CharlieM wrote:Theropod:
CharlieM wrote:
theropod:
There's one small problem with your example. All birds are the descendants of theropod dinosaurs. .
Don't you mean, "In my view, all birds are the descendants of theropod dinosaurs".
No. I meant what I wrote. There is a mass of supporting evidence that I accept because no other evidence exists to overturn this. I don't think I will supply even a tiny portion of that evidence here as "in my view" it would be wasted on you. Should you question this you are welcome to offer any empirical evidence that, "in your view", would counter my assertion. I'm betting you can't and won't.
That is the problem with people who believe the current paradigm. No matter if 99.99 percent of scientists believe that there is sufficient evidence to put a theory beyond doubt, if other scientists believe there is evidence that refutes or puts in doubt that theory, then you cannot just glibbly treat it as fact. In the past, how many views held by the vast majority of scientists turned out to be wrong? I thought that was what science was all about, always questioning current understanding.
Actually it means that .1 percent of scientists are trying to overcome a accepted theory. This does not make the accepted theory not fact, since there is evidence to support the assertion. It is the job of the .1 percent to show the 99.99 percent of scientists that they are wrong. For this case I suggest reading your own links.
As for empirical evidence to counter your assertion:
http://www.ucmp.berkeley.edu/diapsids/avians.htmlSome researchers today do not agree that dinosaurs gave rise to birds, and are working to falsify this theory, but so far the evidence for the theory has swamped their efforts. If they were to conclusively establish that birds are more likely descended from another group (Crocodylomorpha, the group containing crocodiles, has been suggested), that would be a major upheaval in our knowledge of phylogeny. One single well-preserved fossil bird unequivocably of Triassic age might shed some doubt on the theory of the maniraptoran affinities of birds. That would be a major find. Some bird-like fossils have been presented as Triassic birds, but so far have not held up under peer review. Such is the dynamic nature of science.
From this link:
Some researchcers have raised issues that may seem to make the theropod origin of birds difficult to support, but these difficulties are more illusory than substantial. One proposed difficulty is the gap in the fossil record between the first known bird (Late Jurassic) and the dromaeosaurs, probable sister group of birds (Early Cretaceous). This overlooks the blatant fact that other maniraptoran coelurosaurs, such as Ornitholestes, Coelurus, and Compsognathus, are known from strata of Late Jurassic age. If other maniraptorans were there, it logically follows that the ancestors of dromaeosaurs were there. Fragmentary remains of possible dromaeosaurs are also known from the Late Jurassic.
Other arguments, such as the putative differences between theropod and bird finger development, or lung morphology, or ankle bone morphology, all stumble on the lack of relevant data on extinct theropods, misinterpretations of anatomy, simplifying assumptions about developmental flexibility, and/or speculations about convergence, biomechanics, or selective pressures. The opponents of the theropod hypothesis refuse to propose an alternative hypothesis that is falsifiable. This is probably because there are no other suitable candidates for avian ancestors. "Thecodonts" are often promoted as such, but this is an obfuscatory, antiquated term for a hodgepodge of poorly understood and paraphyletic, undiagnosible reptiles. The problems cited by such opponents for theropods are often more serious for the "thecodont" pseudo-hypothesis. Finally, such opponents also refuse to use the methods and evidence normally accepted by comparative evolutionary biologists, such as phylogenetic systematics and parsimony. They rely more on an "intuitive approach," which is not a method at all but just an untestable gestalt impression laden with assumptions about how evolution must work.
The "controversy" remains an interest more of the press than the general scientific community. There are more interesting issues for scientists to explore, such as how flight performance changed in birds, what the earliest function(s) of feathers was(were), when endothermy arose in some archosaurs, which group of theropods was ancestral to birds, how theropod ecology changed with the acquisition of flight, why some bird groups survived the Cretaceous extinction of other dinosaurs, etc.
Without its feathers, Archaeopteryx looks much like a small coelurosaur such as a dromaeosaurid or troodontid.
The facts are resoundingly in support of a maniraptoran origin for birds; certainly a theropodan origin at the very least. So when you see a hawk diving to snatch a dove, or an egret darting for fish, or an ostrich dashing across the African savanna, know that you are gaining some insight into what the extinct dinosaurs were like. However, do note that extant (living) birds are quite different from extinct dinosaurs in many ways, so it's not safe to assume that all dinosaurs are the same. For that matter, extant birds are quite different from Jurassic and Cretaceous birds. Time passes, the environment changes... life evolves. Extant birds have been separated evolutionarily from the other coelurosaurian dinosaurs for some 150 million years, so they do look, act, and function quite differently, but science has shown us that they are closely linked by their common evolutionary history.
This link is saying that although there are some researchers that object to the theropod origins of modern birds, the evidence they provide is weak and insubstantial. Way to check your source. Next:
http://www.geotimes.org/june02/WebExtra0627.htmlThe ancestors of birds are widely believed to be dinosaurs, but the specifics of bird origin are still unclear. Now, geologists have found footprints in northwest Argentina that are evidence for the oldest bird-like creatures discovered.
"This finding poses many questions regarding the origin of birds and the relationships of this unknown group of theropod dinosaurs with other groups of dinosaurs," says Ricardo Melchor from the Universidad Nacional de La Pampa in Argentina, and lead author of the group that published its findings in this week's Nature. "It's significant because we find footprints with morphology identical to modern birds in rocks that predate, by 55 million years, the first record of true Aves."
If they have "morphology identical to modern birds" why is Ricardo Melchor calling them an "unknown group of theropod dinosaurs"? Surely he is making an assumption because of his prior belief.
Even Melchor has said though, IN THAT LINK, that this does not disprove the theropod bird hypothesis. So far no skeletal remains have been found of a creature who could produce such tracks and so far, there a wide array of explanations. Only the "Birds are not Dinosaurs" supporters are overly concerned about this. Most in the scientific community view it as interesting but not enough to topple a huge amount of evidence.
http://www.nature.com/nature/journal/v417/n6892/full/nature00818.htmlThe study of fossilized footprints and tracks of dinosaurs and other vertebrates has provided insight into the origin, evolution and extinction of several major groups and their behaviour; it has also been an important complement to their body fossil record
1, 2, 3, 4. The known history of birds starts in the Late Jurassic epoch (around 150 Myr ago) with the record of Archaeopteryx
5, whereas the coelurosaurian ancestors of the birds date back to the Early Jurassic6. The hind limbs of Late Triassic epoch theropods lack osteological evidence for an avian reversed hallux and also display other functional differences from birds
7. Previous references to suggested Late Triassic to Early Jurassic bird-like footprints have been reinterpreted as produced by non-avian dinosaurs having a high angle between digits II and IV
8, 9 and in all cases their avian affinities have been challenged
10. Here we describe well-preserved and abundant footprints with clearly avian characters from a Late Triassic redbed sequence of Argentina
11, 12, at least 55 Myr before the first known skeletal record of birds. These footprints document the activities, in an environment interpreted as small ponds associated with ephemeral rivers, of an unknown group of Late Triassic theropods having some avian characters.
Yet again they assume an unknown group of theropods.
And what do you suppose? That modern birds actually lived in that era? Yeah because that makes more sense than assuming a group of unknown theropods.
To bad, Feduccia left out cladistics in his research. That right there makes it weaker. As for Martin, he is a researcher on Caudipteryx, and disagrees with the general consensus, why does his opinion matter more than others?
They are a few mavericks who wish to attempt to disprove a well accepted theory with a huge amount of evidence in support of it. They have their work cut out for them. As your first link states, most evidence against the birds are dinosaurs theory is weak and not enough to discredit the theory. I think I am going to trust the consensus on this one, unless of course Charlie you want to provide compelling evidence on contrary. The evidence these scientists give are easily shrugged off by the scientific community. Do you have something better?
by 
