Phylum Chordata - Chordates Internal skeleton with muscle ...

Dry skin with scales or armor reduces water lossScales develop as surface cells fill with protein keratinKeratin is also used for mammal hair and bird feathersThoracic breathing - increase volume of air inspiredExpand and contract rib cage to suck air in and force it outCapacity limited only by volume of lungsImproved leg design -legs placed moreventrally under trunkallows better support ofthe body and greatermobilityallows larger body sizeReptile Evolution - Reptiles were the dominant land animals for250 myFour major lineages evolved in series: Pelycosaurs, Therapsids,Thecodonts, DinosaursPelycosaurs - improved predatorssynapsid skull with temporal openings allowedbetter muscle attachment and more powerful biteDominant terrestrial vertebratesfor 50 million yearsReplaced by Therapsids