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Thursday, September 15, 2011
Running around like an Ornitholestes with it's head cut off!
If you watched Episode II of Dinosaur Revolution, you may have laughed at this Ornitholetes, who I'll refer to as Ichabod. This may seem like an odd scene to pick for a scientific discussion, but I think it actually has something useful to teach. Also, I'm partially responsible. I should be clear, the story idea was not mine (that's above my pay grade), but it's something that was run by me, and I did not try to shoot it down (and still wouldn't).
Why? I think it's reasonable.
No wait, let me explain: I'll grant you that there isn't much in the professional literature on the subject on the subject of "headless running" in animals, but from some criticisms I've read I think people maybe thinking about this the wrong way (i.e., wondering about the distribution of "headless-running" in birds like the behavior it's an advanced condition).
Vertebrates as a group have one of the more centralized nervous systems among animals (with some arthropods and especially some cephalopods as the other contestants in the "flexibility over redundancy sweepstakes"), but tetrapod nervous system evolution in general is a story of progressive centralization that (so far) culminates in mammals. Even in humans, with our gobs of ridiculously calorie-hungry centralized gray matter, we still have autonomous reactions that don't require the brain to be involved (as anyone knows who's burned themselves and jerked their hand away before they felt the pain). That said, we have gone a long way down the path of nervous system centralization, and if you cut a mammal's head off you may get some twitching but it won't run around; our limbs literally cannot coordinate themselves without the brain's involvement (although morbidly it does appear that the head itself retains some coordination afterwards, if medieval reports are true that heads react for up to a 15 seconds after a beheading).
This degree of centralization is the derived condition, not the primitive one. So it seems unlikely that chickens are special here, except in as much as they more frequently get clean beheadings in the presence of human observers than most other birds (a quick Google search shows that turkey's exhibit this as well). This should be true of lizards, crocs, etc too (diapsids as a whole). So with enough experimental trials I'd fully expect an Ornnitholestes to do a good headless chicken impression. Now, I'll grant you that this would require a pretty clean bite on the allosaur's part, and the odds of observing it in the wild would not be very high. But the sequence was devised as be a surprising bit of humor in a scenario that was possible, not probable.
Given those parameters it seems reasonable enough to me.
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I have seen snakes wriggle several hours after skinning and beheading. I guess you're on to something ;)
ReplyDeleteCurious if this is a case where "mammals" actually means "mammals" or if it means "therians" or "placentals" instead.
ReplyDeleteThat's an excellent question Mike. I haven't personally looked at what literature there is on say monotreme brains, so I don't really know. I'll see what I can come up with.
ReplyDeleteMaybe relevant? http://www.dwc.knaw.nl/DL/publications/PU00013831.pdf
ReplyDeleteThe Roman emperor Commodus is supposed to have decapitated ostriches for fun, which then continued to run about headless. No idea whether this has any truth to it or not, but if so it makes the Ornitholestes scene that much more plausible.
ReplyDeleteJust read this and had to smirk at the thought that - just maybe - [i]Elaphrosaurus bambergi[/i] had kept someone up all night:
ReplyDelete"In late 1925... the second Tendaguru doinosaur was mounted and placed on public display (...) It was felt that a headless mount would appear unfinished so Janensch so [the skull and lower jaws were produced entirely in plaster.] He admitted that the model was bereft of any scientific value."
African Dinosaurs Unearthed, Gerhard Meier; pp. 196-7
@Niel: I would expect Ostriches to also do this - do you happen to have a source for the historical claim? That would be a fun addition to the "odd and interesting tidbits" part of my library.
ReplyDelete@David Maas: That would be really funnny. Elaphrosaurus is on my "medium-list" of dinosaurs I have all the info ready for a skeletal and _really_ want to do one for, but keeps getting pushed back due to the needs of myself or others. Maybe in early 2012...
Looks like it can be trace back to Herodian (ca. 170-240):
ReplyDelete"Commodus decapitated the birds at the top of their necks with his arrows, so that they went on running around as though they had not been touched, even when their heads had been cut off by the sweep of an arrow"
I've been trying to write a species of sapient, civilised dromaeosaurs, and I've been wondering how /they'd/ react to decapitation. Does the ability to make art and use fancy tools necessarily imply a more centralised nervous system than the average chicken?
ReplyDeleteProbably not - I suspect they'd stay at the same level of motor centralisation and just stuff extra higher functions into the brain. That's going to make public executions interesting!
Hmm, and it'll make spinal injuries a lot less devastating.
Anyone know whether parrots or crows show coordinated locomotion after decapitation?
@Lucy - It's not clear that nervous system centralization has a direct link with intelligence. Sure, mammals currently have the smartest animals, but many living dinosaurs (specifically some parrots) are right up there with the best that non-human mammals have to offer, and crows are known to make and use tools.
ReplyDeleteNow a good question is whether there is any progression in terms of nervous system centralization in those bird lineages. If not, then centralization must occur for other reason in the mammalian lineage.
It's a question that could really benefit from more data, but to answer your specific question, I don't see a reason at this time to assume that an imagined lineage of intelligent dromaeosaurs would have to adopt a more centralized nervous system.
Sorry for the late reply but I think 'plausible' and 'reasonable' are two different things.
ReplyDeletePaul W.
@Paul - Fair enough. But if people are honest with themselves they should admit that many documentaries have been made showing uncommon behaviors. And in this case the show was not originally intended to be a documentary in the traditional sense (although unfortunately it ended up being marketed that way).
ReplyDeleteermmm.. I don't know about "mediaeval", but Lavoisier, the discoverer of Oxygen, was a scientist to the end. Condemned to death by the French reign of Terror, he arranged for a friend to count the number of times he blinked after he was guillotined.... and swore he would die trying to blink at regular intervals. it is said he blinked seven times at intervals of a bit over one second.
ReplyDeleteWhat a mensch!!