Monday, February 28, 2011

Singing "Raptors"



Though that doesn't explain why Skull (and everyone else, for that matter) can talk. Not to mention we've seen him sing before. Go figure.

For a while, the answer to "Could dinosaurs vocalize?" was, "Sure, why not?" After all, both living dinosaurs (neornithines) and their closest living relatives (crocodilians) vocalize. But there's a catch. These two groups do not use the same organ for vocalization, meaning they evolved vocalization independently and their latest common ancestor likely couldn't vocalize at all! In crocodilians, vocal sounds are made by the larynx, while birds have an organ called the syrinx. We don't know how when crurotarsans evolved their larynx, because there are no skeletal features that correspond to this organ. However, there is a way to tell if a syrinx is present in extinct archosaurs, and that is the presence of the clavicular air sac that is required for the syrinx to function. As it turns out, although all saurischians have air sacs, only ornithothoracines (enantiornithines, hesperornithines, yanornithiforms, neornithines, and some intermediate taxa) have the clavicular air sac. (The carnosaur Aerosteon had a clavicular air sac, but this was likely evolved independently of the one ornithothoracines have.) That means non-ornithothoracine dinosaurs did not possess a syrinx and were probably not able to make vocal sounds. In fact, this might help explain why so many different dinosaur groups evolved so many different visual display structures.

Fans of roaring tyrannosaurids, screaming deinonychosaurs, and groaning sauropods, your childhood has just been ruined forever. But don't despair, as there are other means for non-ornithothoracine dinosaurs to have communicated acoustically. Mechanical ways of sound making such as foot stomping, wing beating, jaw snapping, hissing, and splashing are certainly not out of the question. And the traditional idea of trumpeting hadrosaurs may still be safe; you don't need vocal chords to blow a musical instrument, fortunately.

Nonetheless, I don't think we'll be seeing non-roaring tyrannosaurids on screen anytime soon. Reality is unrealistic. Thank the coconut effect.

Edit: See comments (and addendum).

14 comments:

  1. Now, I'm a bit confused here. If Aerosteon had a clavicular air sac, albeit convergently, shouldn't it also be able to vocalize in a similar manner as modern birds?

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  2. Having a clavicular air sac doesn't mean you have a syrinx. There's no reason to assume that Aerosteon also convergently evolved a syrinx along with its clavicular air sac.

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  3. so did dinosaurs not make vocal sounds at all?

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  4. That appears to be the case. (Ornithothoracines could and can, but even basal avialians lack evidence for a clavicular air sac.)

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  5. they could still beat-box though, right?

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  6. I think there's been a mistake here, and that the claims of 'no laryngeal involvement in avian vocalisation' are based on old literature. Not only do birds possess a larynx, recent work has shown that (in some species, like chickens) it is highly mobile, and that it does indeed play a role in vocalising. I'll have a chat with Phil Senter about this some time (he's the one responsible for the argument you report above).

    See...

    Homberger, D. G. 1986. The lingual apparatus of the African grey parrot Psittacus erithacusLinné (Aves: Psittacidae): description and theoretical mechanical analysis. Ornithological Monographs 39, 1-233.

    - . 1999. The avian tongue and larynx: multiple functions in nutrition and vocalization. In Adams, N. & Slotow, R. (eds) Proceedings of the 22nd International Ornithological Congress,University of Natal, Durban, South Africa. BirdLife (Johannesburg), pp. 94-113.

    And some of this was covered on Tet Zoo (though I can't provide a link right now, as the whole of ScienceBlogs is currently inaccessible to me).

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  7. OMG OMG OMG Dr. Darren Naish commented on my blog!!1!!!1!!1!1!eleventyone!1!

    Thanks for the info! I'll be sure to make an addendum.

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  8. I now love Naish more than I did before (and that's saying something)!

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  9. Is howling a vocal sound?

    Oh, and it turns out T.rex WAS a silent killer. >:D

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  10. Yes, I think howling is generally vocal.

    Haha! See the addendum though. ;)

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  11. But wouldn't hissing also be considered vocal?

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    1. Hissing is just forceful blowing of air, so it doesn't require a specialized organ for vocalization.

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  12. In the whatchacallit-saurus that DID have the clavicular air sac, what purpose could it have if not to support vocalization of some kind? Please excuse my ignorance.

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    Replies
    1. Air sacs primarily function in respiration. They are also used for thermoregulation.

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