vertebrates; birds Flashcards
birds evolved from
small, predatory dinos
evolution of birds
- transition from fuzz to flight feathers
- loss of teeth
- loss of tail
- fusion and modification of skeletal elements
intermediates between dinos and birds
- archaeopteryx: ancestral reptilian traits, derived bird-like traits, flight feathers
- aurornis: clawed digits on forelimb, sharp teeth, dino fuzz, unable to fly
- anchiornis:
most basal bird
aurornis
feathers likely appeared in
compsognathids
which dino-bird intermediate had feathers of modern birds
archaeopteryx
describe changes in digits
- therapods had forelimbs with small 4 and 5 digits, digit 3 longest
- ceolophysoids, digit 5 lost, digit 2 and 3 equal
- in allosaurids, digit 4 lost, and 2 because longer than 3
summary
- 5 lost first, 2 grew to be equal to longest 3
- 4 lost, 2 become longer than 3
- so in living birds they have 1, 2, 3 and 2 is longest
other evolvements of birds
- reducted, loss and fusion of skeletal elements
- reduction in body size
- outer cortex of bones thinner but more sense
- bones hollow or have trabeculae
bird sternum evolution
became larger and evolved a central keel to anchor the flight muscles
bird evolution forelimbs
became longer than hindlimbs as main form of locomotion switched from running to flying
bird evolution teeth
lost
flightless birds
LOST the ability to fly secondarlily
success of birds because
- endothermic
- flight
beak
keratinized structure derived from skin
grows continuously
uropgyial gland
- dorsal surface of tail
- 2 lobes that open to single papilla
- lipoid secretion; waterproof and moisturize feathers
- preen to distribute
