ps418

I'm placing this discussion in a new thread rather than the bird thread because the bird thread is already burdened with too many illustrations.

According to the God and Science article Demise of the 'Birds are Dinoaurs' Theory:

Let's start with the reference, which is wrong. Reference 6 is to a commentary in Science by Gibbons, and does not include the quoted text. However, it does make a reference to the now-refuted hypothesis (Geist 1997; Feduccia, 1999), that the integumentary structures of Sinosauopteryx were "frayed collagenous fibers from beneath the skin" that were originally part of a dermal frill running along the dorsal midline of the body. This was proposed following the discovery of the first specimen of Sinosauropteryx prima, a dromaeosaurid theropod with filamentous structures evident around the body. The author of the God and Science article, and numerous other creationist articles which proclaim this hypothesis as fact, seem unaware that this claim was highly questionable even when it was proposed, and subsequently has been proven false. As reported by Chen et al (1998), new specimens of Sinosauropteryx prima showed the filamentous structures not only along the dorsal surface of the neck and back, as might be expected for a dermal frill, but also along the margins of the tail, with patches on the side of the skull, humerous and ulna.

Other nonavian theropods from the same deposits, for instance the therizinosaur Beipiaosarus inexpectus have the same type of simple filamentous structures as Sinosauroptryx prima present on both fore- and hindlimbs, a distribution which again clearly inconsistent with their being part of a sagitally-placed dermal frill. While these structures are not identical to feathers of modern birds, they may well be feather homologues and/or represent a primitve stage of feather evolution. These structures are in fact integumentary structures, they were on the outside of the skin, they clearly did not run down only the dorsal midline of the body like a dermal frill, and both macroscopically and under magnification they look nothing like collagen fibers. Also interesting in this context is the report by Schweitzer et al (1999) that the filamentous structures preserved around the head of Shuvuuia deserti were both hollow and composed of beta keratin. If both observations are correct, then these structures may well have been feather homologues, since feather rachi are the only type of integumental cover that is both hollow and composed of beta keratin. At present it is not possible to say how widely distributed such structures were amongst dinosaurs, but they may have been more widely distributed than previously assumed.

More importantly, recently discovered theropods show a more complex integumentary structure, with complex branching, in some cases covering nearly the entire body (e.g. Ji et al, 2001; Xu et al, 2001). Examples include Sinornithosaurus millenii, Microraptor zhaoianus, and M. gui (Norell, 2002; Xu et al, 1999; Xu et al, 2000; Xu et al, 2003). Regarding the integumentary structures present on the dromaeosaurid theropod Sinornithosaurus milenni, Xu et al (2001, p. 200) noted the presence of "two types of branching structure that are unique to avian feathers: filaments joined in a basal tuft, and filaments joined at their bases in series along a central filament." Feathers are the only known branching integumental structures in vertebrates, and the structure of the 'feathers' of Sinornithosaurus millenii match extremely well stages II and IIIA predicted by Prum's (1999) developmental model of feather evolution. Also, though barbules are not evident in these specimens, they may well have been present, given how well-ordered the barbs are (without barbules, the barbs would be much more clumped together). The specimen pictured in Nik's post above, NGMC 91-A, is definitely a dromaeosaurid and is definitely very similar to previously described specimens referred to Sinornithosaurus.

The newly described specimens of the newly described species Microraptor gui, specimens IVPP V13352 and TNP00996, not to be confused with Microraptor zhaoianus, are even more compelling (Xu et al, 2003; Prum, 2003). Here we have a theropod which can be "unequivocally referred to Dromaeosauridae" (Xu et al, 2003, p. 336) possessing unequivocal 'avian' feathers (see for instance, figure 2e in Xu et al, 2003).



So, while it may take creationists a few decades to realize it, this chapter of the debate is now over: dromaeosaurid theropods, long thought to be avian ancestors based on skeletal morphology, did indeed possess feathers, complex, uniquely(?) avian structures. The challenge now is for creationists to explain why this group --so far to the exclusion of all other tetrapod groups-- possessed these structures.

Refs

Chen et al, 1998. An exceptionally well-preserved theropod dinosaur from the Yixian Formation of China. Nature 391, 147 - 152.

Geist, N.R., Jones, T.D. and Ruben, J.A. (1997) Implications of soft tissue preservation in the composognathid dinosaur, Sinosauropteryx. Journal of Vertebrate Paleontology 7 (suppl. to no. 3): 48A.

Gibbons, 1997. Plucking the feathered dinosaur. Science 278, 1229-1230.

Norell et al, 2002. Palaeontology: 'Modern' feathers on a non-avian dinosaur. Nature 416, 36 - 37.

Ji et al, 1998. Two feathered dinosaurs from northeastern China. Nature 393, 753-761.

Ji et al, 2001. The distribution of integumentary structures in a feathered dinosaur. Nature 410: 1084-1088.

Prum, 1999. Development and evolutionary origin of feathers. Journal of Experimental Zoology 285, 291-306.

Prum, 2003. Dinosaurs take to the air. Nature 421, 323-324.

Schweitzer et al, 1999. Beta-keratin specific immunological reactivity in feather-like structures of the Cretaceous alvarezsaurid, Shuvuuia deserti. Journal of Experimental Zoology (Mol Dev Evol) 285, 146-157.

Xu et al, 1999. A therizinosauroid dinosaur with integumentary structures from China. Nature 399, 350-354.

Xu et al, 1999. A dromaeosaurid dinosaur with a filamentous integument from the Yixian Formation of China. Nature 401, 262-266.

Xu et al, 2000. The smallest known nonavian theropod dinosaur. Nature 408, 705 - 708.

Xu et al, 2001. Branched integumental structures in Sinornithosaurus and the origin of feathers. Nature 410, 200 - 204.

Xu et al, 2003. Four-winged dinosaurs from China. Nature 421, 335-340.

Zhang, F., and Zhou, Z., 2000. A primitive enantiornithine bird and the origin of feathers. Science 290, 1955-1959.

Patrick

MrDarwin

Because they're just birds.

Actually, I'm serious. That's exactly what the creationists are going to say, and they'll quote Feduccia or somebody else to say they're just secondarily flightless birds. It wouldn't surprise me one bit if they're saying it already. (But it does make me wonder if Feduccia et al. have had anything to say about these feather-like structures lately.)

ps418

Nope. Feduccia and friends are already on record as saying that Sinosauropteryx is just a dino with convergent bird-like features. To now place Sinosauropteryx in dromaeosauridae and Sinornithosaurus and Microraptor in aves would be ridiculous. And unlike Protarchaeopteryx and Caudipteryx, which Fedducia did suggest were a flightless bird, Sinornithosaurus and Microraptor retain the features that are diagnostic of dromaeosauridae. But even if you wanted to place all of these specimens in aves, that would not obscure one bit their relationship with the rest of the the theropoda. In fact, they would simply replace Archaopteryx as the most theropod-like basal birds. And, you'd have to place all the dromaeosaurs in aves, including those like deinonychus, which these critics have beeen saying for years are just dinosaurs, and dromaeosaurus, which is a pretty typical theropod. I dont see any easy, taxonomic gerrymandering way out for Fedducia or the creationists.

Patrick

Non-praying Mantis

Actually, those fossils are the separately created "feathered dinosaur kind" not "theropod dinosaur kind" or "bird kind"



NPM

Fedmahn Kassad

I recently had an e-mail correspondence with Storrs Olson from the Smithsonian. In his reply, he made it quite clear that he is not swayed in the least by these recent finds. I won't share specifics of the e-mail without his permission, but he made some interesting accusations against paleontologists over this issue.

Interestingly enough, he also copied Feduccia in his response to me.

FK

MrDarwin

Yes, I think you've nailed it. They'll call them "mosaics" along the lines of the duck-billed platypus.

Fedmahn Kassad

Here is what Jon Sarfati had to say on the matter:
http://www.answersingenesis.org/docs2002/0309bpm.asp

No, he doesn't rule it out, but he argues pretty strongly against it in his writings. It's like he's saying "You are WRONG, WRONG, WRONG, but so what if you are right?" Someone is just seeing the handwriting on the wall and hedging his bets.

FK

Nic Tamzek

Or you can take Jonathan Wells' line,

"It's just another feathered dinosaur"

...like it's no big deal.

ps418

I checked out Sarfati's comments on Microraptor, and he doesn't seem to commit one way or the other. But the fact that he is so skeptical of the authenticity of the feathers leads me to think he leans towards Microraptor being a dinosaur. He does correctly note that Xu himself, the lead author of the paper, was the one who exposed 'Archaeoraptor' as a chimeric fossil, and thus "it’s extremely unlikely that the lead researcher Dr Xu Xing himself would ever be part of any deliberate fraud."

Also, Sarfati cites as tenable the discredited hypothesis that the integumentary structures in Sinosauropteryx are collagen fibers. Also, oddly enough, he seems to accept without any question that Caudipteryx is a flightless bird with genuine feathers, though here he seems to just be following Feduccia's lead. I wonder why he doesn't question the authenticity of of the feathers of Caudipteryx?

Oh yeah, Sarfati also wonders why so many of these specimens come from Liaoning? "It certainly seems strange that all these ‘feathered dinosaurs’ come from a single province of China—the same place as the Archaeoraptor hoax came from." Of course, its not 'strange' at all, certainly not any stranger than any other laggerstatten that preserves soft parts that usually are not preserved (e.g. Burgess Shale, Solnhofen Limestone).

Patrick

ps418

A couple more points. Sarfati states that "there is nothing in the creationist model that states that dinosaurs could not have feathers." Well, duh! There's nothing in the creationist 'model' that explains why characters are distributed amongst taxa the way that they are. However, Sarfati is being a little disingenuous here. Its not like we're finding feathers in the dinosauria as a whole, or saurischians as a whole, or even theropods as a whole. As Feduccia has been kind enough to point out for several years now, there are several examples of dinosaurs, including theropods, with well-preserved skin impressions yet lacking feathers, arguing against too wide a distribution of feathers or feather-like integument with the dinosauria. Currently these structures are only known from the most bird-like theropods. Also, there are no known Triassic feathers, the earliest known being those of Archaeopteryx in the mid-late-Jurassic, while feathers are pretty widely known from the Cretaceous -- China, Mongolia, Spain, Lebanon, Russia, Australia, Brazil, United States, Kazahkstant, Japan, and Canada (Kellner, 2003).

Another point that I didn't mention is about the distribution of feathers on Microraptor's legs, making it the only known tetrapteryx. This provides evidence that Microraptor may well have been capable of gliding, consistent with an arboreal origin of bird flight, but not with a cursorial origin of bird flight.

I'm sure Feduccia must be conflicted about this, given that he has always supported an arboreal origin for flight, and Microraptor is the perfect example of an arboreal 'protavis,' much better than the crappy non-theropod Triassic candidates he's championed over the years, such as Longisquama. Also, I think that while the tetrapteryx condition is a perfect functional intermediate, it does not sit well with the hypothesis that Microraptor is a secondarily flightless animal. From the commentary on Xu et al (2003) by Prum:


Refs

Kellner, 2003. A Review of Avian Mesozoic Fossil Feathers. In: Mesozoic Birds: Above the Heads of Dinosaurs, L. M. Chiappe and L. M. Witmer (eds.), University of California Press, Berkeley, 389-420.

Prum, 2003. Dinosaurs take to the air. Nature 421, 323-324.

Patrick