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Bird to Dinosaur Transition (Skeleton Similarities Birds vs Theropods…
Bird to Dinosaur Transition
Origin of Birds from Dinosaurs
Theropod lineage of dinosaurs
changed body to move into air
Fossil preservation such that = best transition to observe
Gradual evolution
in one dinosaur lineage
Bird body plan evolved over ~100 Myr
of theropod evolution
Flying birds diversified explosively
once established
Theropods
Very diverse = Mostly carnivorous dinosaurs, some herbivores
Birds evolved from theropods - lineage of smaller theropods
e.g. Velociraptor, T-rex
Skeleton Similarities Birds vs Theropods
Long, S-shaped curved neck
Wishbones
- collar bones fused up
Arms fold against body
requires special wrist bone
Pelvis curves backward
(retroverted)
Hinge-like ankle joint
Shared unique characters linking theropods & birds
e.g. Velociraptor
Bird-like Dinosaur Features found
Hollow bones
suggests soft tissue anatomy
Huge brains
suggesting keen sense
Pneumatic openings
sinuses throughout skull
in bones for air sacs
CAT scan space in skull -
3D model how cavities filled (brain/ear/sinuses)
V Efficient Lungs
take in oxygen when breathing in & out
inhale air into lunge when exhaling
air stored in air sacs attached to lung
marks where air sacs found in bodies
Parents
brooding eggs
Fast Theropod Growth Rates
Growth rings in dinosaur bones (one per year)
e.g. Tyrannosaurs
Didn't exceed 30 years
Grew rapidly, died young
First 10 years - slow growth (childhood)
10-20 years - Exponential growth
(2kg/day)
Birds grow even more rapidly
Suggests dinosaurs
= warm-blooded like birds
Feathers
Dinosaur fossils with feathers
Atleast 20 species with feathers (1000s skeletons)
Mostly meat-eaters, some plant-eating
Chinese 'Feathered Dinosaurs'
Lived around dense forests near volcano
Ashfall buried them suddenly (pyroclastic flow)
No chance to decay