Dunkeleosteous 9 meters long major predator a note on

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Unformatted text preview: were large! Dunkeleosteous: 9 meters long, major predator A note on the evolution of bone •! Regarding the positions of vertebrae and bone on the vertebrate cladogram, organisms can have vertebrae made out of cartilage. This is what occurs in lampreys. They are not vertebrae in the sense of the human skeleton, but they are bits of cartilage that sit above the notochord as neural arches or spines. Lampreys do not have bone. •! Professor Wainwright says: Cartilage is not necessarily an ontogenetic or evolutionary precursor of bone. It's a versatile, high performance skeletal material in its own right. Of course there are many adult cartilaginous structures, but also, lots of bones do not develop by replacing cartilage (all dermal bones for example). A number of non-vertebrate metazoans have cartilage and no bone (molluscs are a good example). •! Professor Wainwright also says that bone first occurred in the dermal skull of ostracoderms, a paraphyletic group, but even there it was not in the vertebrae (these were cartilaginous)....
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This document was uploaded on 04/13/2013.

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