You have begun with a quotation from a
press release by Alan Feduccia from 1996, that I have not seen cited previously in the thread. Can you keep track of your references, please?
ex libres writes:
It is a short article you know. However, here are some points you can address.
"A report on the discovery appears in the Nov. 15 issue of the journal Science. Besides Feduccia, [Biologist and ORNITHOLOGIST] authors are Dr. Lianhai Hou of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing and Dr. Larry D. Martin and graduate student Zonghe Zhou of the University of Kansas' Natural History Museum."
... Feduccia said, they have found fossils of a modern-type, probably warm-blooded bird they call Liaoningornis together with Confuciusornis. Unlike the latter, the former had a keeled sternum, which is the earliest evidence of that distinctly bird-like structure, one that acted as a pump for air sacs in the lungs and facilitated longer flights. All modern flying birds show that keeled breastbone. "We would expect that the common ancestor of the two groups -- which we call `Sauriurine' for reptile-like and `Ornithurine' for bird-like -- predates Archaeopteryx and that we may reasonably search for birds in Middle Jurassic and older beds," Feduccia said.
"This exacerbates one of the most obvious conundrums facing the theory that birds descended from dinosaurs. The dinosaurs thought to be most like birds are primarily Late Cretaceous in age and are younger than Archaeopteryx by more than 76 million years."
Feduccia will be immediately familiar to people interested in this subject. He is, like every other scientist working on these fossils, an evolutionist, who recognizes that
all the fossils we are discussing are transitional. The press release omits aspects of Liaoningornis which distinguish it from birds in the present; such as teeth. The questions at issue are some of the details of phylogentic relationships.
Basically, this release focuses on the question of how far back we go for the last common ancestor of birds and dinosaurs. It does not call into to question the status of Archaeopteryx, or Lioningornis, or Confuciusornis, as transitional forms that show aspects of the lineage of birds and their relationship to reptilian ancestors.
Most scientists consider that birds are descended from theropod dinosaurs. Feduccia and a handful of others consider the common ancestor to be further back -- though technically still an early dinosaur.
One contentious problem with Liaoningornis is dating of the strata in which this fossil was found. One view dates it from 137 to 141 million years bp; and others date it as recently as 121 million years bp. Although these ages are similar to within 20%, we now have so many transitional forms that accurate ages are needed to to help place them in relation to each other.
Feduccia puts his finger right on the button in
Ornithologist and Evolutionary Biologist Alan Feduccia Plucking Apart the Dino-Birds (Discover Vol 24, No 2, Feb 2003):
Creationists have used the bird-dinosaur dispute to cast doubt on evolution entirely. How do you feel about that?
Creationists are going to distort whatever arguments come up, and they've put me in company with luminaries like Stephen Jay Gould, so it doesn't bother me a bit. Archaeopteryx is half reptile and half bird any way you cut the deck, and so it is a Rosetta stone for evolution, whether it is related to dinosaurs or not. These creationists are confusing an argument about minor details of evolution with the indisputable fact of evolution: Animals and plants have been changing.
Writing in volume two of their Modern Creation Trilogy on this matter in regard to Archaeopteryx, Henry Morris and John Morris stated:
"Archaeopteryx is a mosaic of useful and functioning structures found also in other creatures, not a transition between them. A true transitional structure would be, say, a sceatherthat is, a half-scale, half-featheror a linghalf-leg, half-wingor, perhaps a half-evolved heart or liver or eye. Such transitional structures, however, would not survive in any struggle for existence (1996, 2:70)."
Can't mince words on that one... that is ignorant nonsense. What Morris calls a true transitional structure is a strawman and has nothing to do with evolutionary biology. What evolution requires, and finds, are well adapted transitional forms made up of a mosaic of useful and functioning structures showing relationships to two different known distinct forms.
Of your other points, which I have not quoted, (1) and (2) are as expected for transitionals. (3) is an assertion without argument or evidence. (4)..(7) are from Feduccia's side of the argument for theropods being a distinct side branch to birds; which is a distinct matter entirely, of no relevance whatsoever to the obvious transitional status of the fossils in question.
Cheers -- Sylas
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