Uncommon Descent Serving The Intelligent Design Community

The claim that Sinosauropteryx had proto-feathers


It is fundamental to the methodology of science that hypotheses are proposed and tested. The human face of science surfaces when researchers enthusiastically endorse false positives, when hypothesis testing is less than rigorous, and when false dichotomies are proposed (i.e. if hypothesis B is falsified, hypothesis A is declared to be verified). The science of origins is well-supplied with examples of hypotheses that were once widely accepted as valid, but which are now discredited. A significant example has recently become apparent and is the theme of this blog. In 2009, Zhang et al. considered integumentary filaments of the theropod dinosaur Sinosauropteryx, knowing that Lingham-Soliar and colleagues had proposed that dino-fuzz filaments are structural collagen fibres released by processes of decay. The work reported that “melanosomes (colour-bearing organelles) are not only preserved in the pennaceous feathers of early birds, but also in an identical manner in integumentary filaments of non-avian dinosaurs”. This led Zhang et al. to conclude that the collagen fibre interpretation has been falsified and that the integumentary filaments were proto-feathers. In the summary provided by the editors of Nature:

“But it has been suggested that some of the structures that are not obviously feathers might actually be strands of collagen from under the skin. Zhang et al. refute this notion by demonstrating the presence in these structures of melanosomes – the characteristic bodies that give feathers their colours. Not only do they show that the feather-like structures of dinosaurs such as Sinosauropteryx really are akin to feathers, but also they can speculate in an informed way about their colour – which it seems was reddish brown or ginger.”

For more, go here.

Strawman kairosfocus
Maus, if ID proponents could predict the different stages of feathers, then why didn't they-- before they were discovered? Diogenes
Diogenes: "Why would bacteria on a decomposing collagen fiber make stripes?" Danke, that clears that up quite a lot. I wouldn't claim that archaic bacteria had melanosomes. But neither would I claim that bacterial growth cannot order itself in patterns. If you have ever seen salt-water fish tanks that rely on biofilters you will understand why. As a matter of taste and simplicity I would not prefer the bacterial hypothesis. "So he predicted four stages of feather evolution: I. single hollow shaft from one base. II Tuft of thin downy fibers growing from one base. III. Tree like structure with barbs. IV. Closed feather vane: tree “branches” grow hooks that link up." I have predicted that the evolution of automobile cooling systems: I. The liquid cooling. II. Passive liquid jackets. III. Active pumping of liquid. Respectively the have the examples T1, T-09, and CDO-R1 that exhibit these patterns. None can be said to be lineal descendants of one another from their notation, of course. But it still proves the progress of automobile evolution from the less efficient to the more efficient. And we can state that they were ordered, in time, by their simplicity on some metric of homology and create a nice phylogenic tree. Of course the T1 is the Volkswagen Type 1 (Beetle) which started production in 1945. The T-09 is the Ford Model T which began with the 1909 model. And the CDO-R1 is the Oldsmobile Curved Dash 1901 model. Maus
Diogenes @ 2 writes: "However, ARN does a good job of psychoanalzying the “metaphysics” — i.e. smearing – of those who know a feather when they see one. And isn’t that what ID is really about– psychoanalysis?" No. My interest here is in the science and what can reasonably be claimed from the evidences available. I fear your arguments draw heavily on the false dichotomy of thinking that "if I can only disprove the degraded collagen hypothesis, I can carry on defending proto-feathers". It appears to me that you have not digested Lingham-Soliar's critique. Much of it arises because he cannot verify the claims made for Sinosauropteryx. When he has data that allows quantification of the size of the alleged melanosomes, they turn out to be smaller and more variable than was claimed. It is a basic principle of science, is it not, that research findings should be repeatable and verifiable by others - so why does it not apply in this case? Some of the other points you make are addressed in Lingham-Soliar's most recent paper. I'm planning to post something on this paper - so these issues can be revisited then. David Tyler
Diogenes 'IV. Closed feather vane: tree “branches” grow hooks that link up.' Wow! who wudda believed it ;) PeterJ
I was accused of having out of date sources. Here's a more recent one: James Downard vs. that dim bulb Ann Coulter, on feathered dinosaurs and Archaeopteryx, quite entertaining. Diogenes
Or are you stating that variations in skin pigmentation based on location requires that we admit that the human dermis is proof that we’re feathered vertebrates?
You do not understand. Lingham-Soliar is theorizing that what look like melanosomes are bacteria that formed on what he calls decomposing collagen fibers. This theory is bad. Different types of melanosomes are arranged in stripes, which, if they're real, would make feathers with banded colors. Why would bacteria on a decomposing collagen fiber make stripes? Diogenes
When “protofeathers” are invoked, it usually has to do with “flight feathers”.
Actually they're opposites, explained below.
if a feather is captured in amber, how would you know that it is a “dino” feather?
That is a very good question. Richard Prum in 2003 proposed a detailed model of feather evolution based on developmental theories, that is, how do you grow a feather. He rejected the scale-to-feather theory, instead starting with a dermal placode. So he predicted four stages of feather evolution: I. single hollow shaft from one base. II Tuft of thin downy fibers growing from one base. III. Tree like structure with barbs. IV. Closed feather vane: tree "branches" grow hooks that link up. Birds living and extinct only have stages II and IV. Flight feathers are an ASYMMETRIC version of type IV. SFAIK, only found on birds. Dinosaurs with type IV only have SYMMETRIC versions of IV, and are presumably flightless. Prum predicted I and III before they were discovered. Feathered dinosaurs at first were found with either symmetric versions of IV, II, which looks like down and is called dino-fuzz, or III. In 2009 Beipiaosaurus was shown to have stage I feathers. So that's all four stages as predicted by Prum's model. So if the feathers in amber are Stage I or III, scientists think they are from dinosaurs, because these have never been seen on birds, living or extinct, but have been seen on dinosaurs. In the amber, you can definitely see I and a coiled-up II, exactly as predicted by Prum's model. The coiled-up II is probably dinosaur. You can see stage IV, but that could be bird or dinosaur. In fact, in the amber you can see what looks like a transitional form between II and III. Here is a semi-technical description of Prum's model, with many illustrations. Diogenes
I haven't the time, nor desire, to get into particulars of bird evolution: it is a very difficult area to navigate--even the experts have trouble. But I would just say that the basic argument comes down to what is meant by a "protofeather." IIRC, "dino-fuzz" is very much like down feathers; i.e., covering used for temperature stability. When "protofeathers" are invoked, it usually has to do with "flight feathers". The amber-captured dino "feathers" all look like some kind of "fuzz" except for the last; but it sure doesn't look like it's capable of flight. Be that as it may, I have a fundamental question: if a feather is captured in amber, how would you know that it is a "dino" feather? How do we know that it's not just a "bird" feather? Archeopteryx dates to 150 mya. And it has a modern flight feather. It would have been contemperaneous to dinosaurs. Again, how do we know that what is in the amber comes from a dinosaur and not some contemporary of Archeopteryx? PaV
Diogenes: "He cannot refute the striping in the tail of Sinosauropteryx, shown by the variations in melanosomes. What is his explanation for the striping?" Why should anyone need to? Or are you stating that variations in skin pigmentation based on location requires that we admit that the human dermis is proof that we're feathered vertebrates? I have no problem with the idea, or without, of proto-feathers. But your statements here seem rather incoherent. Maus
A fair enough criticism, but over at ENV I posted a list of feathered dinosaurs including many recently published ones. Lingham-Soliar's arguments are still just as bad. He cannot refute the striping in the tail of Sinosauropteryx, shown by the variations in melanosomes. What is his explanation for the striping? Bacterial decay makes stripes now? On what planet? How, how, does bacterial decay in alleged "collagen fibers" makes stripes? Since UD, ARN and Casey Luskin at ENV are now promoting the "collagen fiber" hypothesis for proto-feathers, I'll copy in here what I posted at ENV. The collagenists argue by analogy to Varanus [monitor lizard] which has collagen fibers in its skin, asserting that the fibers become spread out during decomposition. The problems with this are many: 1. In Sinosauropteryx, there are approximately 10 filaments preserved per millimeter, a very dense pelage. Alan Feduccia 1999 was wrong about fiber density. There are beautiful photos of Sinosauropteryx proto-feathers at Troy Britain's blog, alas not reproduced here [See: http://pigeonchess.com/2012/07/16/fuzzy-thinking-about-fuzzy-dinosaurs/]! No decomposing Varanus has collagen fibers like that! Compare Plate 1A and 1C in Kevin Padian et al (in Tanke & Carpenter 2001) to the figure of dermal collagenous fibers in Varanus (Feduccia 1999, 378). This goes for both Sinosauropteryx and NGMC 2123. 2. The alvarezsaur Shuvuuia deserti has identical integumentary structures (proto-feathers), which have been shown by chemical tests performed by Schweitzer et al (1999) to have been composed of beta-keratins, and could therefore not be dermal in origin. 3. None of the dromaeosaurs with proto-feathers under consideration here are known to live in a semi-aquatic environment, so the analogy to Varanus is invalid. 4. Lingham-Soliar (2003a, 2003b) argued by analogy to an ichthyosaur fossil that had alleged collagen fibers in its skin. Lingham-Soliar hypothesizes: "two possible scenarios are envisaged in Sinosauropteryx: either the bundles of tightly strung ligaments broke contact with the vertebrae during post-mortem decay and came to lie alongside the caudal vertebrae, or the skin possessed masses of strengthening fibers or rays vertically orientated to the long axis of the body" (2003a, pg. 6). No. If this hypothesis were true, the collagen fibers would lie along the midline. In fact, Sinosauropteryx has tufts of integument in many places, not just along the midline. To quote EvoWiki: "As Prum (2002) and Prum & Brush (2002) rightly ask, are we to believe that Beipiaosaurus had a 50-70 mm long ligament on its ulna? That NGMC 91 had a 35 mm ligament on its snout?" 5. Furthermore: in feathered dromaeosaurids, the integument is clearly external to, and reaches far beyond, the skin and bone (e.g. Sinornithosaurus cp.) In Lingham-Soliar's decayed ichthyosaur, the collagen fibers overlap bone or lie medial to the skin surface. RETURN TO CAUDIPTERYX. JUST A BIRD? And now I will return to the alleged "flightless bird". The Ruben & Jones 2000 paper asserting that Caudipteryx was just a [flightless] bird was out of date quite soon after publication, as new Caudipteryx material became available (Zhou & Wang 2000, Zhou et al 2000). Caudipteryx looks just like an oviraptor. To get technical, it has multiple characters synapomorphic of Oviraptorosauria, to name one, the presence of a mandibular fenestra. References: Feduccia, A. 1999. The Origin and Evolution of Birds, Second Edition. Yale University Press, New Haven. Lingham-Soliar, T. 2003a. Evolution of birds: ichthyosaur integumental fibers conform to dromaeosaur protofeathers. Naturwissenschaften 90: 428-432. Lingham-Soliar, T. 2003b. The dinosaurian origin of feathers: perspectives from dolphin (Cetacea) collagen fibers. Naturwissenschaften 90: 563-567. Padian et al. 2001. Feathered dinosaurs and the origin of flight. In: Tanke, D. H. & K. C. Carpenter (eds.), Mesozoic Vertebrate Life: 117-133. Prum, R. 2000. Longisquama fossil and feather morphology. Science 291 (5510): 1899c. Prum, R. 2002. The evolutionary origin of feathers and diversification of feathers. The Quaterly Review of Biology 77(3): 261-295. Ruben, J. & Jones, T. D. 2000. Selective factors associated with the origin of fur and feathers. American Zoologist 40(4): 585-596. Schweitzer et al. 1999. Beta-keratin specific immunological reactivity in feather-like structures of the Cretaceous alvarezsaurid, Shuvuuia deserti. Journal of Experimental Zoology 285: 146-157. Zhou, Z. & Wang, X. 2000. A new species of Caudipteryx from the Yixian Formation of Liaoning, northwest China. Vertebrata PalAsiatica 38: 111-127. Zhou et al. 2000. Important features of Caudipteryx—Evidence from two nearly complete new specimens. Vertebrata PalAsiatica 38: 241-254. Diogenes
Diogenes: Here's a quote from your link: In two recent papers, Theagarajen Lingham-Soliar (2003a, 2003b) has argued that detailed similarities between fossilized ichthyosaur and recently buried bottlenose dolphin (Tursiops truncatus) collagen fibers strongly suggests homology between the two. Lingham-Soliar hones his sights on two studies in particular: Currie & Chen (2001) and Xu et al (2001), and it is so littered with errors that its well worth quoting at some length. The most recent papers considered in this link come from 2003!! The link says that the time the page was updated was in 2008. But there are no papers listed later than 2003. Who's being "desperate" here? And we here at ID are prepared to psychoanalyze you: and it doesn't look pretty. PaV
Ah, when I read the whole post at ARN I see I am mistaken: the creationists are in agreement about "collagen fibers." Now if you look at a close up photo of sinosauropteryx's integumentary structures, they look nothing, nothing, like the collagen fibers on the monitor lizard. They are far too dense. Moreover, these collagen fibers are only found on semi-aquatic reptiles. There is no evidence that any of the 34, that's 34, species of feathered dinosaurs were semi-aquatic. This "collagen fiber" hypothesis is considered in detail here. It's desperation. The "collagen fiber"/ aquatic lizard hypothesis is dead in the water (pun intended). However, ARN does a good job of psychoanalzying the "metaphysics" -- i.e. smearing-- of those who know a feather when they see one. And isn't that what ID is really about-- psychoanalysis? Diogenes
Um, over at Evolution News & Views, Casey Luskin, in his post on "Dino-Fuzz" has been promoting the theory that dino proto-feathers are still just collagenous fibers. Read Luskin's comments there-- it's not in the post. Perhaps Casey didn't get the memo? So am I to understand that ENV defends the "collagen fiber" theory, while UD considers it disproven? Diogenes

Leave a Reply