140-170 million years old

TRAIT \ TYPE	REPTILE	ARCHAEOPTERYX	BIRD
Feathers	no	yes	yes
Hind limb claws adapted for perching i.e., opposable hallux	no	yes	yes
Furcula from fused clavicle	some theropods have unfused clavicles	yes	yes
Pubis elongate and directed backward	some theropods	yes	yes
beak	no	no	yes
Vertebra in trunk region fused	no	no	yes
Hollow (pneumatic) bones	some	yes	yes
Elongate cerebral hemispheres Cerebellum behind mid-brain	yes	yes	no
Concave articular facets on cervical vertebrae	yes	yes	no
tail composed of free vertebrae	yes	yes (with feathers)	no, short and fused to form pygostyle
teeth	yes	yes	no
Ribs with uncinate processes articulated with sternum	no	no	yes
keel sternum	no	no	yes
Sacrum occupies 6 vetebra	yes	yes	no, 11-23 vertebra
Archosaurian pelvic femur joint	yes	yes	no
Free metacarpals	yes	yes	no
Free metatarsals	yes	yes	no
Nasal opening forward (preorbital fenestra)	yes	yes	no
Deltiod ridge of humerus and radial and ulnar condyles face forward	yes	yes	no
Claws on unfused digits of forelimbs	yes	yes	some embryonic, 3 as juvenile
Developed fibula	yes	yes	no, greately reduced
Gastralia (dermal bone in wall of abdomen)	yes	yes	no

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