Evolution of Archosaurs

or “ruling reptiles”

Theropod Dinosaurs

Coelurosaur theropods

Deinonychus

Tyrannosaurus

Carnosaur theropods

Trends in the evolution of birds

• Enlargement of eyes and brain

• Increased metabolic rate

• Loss of teeth

• Lengthened of forelimb as wing

• Keeled breastbone for flight muscles – carinate sternum

• Pennaceous feathers for flight

• Loss of digits, claws, and fusion of bones in wing – carpometacarpus

• Loss of digits and fusion of bones in foot – tarsometatarsus

• Loss and fusion of bones in tail – pygostyle

• Reversal and spreading of pubic bones – large eggs, respiration?

Scipionyx

Preserved viscera

Sinosauropteryx

Cretaceous

Downy feathers

Sinornithosaurus – Cretaceous China

Downy head feathers

wing feathers

Caudipteryx

Cretaceous

China

Caudipteryx reconstruction

Jehelornis

Cretaceous China

Jehelornis

Cretaceous China

tail plume

Protoarchaeopteryx

reconstruction

Rahonavis

Cretaceous

Madagascar

Rahonavis

Cretaceous

Madagascar

Bird or Dromaeosaur?

Deinonychus

Microraptor - four-winged dromaeosaur

Cretaceous

Microraptor - Cretaceous

leg feathers

Archaeopteryx

Jurassic

Archaeopteryx reconstruction

Iberomesornis

Enantiornithes

Early Cretaceous

Spain

tail

Pygostyle - fused caudal vertebrae

Bohaiornis

Enantiornithes

Cretaceous

China

Thin section through bone

resting lines

Confuciusornis

Early Cretaceous

China

toothless beak

fused pygostyle

powered flight

Confuciusornis

Early Cretaceous

China claws on wing

Neornithes - modern birds

Anneavis

Cenozoic Early Eocene fused carpometacarpus

fused tarsometatarsus

fused carpometacarpus

fused tarsometatarsus

fused pygostyle

carinate sternum