Evolving the Musculoskeletal System

Bolder-dash, please do not reply to this message in this thread. Please take these issues to your New name for evolution, "The Bacteria Diet" thread. --AdminAs Meldinoor pointed out, we can't be certain of the exact route the evolution of the skeleton took. What we can do, though, is to look at fossils, and at still existing animals with primitive skeletons, to work out which bits probably came first.The oldest skeletons were cartilage, which was only (partially) replaced by bone later. Looking at the near relatives of the vetebrates, we find the lancelets. These little creatures don't have any skeleton, nor do they have a proper brain, a heart, or any paired fins. They do, however, have little bits of cartilage. These aren't randomly strewn around the body, they're in places like the tail, where stiffness helps them get the propulsion they need to burrow into the sand, and supporting the gill arches.The big step to the development of a skeleton came with the evolution of a skull. We can be confident the skull came first, as there are living and fossil animals, like hagfish, which have skulls but no other skeleton. The advantage of a skull is, I hope, obvious. It protects the newly evolved brain from damage. Sexual selection is unlikely to have played much of a role in any of this - the skeleton just had clear survival advantages.Edited by Admin, : Add moderation comment.

I think you go a bit confused here - fossil coelacanths range in size from tiny to massive. Modern coelacanths have a total length of between about 4' and 6'. Coelacanthus, the type genus, were no longer than 3'. Polyosteorhynchus doesn't seem to have gotten any bigger than 7" or so, while giant Cretaceous coelacanths like Megalocoelacanthus have been discovered with lengths up to 11'.Clearly though, coelacanths haven't remained the same as time has gone by.