Hello,

Is that true that the cartilaginous skeletons of sharks allow them to reach larger extreme sizes than bony organisms by comparison ?

Thinking about Rhincodon known to have exceeded 12,2 m or C.megalodon which is estimated at 15,6-20,3 m by modern methodology...

Reasons why cartilage is beneficial: http://www.marinebiodiversity.ca/shark/ … /skull.htm

Don't think it has to do with extreme sizes because mammals have bony skeletons and reach large sizes.

Last edited by ReetikaSuri (5th Oct 2012 13:50:23)

Mammals, like other land animals, can't reach their biggest sizes because cartilage is just not stiff enough to support a large body on land. In water, it's another matter: the skeleton doesn't need to work against gravity so its weakness (relative to bone) is not a problem. Note that even sharks ossify the part of their skeleton that has to withstand the greatest stresses -- the jaws.

That said, it's interesting that the biggest ever land animals, the sauropod dinosaurs, did have more cartilage in their skeletons than any adult mammal has. All their bones ossified, but the ends of their limb-bones retained thick cartilage caps -- maybe as much as 10-15 cm thick in the cases of large animals. Why was this? Cartilage is more resilient and flexible than bone, so would have provided a cushion for the sauropods' great weight. The thing about cartilage caps in long bones is that they are subject only to relative small and simple compressive forces, whereas the bones themselves have to withstand bigger and more complex bending and twisting forces. So this is a pretty good engineering solution.