Michaelangelo’s weapon of choice or exceeding 344 m/s by way of a flagellicaudatan appendage
February 7, 2008
Compared to what you’re used to, this photo is undeniably crappy. But it’s the only one I have to hand of something really quite interesting: the distal ‘whiplash’ part of the diplodocid tail. This whiplash belongs, of course, to the (remounted) Diplodocus carnegii cast displayed at the Natural History Museum in London (photo © NHM): as is well known among dinosaur aficionados, this is one of the eight copies made of the Carnegie Museum of Natural History composite specimen CM84* and distributed by Andrew Carnegie and W. J. Holland around the world. Casts of the Pittsburgh composite were also sent to Paris, Berlin, Vienna, St. Petersburg, Mexico City, and La Plata. One was also sent to Munich, but never got mounted.
* The specimen is sometimes called just CM84, but in fact also bears the specimen numbers CM94 and CM307 for various of its parts.
Several workers have popularized the idea that the distal ‘whiplash’ part of the diplodocid tail functioned in defence, the diplodocids flicking their immense tails to throw the thin, whip-like distal part towards an attacking theropod. Ever one to appeal to popular culture to help get his message across, Robert Bakker (1994) argued that the loss of muscles, nerves and joint prongs (=zygapophyses) on diplodocid whiplash caudals made them into an ideal ‘multijointed numchuck: a dinosaurian version of the weapon favoured by Michaelangelo of the Teenage Mutant Ninja Turtles’ (p. 33). Because the tail-tip consisted of simple rods connected on all sides by tendons, said Bakker, the whiplash would be unbreakable, and a diplodocid ‘could whack away at an allosaur to its heart’s content without worrying about tail-bone breakage’ (p. 33) [hilarious image below, from here. Can be enlarged by the wonder of mouse-clicking].
Alas, Per Christiansen (1996) challenged this idea, arguing that the general similarity present between the distal caudal vertebrae of diplodocids and those of other sauropods indicated the lack of any ‘special function’, that the fusion sometimes seen in diplodocid distal caudals was at odds with the idea of a whip-like function for the tail tip, and that diplodocids did not have tail musculature powerful enough to swing the tail in whip-like fashion. In strong contrast to what Bakker said, Per also argued that the small, thin distal caudals were unlikely to be strong enough to fend off an aggressive theropod, and he even suggested that the distal part of the tail might ‘simply come apart if striking another object with this amount of force’ (p. 56).
Myhrvold & Currie (1997) also noted that the whiplash ‘was not well adapted as a direct-impact weapon’ (p. 393), and they gave similar reasons to those provided by Christiansen. But they also suggested that the tail-tip could perhaps be moved fast enough to generate a loud noise, and computer modelling suggested that the tail-tip could be moved at 540 m/s, fast enough to generate a supersonic crack (the speed of sound is 344 m/s). This noise might, they speculated, be a deterrent to big predators, especially those with sensitive hearing (Myhrvold & Currie further speculated that diplodocids might have communicated over distance using loud tail cracks).
As always, there’s a lot more you could say about this subject, but it’s 2-30 am and I would like to get some sleep. Until next time!
References
- Bakker, R. T. 1994. The bite of the bronto. Earth 3 (6), 26-35.
- Christiansen, P. 1996. The “whiplash” tail of diplodocid sauropods: Was it really a weapon? In Morales, M. (ed.) The Continental Jurassic. Museum of Northern Arizona Bulletin 60, pp. 51-58.
- Myhrvold, N. P. & Currie, P. J. 1997. Supersonic sauropods? Tail dynamics in the diplodocids. Paleobiology 23, 393-409.
Sauropod Vertebra Picture of the Week 
February 7, 2008 at 9:21 am
I look at the tail’s mobility and very large surface area to volume ratio, and it makes me think about cooling. Is there any hint that there was more blood flow in the tail than would reasonably be needed otherwise?
February 7, 2008 at 3:35 pm
A copy of the Pittsburgh composite Diplodocus is also in Bologna (Italy).
February 8, 2008 at 12:31 am
I’ve heard often of the supersonic idea. Is that notion…accepted? I kind of liked the idea posited in Walking with Dinosaurs (one of the few) in which the tails were banded and brightly colored and served as signaling and communication devices between members of the herd.
February 8, 2008 at 2:36 pm
Hi all. More blood flow in the tail than otherwise needed? Nope, no evidence for that (but, not much evidence on the finer details of circulation in sauropods anyway!). My suspicion is that the tail would have had the same function in shedding heat as any other appendage, and I can’t think of any evidence suggesting that it had a special role.
Supersonic notion is not – so far as I know – accepted as ‘for sure’, but it’s conceivable. I’m on the fence on this one. And maybe the tails were hazard-striped, maybe not, but I agree that it looks neat. Incidentally, WWD made the whiplashes way, way too flexible.
February 10, 2008 at 11:29 pm
Okay, so I haven’t read TFP, but are Per’s comments based on any sort of quantitative analysis, or are they more of an eyeballed guess? I mean to say, I guess they have as much validity as Bakkers’s eyeballed guesses, but until we have some actual qualitative data on this, it all seems like arm-waving.
I confess to liking the idea myself, and club-tailed sauropods do seem to lend some weight to the notion.
February 12, 2008 at 3:01 am
Hi John. I don’t have the paper beside me now (I’m writing from the side of my swimming pool, martini in [left] hand), but – yeah – Per’s evaluation is subjective and based on the ‘look’ of the vertebrae so far as I recall.
Did you believe the bit about swimming pools and martinis? Please say yes :)
February 13, 2008 at 4:46 am
A predator bothering a creature that could make its annoyance known for miles around would find its next meal a long, long walk away.
March 6, 2008 at 2:49 am
Hi, does the flexibility increase noticeably near the tip or not? I am wondering if the whipcrack idea may depend crucially on a very quick-flicky-tricky* end that could effectively double back on itself to make the crack, or at least flex awesomely fast and free (feel free to adopt that* as a technical term BTW, cf ‘Thagomizer’);-) (remember, you saw it here first).
But hey – (quickly second-guessing myself) – do we even know where the fleshy tip was relative to the bony tip? Could there have been a boneless whip-flip-tip?
Alternative hypothesis: sauropod tails had nested rings hardened remnants of successive skin-sheddings: a mega-Rattlesnake-rattle.
(Feel free to cite me. Pleease!!)
Now, someone do a scaled decibel estimate…
April 29, 2008 at 9:35 am
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June 9, 2008 at 9:29 am
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January 2, 2009 at 4:43 pm
I wonder if anybody calculated the strengh of tearing forces when sauropod tail is moved at supersonic speed?
My guess is that skin, blood vessels and tendons would tear apart long before the speed reached supersonic values. Any evidence of loose tailtips of diplodocids hanging from branches of Mesosoic trees?
The better idea (AFAIK not yet suggested) is that tail tip would be sensitive, movable touching organ used when sauropod tended its relatively diminutive eggs and juveniles. I think there is now some evidence that sauropod nests were cared for and juveniles stayed with adults, instead of dispersing on their own.
January 2, 2009 at 5:05 pm
Jerzy, remember that SPEED in itself does not generate forces — it’s acceleration that does that. If diplodocids accelerated their tail-tips to supersonic speeds but did so slowly, then I don’t see any reason to think they’d be torn apart.
January 2, 2009 at 5:26 pm
Possum-like prehensile tails? Any cross-comparison studies done on that?
February 18, 2009 at 1:36 am
Even if the tails did not reach supersonic speeds, they certainly would have made a lot of noise.
I still think Bakker’s theory holds in general. Fusion of a few distal caudals does not disprove the whip-defense hypothesis. In fact, it may be a sign of a healed injury related to precisely that use of the tail. Perhaps it was only a pathology. And we have no way of knowing exactly what sort of muscles or tendons were on those bones. A tail whip was probably not fast enough so slice Allosaurs in half like that hilarious little drawing… But it would certainly cause bruising and wounds and act as a deterrent.
All Jurassic dinosaurs needed some sort of deterrent – you had bigger predators than before – Allosaurs, Megalosaurs, Ceratosaurs, Sinraptorids… they were everywhere. So Diplodocids had the tail whip. Stegosaurs had spikes. Brachiosaurs were just plain HUGE. And early Ornithopods – well, lacking any sort of physical defenses, they RAN!
And of course, Euhelopodids seem to combine the traits of Brachiosaurs and Diplodocids (without either one’s real strong points – their tails are not that long, and they only have a Height advantage over some Brachiosaurs – not a MASS advantage), and they also have monstrous thumb claws. Each group had one main defense.
May 24, 2009 at 3:36 am
What kind of person calls nunchakus ”numchucks”?
May 26, 2009 at 9:16 am
Err.. Robert Bakker?
April 6, 2011 at 10:24 pm
[…] And of course this never-to-be-forgotten classic by our own Darren Naish (previously featured here): […]
September 8, 2016 at 8:45 am
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