Jul 05 2012

Feathers More Common Among Dinosaurs

The story of feathered dinosaurs is one of the strongest success stories for evolutionary theory, and continues to be a thorn in the side of evolution deniers. They cannot help but expose their ignorance and deception when they clumsily try to deny the implications of feathered dinosaurs. So I tend to revel, just a bit, in each new significant discovery of a feathered dinosaur. The latest discover, recently published in PNAS, provides evidence that feathers were even more common among dinosaurs than previous evidence demonstrated. There is some debate among experts about how prevalent protofeathers and feathers were, and so a new piece of solid fossil evidence helps clarify the debate further.

After Darwin published his theory of evolution one of the early challenges to the idea of evolution, which includes the claim that all life on earth is related through common ancestors, was that there were significant gaps between major groups of living creatures. Birds, for example, seem to be their own group without a close connection to any other group. They are, of course, related to vertebrates. But if evolution were true then there must be fossil evidence connecting birds to another group, such as reptiles.

Right around that time the first specimens of Archaeopteryx were discovered (the London specimen in 1861 and the Berlin specimen in 1874). These are beautiful transitional fossils showing features of both theropod dinosaurs and birds – exactly as Darwin predicted. For decades Archaeopteryx stood as the sole species bridging birds and dinosaurs, and creationists did everything they could to deny the implications of this fossil. They tried calling it a hoax, then just a regular dinosaur, then just a regular bird. They also argued that, whatever it is, there is no proof that it is actually transitional between dinosaurs and birds – a non sequitur that betrays their lack of understanding of evidence in science.

The fact remains that if evolution is true, and birds did evolve from dinosaurs, then we would expect there to be many fossil species occupying the morphological space between birds and dinosaurs (the vast majority of which will not be on the exact line from dinos to birds, but on another phylogenetic path within that evolutionary space). Incidentally, many paleontologists now include birds in the clade of dinosaurs and call what we traditionally think of as dinos “non-avian dinosaurs.” But I will just use the term “dinosaur” in this common sense.

Further, starting around the 1980s paleontologists started finding the motherload of feathered dinosaurs in China, with numerous species fleshing out the timeline between dinos and birds. There were specimens both closer to birds than Archaeopteryx and others closer to non-avian theropods. There are specimens with protofeathers not yet adapted to flight. In other words, there is a branching bush of feathered dinosaurs in the right time to represent a group of animals from which birds evolved. That particular gap in the evolutionary tree of life was nicely filled in.

Further still, paleontologists started to discover specimens of known dinosaurs, like velociraptor and T-rex, that show signs of feathers. It now seems that this whole group of dinosaurs, known as the coelurosaurs (a subgroup within the theropod dinosaurs) has some kind of feather-like structures.

The new discovery is significant because it is a well-preserved specimen, showing clear protofeather filaments, in a theropod dinosaur that is closer to the trunk (base) of that group than any previous specimen. This means that feathers evolved earlier in the theropod clade than previous evidence demonstrated, and that, therefore, feathers were even more common within theropods. The new species is called Sciurumimus albersdoerferi and is a juvenile.  From the abstract:

Sciurumimus albersdoerferi represents the phylogenetically most basal theropod that preserves direct evidence for feathers and helps close the gap between feathers reported in coelurosaurian theropods and filaments in ornithischian dinosaurs, further supporting the homology of these structures.

The following cladogram demonstrates the relevant relationships:

Previous evidence showed feathers in theropods from Dilong to Confuciusornis. Sciurumimus takes feathers back four branching points on the above cladogram, meaning that it evolved earlier in the group and that many more dinosaurs likely had some kind of feathers. Of course, we may discover other specimens that bring it back further still. This is likely not the final word on the earliest origin of feathers within theropods.

I also notice that this specimen is a juvenile. Perhaps in some species feathers existed only in the young dinosaurs, as an adaptation for insulation, for example, and that adult specimens lost their downy feathers. Therefore we may need to find well-preserved juveniles (like this specimen) to really find out how prevalent protofeathers were.

Creationists are stuck arguing that it is nothing but a coincidence that the group hypothesized to the related to modern birds is turning out to have feathers and protofeathers as a common feature. Nothing changes the fact, however, that this is a verification of a prediction made by evolution. The ability to successfully make predictions about what will be discovered in the future is powerful vindication for any scientific theory.

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26 responses so far

26 Responses to “Feathers More Common Among Dinosaurs”

  1. ccbowerson 05 Jul 2012 at 10:31 am

    I’m sure this is a common thought, but as a kid I used to wish that I could go back in time for a few hours to see what these animals really look like. Admittedly, I occassionally have this thought today but then realize that this opportunity shouldn’t be wasted on a me, but should go to someone who has spent his or her whole like studying animals in this era.

    I also wonder how accurate we would be piecing together modern animals with the same amount of evidence/data that we have for dinosaurs. How would we illustrate elephants, giraffes, lions, whales, ostriches, etc. I imagine that we might piece together a trunkless elephant, a mean looking ostrich (instead of the goofy looking creature that it is), etc.

  2. nybgruson 05 Jul 2012 at 11:44 am

    I don’t like these findings at all. It means that all the books and magazines I read about dinosaurs as a kid most likely had the drawings all wrong… and that the images I have in my head are probably wrong too.

    I knew, of course, that this would likely be the case anyways (even as a kid my science teachers actually discussed this fact with us*) but now that I am old and set in my ways, this is an affront to my sensibilities.

    Lets pretend this “evidence” doesn’t exist so that my childhood imagery can still be considered equally valid in the “debate” about dinosaur morphology.

    *yes, I actually had real science teachers. All my life. Except for one. In the 6th grade she tried to convince us that B and T cells were called that because when you looked at them under the microscope they looked like little letter B’s and T’s. I called BS, she argued and said she was the teacher and knew better. I wouldn’t let it drop. I ended up getting sent to the principle’s office. The next day I brought in my biology text (I was concurrently taking a night class in introductory biology at the local community college) and showed her the relevant pages. At least she stopped arguing with me after that. But yes, the remainder of all my science teachers for my entire pre-college education were not just good, but actually quite amazing. It makes me sad to think about all these kids getting shortchanged in amazing education because of creationist BS and budget cuts.

  3. SARAon 05 Jul 2012 at 12:34 pm

    ccbowers

    I want a Jurassic Park. I want us to find a way to clone them and set up a preserve for them. I suppose there might be the odd accident (human meal), but in the name of science and entertainment, is that so much to ask? I’m sure the keepers wouldn’t mind.

    It seems more likely and practical to me than time travel. Although, we would still be dealing with the many of the same problems we have with various fossils. We would only be looking at the tiniest fraction of a huge swath of species over huge amounts of times.

    But how could you possibly cover all the geography and time span of Dinosaurs with time travel? It would take centuries of scientists.

    It seems more immediately practical to just clone what you find in the present…if one could actually get some DNA. The problem of viable DNA is a technicality that I will relegate to nil since this is a fantasy in any case. I use the creationist methods in that regard.

  4. Heptronon 05 Jul 2012 at 1:26 pm

    Dr. Novella.

    Based on what we have heard in the past, particularly SGU Podcast 97 (I think) with the interview about the Australian expat in China, can we trust any fossils coming out of China? When and how have they been verified?

  5. Steven Novellaon 05 Jul 2012 at 2:10 pm

    Heptron,

    That is a reasonable point. There was, in fact, one fraudulent fossil out of China (crafted by a non-scientist to sell to the scientists). Since then there has been much more scrutiny of new fossil finds – not accepting second hand fossils. There are also scientists from other countries involved. And in any case any new fossils are closely inspected and if they were a fraud it would quickly be spotted (as it was in the one known case).

  6. elmer mccurdyon 05 Jul 2012 at 6:12 pm

    So what’s the deal with beaks? How is that an advance over big sharp dinosaur teeth?

  7. Ori Vandewalleon 05 Jul 2012 at 7:45 pm

    Beaks aren’t an advance over big sharp dinosaur teeth; they’re an adaptation to a different situation. Darwin’s finches, for example, use beaks to crack open nuts. Sharp teeth are better for tearing things (meat) apart.

  8. Steven Novellaon 05 Jul 2012 at 7:57 pm

    What ori said. Evolution is adaptation to your immediate environment and lifestyle. It is not an inexorable “advance” or rise up the chain or anything like that. Birds are just different than non-avian dinosaurs, not necessarily “better” or more advanced.

  9. elmer mccurdyon 05 Jul 2012 at 8:59 pm

    But I’m wondering how come all birds have beaks, even carnivorous ones? Presumably they’re all just descended from an ancestor that happened to be adapted that way. Me, I would have given the meat eaters their teeth back though.

  10. ccbowerson 05 Jul 2012 at 9:29 pm

    “Presumably they’re all just descended from an ancestor that happened to be adapted that way.”

    There are birds with “toothed” beaks. Although they are not really teeth, they do serve some of the same functions as teeth.

  11. elmer mccurdyon 05 Jul 2012 at 10:11 pm

    Yeah, I’ve noticed that about the scary hissing geese in the park.

  12. daedalus2uon 05 Jul 2012 at 11:16 pm

    Chickens do have genes for teeth. They were just inactivated.

    http://www.ncbi.nlm.nih.gov/pubmed/20403965

    SARA, a possibility might be DNA splashed out of the Earth’s atmosphere and preserved at the lunar poles where it is ~40 K. Of course it is probably pretty iffy if there is any there, and finding it if it is there would be difficult as would the reconstruction.

  13. ChrisHon 05 Jul 2012 at 11:30 pm

    On the question on whether the chicken or the egg came first, we can now with confidence say that the egg came first. Of course it was a dinosaur egg.

    Oddly, I am having flashbacks to playground debates about this from when I was a kid many many decades ago (okay, the 1960s in Ft. Ord, CA, not far where the Mythbusters do their driving through abandoned neighborhood bits). Learning that chickens descended from a dinosaur is really cool.

  14. nybgruson 05 Jul 2012 at 11:40 pm

    D2u: -40K? Methinks a typo is afoot

  15. eiskrystalon 06 Jul 2012 at 3:56 am

    …then just a regular dinosaur, then just a regular bird. They also argued that, whatever it is, there is no proof that it is actually transitional between dinosaurs and birds

    There’s your creationist fail. Right there.

  16. Kawarthajonon 06 Jul 2012 at 8:50 am

    It is amazing to me that dinosaurs with feathers or proto-feathers are so common, and yet we have only begun to realize this in the last few years. Is this because most of these feathered dinos lived in what is now China? Or other parts of the world that hadn’t been well searched for dino bones?

    What a great story. Just when scientists think they know a lot about a subject, new discoveries dramatically change the way they think about things. The fact that dinos had feather-like stuff on their skin probably lends evidence to the fact that they were warm blooded, does it not?

  17. quarksparrowon 06 Jul 2012 at 1:46 pm

    @elmer mccurdy: Beaks are much lighter than jaws with teeth (keratin vs bone), so even to a predatory bird, it’s advantageous to be toothless.

    Though as it is, there’s evidence that birds have lost the genes required to produce functional teeth: http://www.biomedcentral.com/1471-2148/8/246/

  18. jreon 06 Jul 2012 at 4:29 pm

    … a typo is afoot …

    A pity, since with that number he could have hit C or F.

  19. BillyJoe7on 08 Jul 2012 at 3:04 am

    Of course this just means that the scientists were wrong once again. First dinosaurs didn’t have feathers, now they do. First birds were in a group of their own, now they are in with the dinosaurs. When will they ever make up their minds.
    Meanwhile the bible has all the answers. And the answers never change.

  20. eiskrystalon 09 Jul 2012 at 4:17 am

    Meanwhile the bible has all the answers. And the answers never change.

    According to the Bible, which mobile phone should I buy?

  21. BillyJoe7on 09 Jul 2012 at 6:56 am

    The bible is silent on mobile phones.

  22. eiskrystalon 09 Jul 2012 at 10:55 am

    Shame. Well, that’s always going to be a problem with non-temporal concepts within a temporal universe.

    Can it tell me then why pi is 3.14? That should be an obvious one to come up in a book about the universe given the number of times that pi appears in other formulae in most branches of science.

  23. nybgruson 09 Jul 2012 at 2:28 pm

    Actually, according to the bible, pi=3

    Granted it isn’t a direct statement on pi, but the circle they describe would require pi=3 for the measurements described.

    But of course, many attempts to salvage this are made, including the most “reasonable” one by the ICR which attempts to explain it as a factor of significant figures which would allow the description to encompass pi=3.14… Of course that isn’t enough, so they go on to say how obvious such an interpretation would be thus preserving the infallibility of the bible and ensuring that “the Bible is not only correct, it foreshadows modern engineering truth.”

  24. eeanon 10 Jul 2012 at 11:14 am

    Steven, you are ignoring the ‘obvious’ argument creationists can make now: dinosaurs are just type of bird. :D

    Creationists do seem to spend a lot of time talking about dinosaurs, I guess because they capture the public’s imagination so vividly. So I suppose creationists might have a hard time explaining that chickens are just a subspecies of T-rex, since that’s just so obviously wrong, but that might not stop them from trying…

  25. AttacusAtlason 18 Jul 2012 at 11:55 am

    Dr. Novella — TYPO in first sentence of last paragraph. Should read “the group hypothesized to BE related”.

  26. Dfoxman1959on 24 Jul 2012 at 9:31 am

    I have a very interesting story play out when I was in third grade. I was a fanatic about dinosaurs and knew more about them then the teachers. As such I was invited to help narrate a slide strip (this dates me!) along with two 5th grade boys in front of some 1st graders. One of them asked, “Did dinosaurs live during humans?”. Having read a couple of books, I said, “No” when both 5th graders said, “Yes they did!” We proceeded to argue for a few minutes until the teacher told us to quiet down. At that point one of the slides had a picture showing a caveman throwing a rock at a dinosaur! The two 5th graders looked at me and said, “See! We told you so!”

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