The well-known ornithologists L. D. Martin, J. D. Steward, and K. N. Whetstone observed that Archæopteryx and other similar birds have teeth with flat-topped surfaces and large roots. Yet the teeth of theropod dinosaurs, the alleged ancestors of these birds, are protuberant like saws and have narrow roots.48
48 L. D. Martin, J. D. Stewart, K. N. Whetstone, The Auk, Vol 98, 1980, p. 86.
Larry D. Martin is an ornithologist?
I know that he’s involved in the dino-bird debate, on the "birds are not dinosaurs" side, but I thought his speciality were sabre toothed cats, so he would more likely be a mammalogist...
Anyway, the issue with the teeth difference, as far asI know, is that bird’s teeth are not much "knife-like", but rather needle-like, and so (or closer to that) have crocodilians. I don’t think that’s much of a problem because even Spinosaurus have teeth that is more like that. Also, I think that the dentitions of birds are not well known; could be that their teeth was a sublty reshaped neoteny (or pedomorphy, I never know which is which), it is, the conservation of theropod first or second dentition, which, according with one thing I saw (unfortunately, on TV) was a bit different from the definitive dentition. However, once I asked about that on a email list, and a guy said that there is not much known difference between theropod dentitions during development, and that bird dentitions are not very well known, or at least that he did not know.
(creationists, in the other hand, could say that Spinosaurus can have different teeth because it’s a "kind" in his own, not a part of theropoda or anything)
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