A Critique of the Theropod Ancestry of Birds (Sidebar 1)

In the 1970's, John Ostrom of Yale University described the anatomy of the (bi-pedal, carnivorous) dinosaur Deinonychus and emphasized the similarities between theropods and birds. Ostrom was not the first to suggest the evolutionary descent of birds from dinosaurs, but his work has been a primary catalyst in the current belief that birds are the direct descendants of dinosaurs. Many paleontologists (if not most) believe that birds actually are living dinosaurs (calling them "avian theropods"). Some of the similarities between birds (especially Archaeopteryx) and theropod dinosaurs are listed below:

1. Hollow bones
2. Clavicle and furcula (some theropods)
3. Half-moon shaped wrist bone
4. Shape and orientation of the pubic bone
5. Three fingers
6. Stiff tail
7. Other similarities of the skull

Alan Feduccia, an ornithologist from the University of North Carolina, disagrees with the supposed "fact" that birds are living dinosaurs. Although Feduccia concurs that birds did evolve from a reptilian common ancestor, he does not believe that ancestor was a dinosaur. He points out four main problems with the dinosaur-bird link:

1. Archaeopteryx appears before theropod dinosaurs in the fossil record. Archaeopteryx is believed to be 150 million years old, but the theropod dinosaurs, that are thought to be the ancestors of birds, are 65 to 110 million years old. The common reply to this objection is that the fossil records of both birds and dinosaurs are just too fragmentary.
2. The second problem with the dinosaur-bird link is that dinosaurs are not good predecessors for flight. Feduccia, as quoted in The Chronicle of Higher Education says, "It is biophysically impossible to imagine how flight could evolve from large, earth-bound creatures with heavy balancing tails and already foreshortened limbs" (McDonald, 1996).
3. A third problem is the anatomical differences between therapods and birds. For example, many fossil bird specimen had teeth in their bills, and these teeth have been long counted as evidence of reptilian descent. The teeth of the fossil birds are not similar to dinosaur teeth though. Most bird teeth are "peg-like" and have no serration. Also, birds have reversed toes for perching, but no dinosaur has been found with a reversed toe. Dinosaurs have reptilian jaw joints that no bird has ever been known to have.
4. A fourth problem is that the anatomy of the bird "hand" is fundamentally different from that of the theropod hand. Although both types of hands posses three fingers, theropods have fingers I, II, and III (thumb, index and middle) but birds have fingers II, III, and IV (index, middle, and ring) (Burke and Feduccia, 1997). The identification of the retained fingers was determined by analysis of the wrist bones during embryonic development of chicks and other birds and of several types of reptiles.

John Ruben, a zoologist from Oregon State University who studies the physiology of dinosaurs from their remains, has concluded that the lung structures of theropods and birds are different enough to be a problem for any dinosaur-avian lineage (Ruben, et al., 1997). The theropod dinosaurs seem to have had a diaphragm (like crocodiles do), but birds do not have diaphragms, and there is no evidence that they ever did have them. Rather, birds have a unique respiratory system. Ruben et al. (1997) claim that the differences in the theropod and bird respiratory systems "pose fundamental problems" for a direct relationship.

Another common claim that we hear is that fossils have been found in China of dinosaurs that had feathers. There are three examples: Sinosauropteryx, Protarchaeopteryx, and Caudipteryx (Qiang, et al., 1998) (Gibbons, 1996). These animals had shorter arms than most birds do so they apparently could not fly at all. Larry Martin, another evolutionist who doubts the dinosaur ancestry of birds, was among the group of American ornithologists and paleontologists that went to China to see the Sinosauropteryx fossils. The group returned agreeing that the dinosaur (which is similar to Compsagnathus) did not posses feathers, but rather had some sort of dermal filaments. Martin believed the filaments may have been similar to the fringe on the spine of iguanas (Gibbons, 1996). Commenting on Protarchaeopteryx and Caudipteryx, Martin and Feduccia have both said that they were most likely non-flying birds, and not reptiles at all (Gibbons, 1998). Martin said that both the Protarchaeopteryx and the Caudipteryx had features that made them appear to be even more avian than Archaeopteryx—for example, shorter tails and ossified sternums (Gibbons, 1998).

In summary, there are serious problems with the belief that birds are the living branch of the extinct dinosaurs. The evolutionary dates assigned to theropods and to Archaeopteryx are difficult to make compatible. The anatomical and physiological differences between theropods and birds are difficult to overlook. The differing bone patterns in the hands are impossible to ignore. Further, there is still no undisputed example of the origin of feathers. While there are similarities among some theropods and some fossil and living birds, Ruben believes that the similarities can be explained by a similar function. They both could run well, so they both had similar anatomy for the same task (Murrell, 1997). Creationists agree. God made birds and dinosaurs as distinctly unique kinds of animals, and the evidence supports this.

References:
Burke, A and Feduccia, A. 1997. "Developmental Patterns and the Identification of Homologies in the Avian Hand" in Science 278 p.666-668.

Gibbons, A. 1996. "New Feathered Fossil brings Dinosaurs and Birds Closer" in Science 274:720-721.

Gibbons, A. 1998. "Dinosaur Fossils, in Fine Feather, Show Link to Birds" in Science 280:2051.

McDonald, Kim. October 25, 1996. "A Dispute over the Evolution of Birds" in The Chronicle of Higher Education p. A15.

Murrell, D. 1997. "A Bone to Pick" in The Chapel Hill Herald vol.9(348):1.

Qiang, J.; Currie, P.J.; Norell, M.; and Shu-An, J. 1998. "Two Feathered Dinosaurs from Northeastern China" in Nature 393:753-761.

Ruben, J.A.; Jones, T.D.; Geist, N.R.; and Hillenius, W.J. 1997. "Lung structure and Ventilation in Theropod Dinosaurs and Early Birds" in Science 278:1267-1270.

Copyright © 1999 Institute for Creation Research
All Rights Reserved