How long have we known that dinosaurs were birds?


I spent most of my childhood with books about dinosaurs that played up the ancient beasties as overgrown lizards. The connection between dinosaurs and birds, while kind of flipping obvious once somebody points it out, was not much discussed among laypeople until I was in my teens. (That would be the 1990s, FYI.) 

But, among scientists, the idea of a dinosaur-bird relationship is nothing new. In fact, Thomas Henry Huxley was making that connection back in the 1860s. On the Dinosaur Tracking blog, Brian Switek tells the fascinating story of how Huxley started to realize that dinosaurs and birds were related—a discovery that's all the more impressive because he figured it out without the help of some of the key transitional fossils we have access to today.

Huxley did not suggest that birds were the direct descendants of dinosaurs. So much geologic time was unaccounted for, and so few dinosaurs were known, that Huxley could not point to any known fossil creature as the forerunner of birds. Instead he made his argument on anatomical grounds and removed the issue of time. Dinosaurs were proxies for what the actual bird ancestor would have been like, and flightless birds (such as the ostrich and emu) stood in for what Huxley thought was the most archaic bird type. (We now know that Huxley got this backwards—the earliest birds could fly, and flightless birds represent a secondary loss of that ability.) As Huxley went about collecting evidence for his case, though, he also gave dinosaurs an overhaul. They were not the bloated, plodding, rhinoceros-like creatures that Richard Owen had envisioned. Dinosaurs were more bird-like than anyone had imagined.

In October of 1867, Huxley met with John Philips, an English geologist and a curator of Oxford’s museum. As Huxley related in his 1870 paper “Further Evidence of the Affinity Between the Dinosaurian Reptiles and Birds,” Philips wanted to discuss details of marine reptiles called ichthyosaurs in his museum’s collection, but as he and Huxley made their way over toward the displays they stopped to look at the bones of the carnivorous dinosaur Megalosaurus. Then Huxley spotted something peculiar:

As Prof. Phillips directed my attention to one after the other of the precious relics, my eye was suddenly caught by what I had never before seen, namely, the complete pectoral arch of the great reptile, consisting of a scapula and a coracoid ankylosed together. Here was a tangle at once unravelled. The coracoid was totally different from the bone described by Cuvier, and by all subsequent anatomists, under that name. What then was the latter bone? Clearly, if it did not belong to the shoulder-girdle it must form a part of the pelvis; and, in the pelvis, the ilium at once suggested itself as the only possible homologue. Comparison with skeletons of reptiles and of birds, close at hand, showed it to be not only an ilium, but an ilium which, though peculiar in its form and proportions, was eminently ornithic in its chief peculiarities.

Earlier naturalists had made a mistake. They had misidentified the shoulder girdle, and one part of what was thought to be part of the shoulder was actually part of the hip. Another strange piece, previously thought to be a clavicle, also turned out to belong to the pelvis. This rearrangement immediately gave the dinosaur a more bird-like character.

If you look at the bottom of the image at the top of this post, you can see how much the re-arrangement of megalosaurus' parts changed our conception of what the whole creature looked like. Where other scientists saw a lumpy, obese crocodile, Thomas Henry Huxley saw a saber-toothed chicken.

Image: Ballista via CC



  1. Thomas Huxley certainly was a brilliant scientist. And without his work it would have taken much longer before we discovered dinosaurs weren’t sloppy crocs; however, there are still controversies with dino-bird transition.

    There are a few feathered, flying birds that have been found in the same sediment along side dinosaurs. (I’m not talking about the archaeopteryx, either — it’s called the eoconfuciusornis zhengi.^1) The more birds we find along side dinosaurs the trickier it gets to prove the theory.

    There are evolutionary scientists that do not subscribe to the dino to bird theory, too. Like Alan Feduccia world authority on birds from the University of North Carolina at Chapel Hill and paleontologist Larry Martin from University of Kansas.  Also, a study was done back in 2009 (D.E. Quick and J.A. Ruben^2) that find other discrepancies.  While it’s certainly not a earth shattering list it’s not a couple no-names, either.


      1. The offspring from a modern human and a Neanderthal would produce a viable offspring, ergo we are all the same and the same species.  If all the talk I hear about Neanderthals were said about Africans you would be crucified, you are just a temporal racist.  The Neanderthal was fully modern and had complex culture and language — they just looked more macho than you puny city slickers.

        1. you are just a temporal racist

          I’ll have you know that he treats Neanderthals exactly the same as homo sapiens!

          (“temporal racist” has to be the most fucking ridiculous accusation I’ve seen in a while)

    1. What? The more birds we find with dinosaurs, the more support there has been for the theory. Some things traditionally considered non-birds, like dromaeosaurids, are now thought to be possibly flightless descendants of flying ancestors. Chinese finds like Eoconfuciornis are a big part of why there are so few hold-outs against the model.

      Saying theropods lived many millions of years after birds marks a clear confusion about how evolution works. They lived many millions of years earlier, too; those early ones would be the common ancestors of both later theropods and birds.

      As far as the opening post, I’ll second that dinosaurs were not birds. Birds evolved from dinosaurs, as was suggested long ago, and gradually has become more and more clear from evidence.

      I should note, though, that the sudden change to birds are dinosaurs has little to do with this support. It has to do with a new tendency to insist on phylogenetic naming, whereas older authors are happy to split groups based on phenotypic differences. We’ve known humans ultimately evolved from fish for a long time, but it’s only recently anyone would say we are fish.

  2. Erm… shouldn’t it be the other way around, i.e. “How long have we known that birds were dinosaurs”? Because not all dinosaurs are birds ;-)

  3. An interesting effect of the old thunder-lizard mind-set is that there still seem to be more herpetologists than ornithologists in academia.

    Isn’t the key question in the herp – bird controversy which clade is most recently diverged from dinos? Seems like birds are still the most recent ancestor.

  4. I feel like it should be noted that Jurassic Park is likely the sole reason the dinosaur > bird hypothesis finally entered the public eye.

    Clever girl.

  5. Dinosaurs were not birds, they were dinosaurs.  They were all very different – plus we have 0 genetic evidence.  Placental and marsupial mammals are very different, but they both produced tigers that had very similar skeletons.  Your mentality that it is “obvious” that birds and dinosaurs are somehow that same shows your ignorance of the evolutionary sciences and is a reason that evolutionary sciences lack credibility in the public arena — the self appointed spokes people are basically wrong all of the time.

  6. It’s funny. Just the other day, I was talking with my wife about how strange it is that the idea that dinosaurs were warm-blooded still hasn’t entered popular consciousness, despite it being in every book about dinosaurs since the 1980s, except insofar as people have come to know of dinosaurs as the ancestors of birds who are warm-blooded.

  7. I studied palaeontology at the University of Cambridge in the mid-1990s, with some luminary palaeontologists such as Simon Conway-Morris, and if I recall correctly, the dino/bird hypothesis was regarded as a somewhat suspicious theory by some senior people even then.  As a science teacher now I find plenty of the kids know about it before I teach it to them.

  8. I don’t think she meant that dinosaurs are birds in the same sense that birds are dinosaurs. I think she meant that dinosaurs are birds in the sense that, if we wish to understand how dinosaurs lived, thinking of them as some kind of birds is more revealing than thinking of them as some kind of herp, and at least as good as thinking of them as some kind of mammal analogue.

    P.S, in response to chenille, above, but the login system was not working.

  9. in 1977, the zarn character in the original land of the lost saturday morning tv show made some mention about dinosaurs evolving into birds. i was a bit curious and mentioned it to our local librarian who helped me find a “more contemporary” book on paleontology where the “dino / bird” hypothesis was surprisingly well documented.

    fwiw… that show and that experience was part of a chain of events that led me to study science in college (though i’ve been a professional software person for forever.)

    so maybe there were other kids who first heard of the dino / bird connection from classic saturday morning tv.

  10. A lot of great ideas seem obvious in retrospect. I remember hearing the bird/dinosaur thing and feeling that little click in your head that registers the truth of it but I hadn’t seen it for myself.

  11. You seem to be some sort of expert on the subject. Care to share your credentials and references to peer-reviewed papers.

    1. PS, in reply to #mikechappers; the login messed me about. Again. Disqus is bloody awful. It often forgets me and I have to log in again and my reply is no longer relevant to the original post

  12. Any recommendations for kids’ books that tackle this subject? As a sometime elementary school teacher I admit I have never ever made this connection for students, so if there’s a good readaloud book out there I want to hear about it. If not, consider this an opening in the market.

  13. I love seeing the evolution of scientific ideas preserved in the record, it’s like paleontology itself. Thanks for a nice summary of an interesting breakthrough.

  14. “Dinosaurs were birds” is just plain wrong:
    Dinosaurs were birds is not the same as birds were dinosaurs. It’s a bit like saying mammals are whales. One branch of the dinosaur tree did not go extinct, and that branch evolved into modern birds, but to suggest dinosaurs were birds is misleading.

  15. Funny, I felt like this at one point but it seems that the more  I learn about dinosaurs, pterosaurs, and birds – mostly due to the interests of my children – the more it seems that the “dino biz” doesn’t actually think this.  Others said it above here but they are very distinct lines.   Also dinosaurs are still in the class “reptilia”, eh? If the issue had enough support they could be put in “aves” , right?

  16. Maggie, are you not a scientist? If so, how could you frame the title of your post so inaccurately from an evolutionary perspective? X maybe being derived from Y, does NOT mean Y = X, as your title states. This is basic mathematics.

  17. Before Huxley, Amherst College geologist Edward Hitchcock first suggested the dino tracks he found in abundance in Western Massachusetts were made by pre-historic birds. When Sir Richard Owen coined the word “dinosaur,” Hitchcock objected, saying he thought the name misleading–what he saw was more avian than lizard-like. He debated the point with Darwin, too. For more on the man, I wrote a story about Hitchcock a few years back, and his collection of tracks is impressively displayed at the school’s natural museum:

  18. Maggie, do you know about Franz Nopcsa von Felsö-Szilvás’s “pro-avis”?  Baron Nopcsa was talking about warm-blooded dinosaurs evolving into birds in the 1920s.

  19. You know, despite people ragging on Maggie, it’s not that inappropriate to say that dinosaurs are birds. After all, all dinosaurs are stem-birds and part of the Pan-Aves clade (everything closer to birds than to crocodiles), e.g. bird-line archosaurs… :) It’s just a matter of how you want to think about it. When you consider how often people sloppily refer to things outside of the croc clade that were never classically called ‘crocodylians’ as ‘crocs’… I don’t think this is too different or really all that radical.

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