caravelair

sorry all, but i have one more problem i don't know enough about to argue efficiently. specifically, i mean the issues addressed on these websites:

http://www.godandscience.org/evolution/dinobird.html http://www.reasons.org/resources/con...hered_dinosaur

i'm hoping someone will know more about this than me. thanks for the help!

these claims seem to have been made rather recently, so i'm having trouble finding online resources.

Monkey

Try the JOURNAL OF DINOSAUR PALEONTOLOGY (which is not a professional peer review journal but could help you do more research). I didn't have a good read of the websites your provided but I believe there are several counter arguments to what I skimmed over, such as the birb metacarpal homology.

Worldtraveller

First off, let me say, I'm not an expert in biology or evolution, and I have learned more about both in the few months that I have been reading here than I ever thought I might.

A few points from the article...while seeming to be rigorous and scientific, it makes some rather bold judjements.

Huh? How does a question about a specific part of a theory completely falsify a theory? There aren't any real 'evolutionary scientists' that say the theory of evolution is 100% complete!
That's the beauty of the scientific process. It allows for rigorous review of data by other scientists!

Unfortunately, the creationists get a hold of a conflicting scientific paper, trot out a few out of context quotes, and say "see, this is wrong, therefore goddidit!" They are shamelessly taking this material out of context, using the hard, diligent work of scientists to further thier own ends.

So what if it turns out that the therapods weren't the true ancestors of modern birds, it just means that we need to keep digging. I think this is the concept that most eludes the creationist/IDiots.....the continuing quest to improve our understanding, and not write it off to a mythical being and leave it at that.

Cheers,
Lane

ps418

I can help you with this, but you'll have to wait at least a few days before I can get to it. A couple of quick points though.

The claim that Cuadipteryx is a secondarily flightless bird is unconvincing, but even if it were true, Caudipteryx would be fantastic evidence for the theropod ancestry of birds.

The claim that the similarities between Caudipteryx and theropods are simply the result of convergence is ridiculous.

The supposed non-homology of theropod and avian digits is indeed something of a puzzle. I'll have to look into that. Same with the lung function.

The claim that "the pelvic bones of the theropod dinosaurs look nothing like that of either modern birds or Archaeopteryx, but look very similar to that of modern reptiles, such as the crocodile," is so obviously contrary to fact that I look forward to posting the pictures to disprove it.

The claim, originally from Feduccia, that the fuzz associated with Sinosauropteryx is "frayed collagenous fibers beneath the skin," was not plausible when it was proposed and subsequently was decisively refuted. The simple feather-like structures on Sinosauropteryx and many other theropods from Liaoning, China have been proven to be external, integumentary structures. And in fact, there are now unquestionable dromaeosaurs with unquestionable avian feathers, with calumnus, rachis and barbs, so unless one if willing to call all dromaeosaurs birds, then theropod dinosaurs indeed had feathers.

Patrick

caravelair

thank you!

ps418

I'll discuss the so-called temporal discordance first. Both pages state that the bird-like theropod taxa are actually 20 million years younger than Archaeopteryx. Before commenting on that statement, it will be interesting to see how this time-discordance argument has evolved over the past decade. As recently as the mid 90's, opponents of the theropod-bird hypothesis were saying things like "most of the supposed similarities between urvogel [i.e., Archaeopteryx -ps418] and dinosaurs are seen in birdlike dinosaurs that lived 80 to 100 million years later" (Feduccia, 1994, p. 32). By 1996, they were musing that, to theropod-bird proponents "it is inconsequential that birdlike dinosaurs occur some 75 million or more years" after Archaeopteryx (Feduccia, 1996, vii). And by 1999, the gap closes even further, and Feduccia (1999, p.4740) wonders "why these superficially birdlike theropods only occur in the fossil record 30 to 80 million years after the appearance of the earliest known bird." Now, creationists and other opponents of the theropod-bird hypothesis are arguing for a discordance of 20 million years.

And wouldn't you know, more recent finds show that even this is a slight overestimate, since Sinovenator, a very bird-like theropod from from the lowest part of the Yixian Formation, dates to 128Ma, making it 17 million years younger than the Archaeopteryx specimens from the Jurassic of Germany (Xu et al, 2002). So, the time discordance has been dramatically reduced, from 80-100 million years, to 75 million years, to 30 million years, to 17 million years.

And despite the rarity of fossil lagerstatten, and of well-preserved fossil birds in general (note that both Archaeopteryx and the Liaoning theropods are from rare lagerstatten), there is now suggestive but incomplete fossil evidence that bird-like theropod groups, such as Dromaeosaurs (the same family of theropods as many of the Liaoning 'dino-birds'), did in fact exist prior to Archaeopteryx. Witmer (2002, p. 19) notes:

Also, there are some rather obvious inconsistencies with the critics' position that should be pointed out. For instance, from a YEC perspective, none of these specimens are 'too young' -- they are all far, far too old, some 70-145 million years too old. They lived ~70-145 million years before the creation, and occur in deposits that were formed over tens of millions of years. Indeed, a YEC cannot use any of this as an argument at all unless they accept the validity radiometric dating and stratigraphic correlation, which by definition no YEC can accept. From an OEC perspective which accepts the validity of radiometric dating and stratigraphic correlation, there is an entirely different potential inconsistency -- ghost lineages and lazarus taxa. These are taxa that are known from time A and time C, but are not known from intervening time B. Naish (1998) gives the example of Champosaurs, for which there are ghost lineages of at least 45 million years long, from the late Triassic to the middle Jurassic. And then of course there is the infamous coelacanth, for which there is a ghost lineage of about 65 million years. So unless Ross and other OEC's hold that these taxa were created, then went extinct, and then were created again tens of millions of years later -- unless they want to take that position, which I find highly unlikely- then they would have to acknowledge that whatever time discordance does exist for the theropod-bird hypothesis is not strong evidence against that hypothesis.

Finally, for Feduccia to complain of a temporal discordance is somewhat hypocritical. As Brochu and Norell (2000) point out, when you consider all of the proposed models for the ancestry of birds, including those of Feduccia, and consider the consistency of all of the nodes in the cladogram with the stratigraphic record, then the theropod hypothesis actually compares favorably to all the alternatives. So, each of these categories of critics are presenting somewhat inconsistent arguments.

I've got plenty to say on the other arguments. Give me some more time to get to them (I'm trying to reduce the number of hours I spend online).

Refs

Brochu, C.A. and Norell, M.A. 2000. Temporal congruence and the origin of birds. Journal of Vertebrate Paleontology 20(1): 197-200.

Evans, S.E. and Milner, A.R. 1994. Middle Jurassic microvertebrate assemblages from the British Isles. In: N.C. Fraser and H.-D. Sues (eds.), In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods, Cambridge University Press, Cambridge, 303-321.

Feduccia, A., 1994. The great dinosaur debate. Living Bird 13, 29-33.

Feduccia, A. 1996. The Origin and Evolution of Birds. Yale Univ. Press, New Haven, CT.

Feduccia, A., 1999. 1,2,3,=2,3,4: accomodating the cladogram. Proceedings of the National Academy of Sciences 96, 4740-4742.

Jensen, J.A., and Padian, K., 1989. Small pterosaurs and dinosaurs from the Uncompahgre fauna (Brushy Basin Member, Jurassic Formation:? Tithonian), Late Jurassic, Western Colorado. Journal of Paleontology 63, 364-373.

Metcalf, S.J., and Walker, R.J., 1994. A new Bathonian microverterate locality in the English Midlands. In: In: N.C. Fraser and H.-D. Sues (eds.), In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods, Cambridge University Press, Cambridge, 322-331.

Naish, D., 1998. Ghost lineage. Accessed online 6/25/03 at: http://www.dinosauria.com/jdp/evol/ghost.html

Witmer, L. M., 2002. The debate on avian ancestry: phylogeny, function, and fossils. In: Mesozoic Birds: Above the Heads of Dinosaurs, L. M. Chiappe and L. M. Witmer (eds.), University of California Press, Berkeley, 3-30.

Xu et al, 2002. A basal troodontid from the Early Cretaceous of China. Nature 415, 780-784.

Zinke, J., 1998. Small theropod teeth from the Upper Jurassic coal mine of Guimarota (Portugal). Palaontologische Zeitschrift, 72, 1/2, 179-189.

Patrick

Oolon Colluphid

:notworthy :notworthy :notworthy :notworthy :notworthy :notworthy

Is there some way to set up the system so it does that automatically every time Patrick posts?

If there were a god, we'd all have to thank him for Patrick. As it is, we can thank evolution

Oolon

MrDarwin

Not that I would ever dare to contradict Patrick, but I think this criticism is somewhat unfair because what YEC's are doing with this kind of argument is no different from what we sometimes do: granting some or all of an opponent's premise for the sake of argument, especially to point out contradictions and inconsistencies in their premises. What they are saying is that by paleontologists' own estimates the theropod "ancestors" of birds occur long after their "descendants" appear in the fossil record--although in making this argument YEC's commonly confuse ancestral species with ancestral groups (i.e., a group can continue to exist long after it has given rise to another group, speaking more colloquially than cladistically of course), and as Patrick points out, this is pretty much a non-issue given recent fossil discoveries.

ps418

Yes, I understand your point and agree with it completely. My point was simply that they -- YECs-- can not grant the premises of the argument. And as for those who do accept radiometric dating, there is no real inconsistency, since ghost lineages are a reality.

Patrick

MrDarwin

BTW I found a nice series of illustrated lectures on the evolutionary relationships of birds and other dinosaurs (keep clicking on "next lecture" to get to the really good stuff).