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My contribution (which I am sure "Discover" will undoubtedly print in their next edition) following on from Norell's insipid warm-over of his half-baked ideas, is as follows: Czerkas is not the only person who believes Norell's use of cladistics is “one of the biggest mistakes ever made in paleontology”. One assymmetrical feather doesn't prove powered flight, but a set of all-round bodily attributes ideally suited to flight including perfect and very large thrust-producing primary feathers as seen on some dromaeosaurs is best explained by an ability to fly. Perhaps the world's most respected philosopher of biological science, Elliott Sober, and probably the world's top expert in cladistics, Joe Felsenstein, both agree Norell's conclusions are unjustified. They would not agree that cladistics is "an empirical method", and they would appreciate that just being used throughout systematic biology doesn't mean it is always used properly. They understand the role of cladistic analysis in palaeontology better than Norell, and they believe his use of simplistic cladistics is wrong because dino-bird evolution was so complex. (For example, birds are closely related to dinosaurs, but in all likelihood were neither a descendant nor a sister group. And although Czerkas is almost certainly right to say early dromaeosaurs flew, and to dispute Norell's theory that dromaeosaurs were nonavian ancestors of birds, they probably were the ancestors of modern birds!) A sound and honest appraisal of the evidence supports few of Norell's claims, in particular that of having "an open mind". Original letters: 1: For the record, the claim that dromaeosaurs “could not fly” in June’s “The Dragons of Liaoning” is false. I was the first to publish on dromaeosaurs from Liaoning having asymmetrical flight feathers on their hands, which confirmed that these dromaeosaurs had actual wings and the ability to fly. The paper describing the fossils of these flying dromaeosaurs was one of several regarding fossil birds and pterosaurs included in The Dinosaur Museum Journal, Volume 1, August 1, 2002. For the past two decades, scientists using cladistics have claimed that dromaeosaurs were nonavian ancestors of birds, representing the best examples of how ground-dwelling dinosaurs supposedly evolved into birds. This has been one of the biggest mistakes ever made in paleontology. Perpetuating this mistake does a disservice to your readership. Stephen Czerkas Director, the Dinosaur Museum Blanding, Utah 2: It is not so easy to make a simple correlation between asymmetrical feathers and flight. Many flightless living birds display these feathers, but they are only one small part of a multipart flight apparatus. What does Czerkas mean by flight? Is it powered flight as in birds, gliding, or even parachuting? Asymmetrical feathers may confer an aerodynamic advantage in any of these, but whether the second two are necessarily homologous to bird flight is a complex question. Where are the data (like wind-tunnel or biomechanical studies) that support his claim that these animals were winged? Czerkas’s assertion that the use of cladistics is “one of the biggest mistakes ever made in paleontology” is laughable. Cladistics is an empirical method that estimates genealogy and is used throughout systematic biology. If Czerkas understood cladistic analyses, he would realize that none of us ever said that dromaeosaurs were the ancestors of birds. Rather, the current hypothesis places dromaeosaurs and troödontids together in a group that shares a common ancestor with birds. Could some basal dromaeosaurs fly? I have an open mind, but I await data and evidence rather than simplistic wing-waving. Mark Norell, curator of paleontology, American Museum of Natural History Finally (me again) I forgot to say that Norell et al wouldn't know evidence if they fell in a tub of it. John V. Jackson ____________________________________________________ Start your day with Yahoo! - make it your home page http://www.yahoo.com/r/hs
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