Phylum Chordata - Chordates Internal skeleton with muscle ...

Class Aves - BirdsMost successful of all terrestrial vertebratesgreat diversity, 8800 speciesKey Characteristics of BirdsProduce amniotic eggs - like reptilesHave keratin scales on feet and legs - like reptilesLack teeth - developmental mutants have reptile-like teethHave very small tail - unlike reptilesFeathersModified reptilian scalesProvide lift for flight and insulateDevelop from folliclesHas shaft, with barbs, withbarbules, with interlocking hooksFlexible, light-weight, and strongCan be replaced, like scalesFlight skeletonBird bones are thin, hollow,and light-weightMany have internal struts tostrengthen the bone withlittle added weightMany bones are fused toeach other - reducesnumberHave fused collarbones(wishbone) for recoil ofwings during flightHave keeled breastbone - forattachment of flightmuscles