Defining Birds

Question 1

Q: What are some definitions of “birds”?

Answer 1

A:

Descendants of Archaeopteryx.
Problem: Some studies place Archaeopteryx closer to dromaeosaurs than to modern birds.
Feathered dinosaurs.
Problem: Includes dinosaurs like tyrannosaurs, which challenges traditional bird definitions.
Flying dinosaurs.
Problem: Difficult to distinguish flying from gliding species.
Crown group dinosaurs.
Definition: The last common ancestor of all living birds and its descendants.

Question 2

Q: What clade do paleontologists often use to define flying dinosaurs, including Archaeopteryx?

Answer 2

A: Avialae.