BIOL10005 Lecture Notes - Lecture 29: Thumb, Quadrate Bone, Platypus
15 Aug 2018
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* vertebrae (backbone) forms around notochord (it protects the notochord) * internal and elaborate skeleton (cartilage or bone) * defined head with braincase (skull), and sensory organs (to hear, smell, taste, see) * jaws derived from gill arches of chordates. * earliest jawed fishes late silurian (420 mya) The evolution of legs (and the move to land): * most bony fishes have fins made of long rays of bone (ray-finned fishes) * some fishes developed more substantial bones in the fins (more robust structure that was capable for support) (lobe-finned fishes) e. g. lungfish ( have both lungs. * about 350 mya some of those lobe-finned fishes, living in shallow lagoons, developed these bones to be able to (cid:858)walk(cid:859) (cid:894)paddle in shallow water(cid:895) * these early amphibians had both gills and lungs (c. f. lungfish) * the first tetrapods had unusual limbs (8 digits) whereas now digits are more or less 5 digits. * modern day reptiles inhabit all continents except antarctica.
