Origin of Birds Flashcards
What was the intermediate form between dinosaurs and birds?
Archaeopteryx lithographica
When did Archaeopteryx live?
Jurassic period
Which group of diapsids survived the Permian extinction and ultimately diversified into the the dinosaurs?
Archosaurs. They also had other changes in bony elements along with the two temporal openings of the diapsids
Which groups are the only surviving members of the Archosaur lineage?
Birds and crocodiles
What two groups were dinosaurs classified into?
Saurischian and ornithischian
What was the defining characteristics of the saurischian dinosaurs?
The pubis bone was facing towards the head
What were the two main groups of saurischian dinosaurs?
Sauropods and theropods
What was the defining characteristic of the ornithischian dinosaurs?
The pubis bone was facing towards the tail
Are birds the descendants of the saurischian or the ornithischian dinosaurs?
The saurischian dinosaurs, from the theropod
What characters did Archaeopteryx share with modern birds?
- No teeth
- Expanded braincase from bone fusion
- 3 digits of forelimb fused and reduced
- Pelvic bones and several vertebrae fused
- Fewer caudal vertebrae
- Sternum enlarged and keeled
- Horizontal processes that strengthen the rib cage
