrelationship of taxa, and we still consider it possible that the proximodorsal expansion of the distal end of the first phalanx of the second toe is a shared derived character that unites archaeopterygids and deinonychosaurs.

Feduccia et al.'s (2007: fig. 3) imaginative phylogeny avoided any character conflict by omitting all dromaeosaurs other than Microraptor. By contrast, and without listing any supporting evidence, the enigmatic and very incompletely known Pedopenna daohugouensis, which was described as a maniraptoran dinosaur of uncertain affinities (Xing and Zhang 2005), is shown as sister taxon of Microraptor. If the authors had also included other dromaeosaurs in their phylogeny, such as Velociraptor or Deinonychus, it would have become all too obvious that character transformation in the lineage leading to extant birds is not as straightforward (e.g., notes above concerning the hallux).

The statement that the teeth of Microraptor are “avian style” (Feduccia et al. 2007:377) is incorrect; the teeth of Microraptor are serrated on their caudal carina and more closely resemble the teeth of the troodontid Sinovenator (Hwang et al. 2002). This statement is even more misleading, because Feduccia et al. (2007) did not mention that other dromaeosaurs, which are deliberately left out of their phylogeny (Feduccia et al. 2007: fig. 3), have typical theropod teeth.

Although Feduccia and his coauthors have until recently been among the most prominent opponents of a theropod ancestry of birds (e.g., Prum 2002), they now state that there is “little question that Archaeopteryx and, therefore, birds, are closely related to dromaeosaurids, particularly Chinese Lower Cretaceous microraptors, which we regard as a derived group of birds” (Feduccia et al. 2007: 377). They further list alleged problems with a “strict theropod ancestry” of birds (Feduccia et al. 2007: 377), but conclude with the statement that the “great challenge for archosaurian paleontology is to tease out the exact avian clade from early theropods with superficially similar structure” (Feduccia et al. 2007: 379). Although we agree with Feduccia et al. (2007) that the interrelationships between Archaeopteryx, deinonychosaurs, and more advanced birds are far from being understood fully (Mayr et al. 2005), we do not believe that such confusing statements shed new light on the ancestry of birds.

Literature Cited

1.

A. Feduccia, L. D. Martin, and S. Tarsitano . 2007. Archaeopteryx 2007: Quo vadis? Auk 124:373–380. Google Scholar

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S. H. Hwang, M. A. Norell, and K. Gao . 2002. New specimens of Microraptor zhaoianus (Theropoda: Dromaeosauridae) from northeastern China. American Museum Novitates 3381:1–44. Google Scholar

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G. Mayr, B. Pohl, S. Hartman, and D. S. Peters . 2007. The tenth skeletal specimen of Archaeopteryx. Zoological Journal of the Linnean Society 149:97–116. Google Scholar

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G. Mayr, B. Pohl, and D. S. Peters . 2005. A well-preserved Archaeopteryx specimen with theropod features. Science 310:1483–1486. Google Scholar

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R. Prum 2002. Why ornithologists should care about the theropod origin of birds. Auk 119:1–17. Google Scholar

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X. Xing and F-C. Zhang . 2005. A new maniraptoran dinosaur from China with long feathers on the metatarsus. Naturwissenschaften 92:173–177. Google Scholar

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Z-H. Zhou and F-C. Zhang . 2006. Mesozoic birds of China—A synoptic review. Vertebrata PalAsiatica 44:74–98. Google Scholar

Appendices

Gerald Mayr and D. Stefan Peters "The foot of Archaeopteryx: Response to Feduccia et al. (2007)," The Auk 124(4), 1450-1452, (1 October 2007). https://doi.org/10.1642/0004-8038(2007)124[1450:TFOART]2.0.CO;2
Received: 1 June 2007; Accepted: 1 July 2007; Published: 1 October 2007
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