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Remember, we’re studying AMNIOTES.
Defined by:
EMBRYOLOGICAL FEATURES: amnion, chorion, allantois, yolk sac.
ANATOMICAL FEATURES: lack of an intertemporal bone.
ALSO, FUNCTIONAL FEATURES: • Costal breathing (inhaling using movement of the ribs).• Active exhalation using movement of ribs to push air out.
ARCHOSAURS ARE DIAPSID REPTILES
ARCHOSAURIA INCLUDES:•Crocodylomorpha•Pterosauria•Dinosasuria•Aves (Birds)
Crocodilians are capable of a variety of types of locomotion: swimming; slow-sprawling walk; a moderate speed “high walk;” and even galloping in some young or smaller ones.
PTEROSAURIA:Flying Reptiles of the Mesozoic
They are the closest relatives of dinosaurs, but they are not actually dinosaurs.
They used elongate 4th finger to support a wing.
TERMS FOR POSTURE
Pronograde: backbone parallel to ground
Orthograde: backbone perpendicular to ground
BIPEDAL and QUADRUPEDAL are not postural terms.
Crocodylomorpha Pterosauria Herrerasauridae? Saurischia Ornithischia
Archosauria
Dinosauria
THE MOST PRIMITIVE DINOSAURS
Herrerasauridae:
Upper Triassic of Argentina
2 – 4.5 meters long.
Long, low skull that is as long as the femur.
24 presacral vertebrae; and the vertebrae are relatively shorter than more primitive forms.
Herrerasaurus ischigualastensis
Reconstruction
24 presacral vertebrae; and the vertebrae are relatively shorter than more primitive forms.
Dinosaurian groups more derived than Herrerasaurs may be divided into two groups based on hip construction:
SAURISCHIAN ORNITHISCHIAN
(Note position of pubis.)
ORNITHISCHIA
Stegosauria Ankylosauria Pachycephalosauria Ceratopsia Ornithopoda
Thyreophora
Cerapoda
Most ornithischians are herbivores.
Eoraptor lunensis (“Dawn Raptor”)•From the Upper Triassic of Argentina.
•Once thought to be amongst the most primitive of dinosaurs. Now considered to be a primitive Saurischian.
SAUROPODOMORPHAUpper Triassic through end of Cretaceous
Features that define Sauropodomorpha primarily associated with adaptations for herbivory, large size and, later, graviportal locomotion:• Relatively small head• At least ten vertebrae in very long neck.• Teeth coarsely serrated.• Enlarged sacrum• Extremely large thumb with enlarged claw.
More primitive Sauropods
Seismosaurus, a more derived sauropod.
BIPEDAL, Extremely large thumb with enlarged claw.
THEROPODA
•Pronograde bipeds.•Pneumatic (hollow) bones.•Enlarged hand.•Vestigial digits IV and V on hand.•Highly extendable digits I-III on hand.•Compact, elongate, narrow foot – usually missing digit V.
THEROPODASauropodomorpha
Coelophysoidea
Abelisauridae
Spinosauroidea
Allosauroidea
Compsognathidae
Tyrannosauroidea
Ornithomimosauria
Oviraptorisauria
Dromaeosauridae
Troodontidae
Avialae
Theropoda
Saurischia
Tetanurae
Coelurosauria
Maniraptora
*
*Ceratosauria
Taking animal mass and the strength of both bone and soft tissue into consideration, T. rex tissues and bones would shatter if moving much over ten miles an hour…
For T. rex to be able to travel at 20 m.p.h. the amount of leg muscle mass required to generate that much force would be about 95% to 110% its total body mass. Clearly impossible.
If legs are allowed to account for 40-50% of body mass (very generous), a conservative estimate for “cruising speed” is 11 miles per hour.
THEROPODASauropodomorpha
(?)Eoraptor
(?)Herresauridae
Coelophysoidea
Abelisauridae
Spinosauroidea(?)
Allosauroidea
Compsognathidae
Tyrannosauroidea
Ornithomimosauria
Oviraptorisauria
Dromaeosauridae
Troodontidae
Avialae
Theropoda
Saurischia
Tetanurae
Coelurosauria
Maniraptora