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Re: Dilophosaurus Forelimb Bone Maladies
Note that the _Cathetosaurus_ in question was probably nowhere close to
20t. Jensen himself described it as a small sauropod no more than 10-15t
in weight, and that’s from a paper (and a time) full of sauropod mass
estimates that are excessive from a modern point of view (such as 80t
Sadly Jensen really doesn’t seem to give any measurements of the
material that could be used to confirm its size (though there is an
osteological monograph that I don’t have access to which probably
does…so if anyone has better data on this, they’d be appreciated), but
it’s a good guess that this sauropod individual wasn’t much more than
elephant-sized when it died.
Also the attacking theropod was implied to have been quite large,
_Torvosaurus_ or "fragmentary large allosaur"-size, so 3t is more like it.
In the end I think the sauropod here is probably 2-3 times the size of
its purported attacker, not 10 times.
It’s a common strategy among animals that kill large prey, at least
those with a sharp, polyphyodont dentition, to disable some part of the
locomotive system. Great white sharks bite the caudal peduncle when they
take sizeable cetaceans (Long & Jones 1996), and they reportedly employ
a similar methods against elephant seals. Komodo dragons sever the leg
tendons of everything from deer to water buffalo and then finish it off
(there is ample camera footage of this, but it also contains ample
amounts of deer getting their intestines torn out while still alive, so
consider yourselves warned).
In this case though, the bite marks are on the pelvis. The hindlimbs
weren’t found though, so that doesn’t necessarily preclude a
But given that Jensen’s hypothesis is correct (and I’m not saying it
must be, but I do not disagree with his premise that a large Jurassic
theropod could have successfully attacked and killed the sauropod in
question), there’s another possibility, which is a deep bite to the
pelvic musculature, both providing immediate nutrition in a possible
'flesh-grazing' scenario (equivalent to raptorial delphinids or
accipitrids), and causing significant functional impairment and
Allosaurids seem equipped for both these scenarios, with dorsoventrally
strong but lightweight skulls and a cervical musculature and flexible
neck capable of both quick strikes and powerful head-depression to carve
deeply into flesh (Bakker 1998, Rayfield 2001, Snively et al. 2013).
So I doubt think a would-be brontophage would have to rely on pure
chance to bring down a sauropod.
Bakker, Robert T. (1998): Brontosaur killers: Late Jurassic
allosaurids as sabre-tooth cat analogues. Gaia, 15 pp. 145-158.
Long, Douglas J.; Jones, Robert E. (1996): White Shark Predation and
Scavenging on Cetaceans in the Eastern North Pacific Ocean. In: Klimley,
Peter A.; Ainley, David G.: Great White Sharks: the biology of
Carcharodon carcharias. San Diego, pp. 293-307.
Rayfield, Emily J.; Norman, David B.; Horner, Celeste C.; Horner,
John R.; Smith, Paula M.; Thomason, Jeffrey J.; Upchurch, Paul (2001):
Cranial design and function in a large theropod dinosaur. Nature, 409
(6823) pp. 1033-1037.
Snively, Eric; Cotton, John R.; Ridgely, Ryan; Witmer, Lawrence M.
(2013): Multibody dynamics model of head and neck function in Allosaurus
(Dinosauria, Theropoda). Palaeontologia Electronica, 16 (2) pp. 1-29.
On 03.03.2016 23:39, Dann Pigdon wrote:
On Fri, Mar 4th, 2016 at 5:56 AM, Mike Habib <email@example.com> wrote:
A two ton predator would have to be suicidal to take on a 20 ton animal.
That depends on what you mean by 'take on'. A direct assault on a healthy
animal is unlikely to
succeed, but a loud and ferocious bluff might be enough to panic a sauropod
into stumbling and
injuring itself, turning it's own mass against it.
A sauropod with a severely injured leg is unlikely to survive for long,
especially if it's left lying on its
side and unable to right itself, leading to the sort of complications that
large beached whales fall prey
to (breathing difficulties, internal injuries). Even a sauropod with a slight
limp may be doomed if it
can't forage effectively enough. It would require a very patient predator to
follow it around until it was
too weak to effectively fight back though.
I often wonder whether sauropods ever dared to drink water directly from rivers
or waterbodies, given
the size of some of the crocodilians about during the Mesozoic. A drinking
sauropod would seem to
present an easily killed target if it presented its head in a convenient
position to be swiftly
decapitated. Perhaps there's a reason why we find so many headless sauropod