Apr 05 2012

A Feathered Tyrannosauroid

Yet another feathered dinosaur has been discovered in China – this one is a relative of T. rex and is the largest creature with feathers, extant or extinct, to have been discovered. Yutyrannus lived about 125 million years ago and is an early cousin of the T. rex.

This is one of my favorite paleontological stories – in fact, it’s one of my favorite science stories because it demonstrates one of the ways in which evolution is testable. When Darwin first proposed his theory the fossil record was very scant. Further, the number of species currently alive is a very small portion of the number of species to have ever lived (scientists are fond of saying that most species to have ever lived are extinct).

This means that when we look at living things in order to infer the relationships among them, different plants and animals might appear to cluster in separate groups. Actually a thorough survey of living things shows a pattern of nestled categories that are blurry at the edges (I’m looking at you, platypus) and nicely reflects a branching pattern of common descent. But still, there do appear to be distinct groups. This appearance, however, is an artifact of the incompleteness of the sample of all living things represented by those species that are still alive.

Birds are a classic example. Birds appear to be a very distinct group with features (i.e. feathers) shared by all birds but absent in all non-birds. “Aha,” said creationists at the time The Origin of Species was published, “there are no connections between major groups and if evolution were true then we would expect to find connections all over the place.” In fact some creationists still say this today, but now they have a growing body of evidence to deny.

This challenge to evolution created an excellent opportunity to test the theory that all life on earth is related through common descent with modification. If evolution were true, and we are just missing a lot of pieces to the puzzle of life on earth, then we would expect to find fossil evidence of extinct species that fill in the gaps between living groups. If evolution were not true, and the different “kinds” of life were all separate creations, then we would not expect to find fossils which fill in the gaps (beyond some chance correlations).

In 1861, just two years after On the Origin of Species was published, the Berlin Specimen of Archaeopteryx lithographica was announced. This is a specimen of an early bird, complete with modern-looking feathers. The specimen also displays many primitive features that are reptilian, in fact that are very similar to theropod dinosaurs. Archaeopteryx, in short, is a beautiful transitional fossil between two major groups – birds and dinosaurs. It is half bird, half dinosaur. Really, it doesn’t get better than this (although there are many other examples of stunning connections between major groups). Archaeopteryx was taken, rightly, as confirmation of Darwin’s new theory – at least by the scientific community.

Creationists, however, stubbornly ignored the implications of this fossil and variously dismissed it as a hoax (it’s not) or as just a weird bird with teeth and a bony tail. Other specimens of Archaeopteryx have been found over the years, many beautifully preserved with feather impressions. But for a long time it was isolated as the only fossil connection between birds and dinosaurs. Over that same time, the century following Darwin, evolutionary theory became much more fleshed out, as did the fossil record. We began to appreciate that evolution is a complex branching bush (rather than a ladder or a linear progression), and that successful species tend to experience adaptive radiation, filling the environment with variations on basic morphological themes.

Then in the 1980s paleontologists hit pay dirt in China, discovering fossil beds with other feathered dinosaurs. Over the last three decades they have continued to find more and more feathered dinosaurs, and evidence that known dinosaurs (like velociraptor) had primitive plumage. They found primitive feathers that were not used for flight, dinosaurs with all four limbs adapted for flight, and everything in between. Now we have a whole host of feathered dinosaur specimens at the correct time in geological history, clustered in one region of the world. This is exactly the kind of thing that evolutionary theory predicts should be the case – wide distribution of an adaptation, one branch of which led to flight and early birds. The fossils also show that feathers themselves had ancestors that were clearly not adapted for flight, and so served other functions.

I can’t help feeling that every new feathered dinosaur discovery is like a dagger straight into the heart of creationist denialism of evolution. I have to wonder if it makes them squirm, even just a little. Probably not, the power of rationalization is just too great, but it’s fun to think about.

With this latest discovery we have more evidence that feathers were a common adaptation in this branch of the dinosaur order, even existing on some of the big boys – the tyrannosauroids. This specimen also adds to the debate over whether or not T. rex had feathers. Given how common feathers were in this group, the answer is that T. rex probably did sport some sort of plumage. It’s possible that just the young ones had downy feathers to keep warm, but adult T. rex did not have any feathers. It is also possible adults had feathers for display or some other purpose. The discovery of yutyrannus makes it more plausible and likely that even adult T. rex had feathers. We cannot know for sure until we find a T. rex specimen preserved in such a way that feather impressions would be visible. That would be an exciting find.

Meanwhile, I can enjoy the latest feathered dinosaur discovery, and welcome yutyrannus as the largest member of this group (pending definitive data on whether or not T. rex had feathers).


11 responses so far

11 thoughts on “A Feathered Tyrannosauroid”

  1. SARA says:

    I continue to wish the premise of Jurassic Park would come true. Or that there was some preserving agent like the ice with wooly mammoths or the amber with insects that would show us a fleshed out dinosaur specimen.

    Not that this would convince the creationist who would undoubtedly take a page from the moon hoaxers etal and begin calling it a hoax, but it would AWESOME for the majority of the world.

  2. vanderleun says:

    I’m so disappointed you didn’t use this opportunity to title it: “Love is the Tyrannosauroid with feathers.”

  3. kikyo says:

    I am in love with these dinosaurs. I know in reality they were gigantic and scary, but in the picture they look so … adorable.

  4. jre says:

    In Willy Ley’s excellent Exotic Zoology, there is a boyhood reminiscence of visiting the Berlin museum where the eponymous specimen was housed — at that time in a dark, dusty back room, mixed in with the other fossils. Even without any signs to flag its importance for him, young Willy knew this bird was magical.

    I particularly like your point about how fossil discoveries continue to vindicate Darwin. Whenever multiple independent lines of evidence tend to support the same theory, and especially when the evidence becomes stronger with every new discovery, scientists are justified in calling that theory robust — no matter what they call it in Tennessee.

  5. Jared Olsen says:

    Beautiful plumage…

  6. BillyJoe7 says:

    “most species to have ever lived are extinct”

    I have read in various places that the figure is 99% (some even claim 99.9%)
    Does anyone know if this figure is correct?


    BTW, the full name for this therapod dinosaur is:
    Yutyrannus huali
    “Yu” is Mandarin for “feathers”, “tyrannus” is Latin for “king”, “huali” is Mandarin for “beautiful”.
    The beautiful feathered king

  7. etatro says:

    @BillyJoe7: I think given that life has been around for 3.8 billion years and that all current species are descendent of extinct species and that we know there are many, many, countless species that went extinct that have no descendants, I kind of think that anyone who puts an actual percentage to that “most” is blowing smoke. Probably well meaning to indicate “a whole heckuva lot,” but I wouldn’t believe any figure without some evidence (which might exist but I haven’t read it). I kind of think there isn’t enough space in this text field to put all the 99.99999…’s to come up with a number that would not actually round up to 100. I might be wrong, of course. In fact, I think a paper that deduces this figure would be an interesting read.

    @Rikki-Tikki-Tavi: I think that the hypothesis that T Rex had feathers is falsifiable. Finding a preserved T Rex specimen with skin in-tact with no feathers would falsify it. Genetics might work too. If we sequenced all the known to be feathered dinosaurs (particularly closely related to T Rex) and found a sequence or gene that all feathered’s had but no non-feathereds had, which T. Rex also lacked, would be strong evidence against T. Rex having feathers. Those’re a few ideas. Probably others.

  8. BillyJoe7 says:

    Rikki-Tikki-Tavi: “Tyrannus, I think, means tyrant. Rex means king.”

    You are correct.
    I will take the correction back to my source (Jerry Coyne!)

    etatro: “I kind of think that anyone who puts an actual percentage to that “most” is blowing smoke….I kind of think there isn’t enough space in this text field to put all the 99.99999…’s to come up with a number that would not actually round up to 100.”

    Could we agree, then – without putting an actual figure on it – that it is at least 99.9%

  9. DS1000 says:

    @ Rikki-Tikki-Tavi, per your question about falsifiability. I think maybe your confusing the concept that it’s impossible to prove a negative with the idea of unfalsifiability. Like etatro said, there are several ways to test that T-Rex had feathers, regardless of whether you frame the hypothesis in the positive or the negative. If we never find evidence that it had feathers, that would be ok; we’ll simply stick to the conclusion that it probably didn’t have feathers until we find out proven otherwise.

    The idea of an unfalsifiable hypothesis is that it is unfalsifiable in principle. An example of an unfalsifiable hypothesis is that the T Rex had a special kind of feathers that by their nature leave absolutely no evidence in the ground, and there are no other methods that can ever exist to find out about them

  10. Mlema says:

    “I can’t help feeling that every new feathered dinosaur discovery is like a dagger straight into the heart of creationist denialism of evolution. I have to wonder if it makes them squirm, even just a little. Probably not, the power of rationalization is just too great, but it’s fun to think about.”

    “Whoever fights monsters should see to it that in the process he does not become a monster….”

    — Friedrich Wilhelm Nietzsche

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