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 4 th 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

Crocodylomorpha Pterosauria Herrerasauridae? Saurischia Ornithischia Archosauria Dinosauria THE MOST PRIMITIVE DINOSAURS

Crocodylomorpha Pterosauria Herrerasauridae Saurischia Ornithischia THE MOST PRIMITIVE DINOSAURS

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: SAURISCHIANORNITHISCHIAN (Note position of pubis.)

ORNITHISCHIA Stegosauria Ankylosauria Pachycephalosauria Ceratopsia Ornithopoda Thyreophora Cerapoda Most ornithischians are herbivores.

Prosauropoda Sauropoda Theropoda SAURISCHIA Sauropodomorpha Eoraptor

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 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.

I II III IV Theropod Feet: Note missing V.

Coelophysis, skull

Coelophysis: reconstructed in northern New Mexico

THEROPODA Sauropodomorpha Coelophysoidea Abelisauridae Spinosauroidea Allosauroidea Compsognathidae Tyrannosauroidea Ornithomimosauria Oviraptorisauria Dromaeosauridae Troodontidae Avialae Theropoda Saurischia Tetanurae Coelurosauria Maniraptora * * Ceratosauria

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.

THEROPODA Sauropodomorpha (?)Eoraptor (?)Herresauridae Coelophysoidea Abelisauridae Spinosauroidea(?) Allosauroidea Compsognathidae Tyrannosauroidea Ornithomimosauria Oviraptorisauria Dromaeosauridae Troodontidae Avialae Theropoda Saurischia Tetanurae Coelurosauria Maniraptora

AVIALAE: TRUE BIRDS

Archaeopteryx lithographica