Stuart S. Sumida
Biology 342
(Simplified)Phylogeny of Archosauria
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.
ARCHOSAURIA
ARCHOSAURS ARE DIAPSID
REPTILES
ARCHOSAURIA INCLUDES:
•Crocodylomorpha
•Pterosauria
•Dinosasuria
•Aves (Birds)
Crocodylomorpha Pterosauria Eoraptor Herrerasauridae Saurischia Ornithischia
Archosauria
Alligator mississippiensis
Note presence of bony “scutes” or osteoderms in skin.
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.
Reconstruction of the pterosaur
Eudimorphodon in pronograde,
bipedal walking.
TERMS FOR POSTURE
Pronograde: backbone parallel to ground
Orthograde: backbone perpendicular to
ground
BIPEDAL and QUADRUPEDAL are not
postural terms.
Pterydactylus
Reconstruction of
Pteranodon
THE MOST PRIMITIVE DINOSAURS
Crocodylomorpha Pterosauria
Herrerasauridae? Saurischia Ornithischia
Dinosauria
Archosauria
THE MOST PRIMITIVE DINOSAURS
Crocodylomorpha Pterosauria
Herrerasauridae Saurischia Ornithischia
A perforate acetabulum
Crocodylomorpha Pterosauria
Herrerasauridae? Saurischia Ornithischia
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
Skull reconstruction
Herrerasaurus ischigualastensis
Reconstruction
24 presacral vertebrae; and the vertebrae are relatively shorter than more primitive forms.
Herrerasaurus ischigualastensis
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
Cerapoda
Thyreophora
Most ornithischians
are herbivores.
SAURISCHIA
Prosauropoda
Sauropoda
Theropoda
Eoraptor
Sauropodomorpha
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.
SAUROPODOMORPHA
Upper 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
BIPEDAL, Extremely
large thumb with
enlarged claw.
Seismosaurus, a
more derived
sauropod.
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.
Theropod Feet: Note missing V.
I
IV
II
III
Coelophysis, skull
Coelophysis: reconstructed in northern New Mexico
Sauropodomorpha
THEROPODA
Coelophysoidea
Saurischia
*
Theropoda
Abelisauridae
Spinosauroidea
Allosauroidea
Tetanurae
Compsognathidae
Tyrannosauroidea
Coelurosauria
Ornithomimosauria
Oviraptorisauria
Maniraptora
*Ceratosauria
Dromaeosauridae
Troodontidae
Avialae
Daspletosaurus
T. rex – Predator or scavenger?
Probably both…
How fast could T.
rex really run?
Could it run 25
miles per hour?
40?
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.
Sauropodomorpha
THEROPODA
(?)Eoraptor
(?)Herresauridae
Coelophysoidea
Saurischia
Abelisauridae
Theropoda
Spinosauroidea(?)
Allosauroidea
Tetanurae
Compsognathidae
Tyrannosauroidea
Coelurosauria
Ornithomimosauria
Oviraptorisauria
Maniraptora
Dromaeosauridae
Troodontidae
Avialae
AVIALAE: TRUE BIRDS
Archaeopteryx lithographica