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Re: Long Bone Scaling in Neosauropod Dinosaurs

The interpretation seems to be that large animals simply move much more
carefully than smaller ones: they don't need to be athletic since they
don't need to deal with all that dangerous messing about with predator
avoidance that constrains smaller animals.  Likewise, perhaps, with
sauropods (despite that fascinating thread a few months ago about big
theropods attacking their necks).

Even with predation, large animals have multiple 'methods' for mediating the stresses on long bones, such that they can be more gracile than expected under isometry. The manner in which the limbs are held changes with size, for example (which McN. Alexander has noted, as have several other comparative biomechanists). Since bone is usually stronger under axial compression than bending or torsion, straightening the limbs reduce the bone strength required to maintain a given safety factor relative to maximum loads. There are also often changes in gait, which large animals can get away with because of longer strides (and perhaps a lessened need for rapid speed, at the very largest sizes). Such 'gait shifting' actually seems to play a role in other forms of locomotion, as well, though the relevant kinematics are obviously different.


--Mike H.