Why are certain dinosaurs thought to have been related to birds?

Answer 1

Tyrannosaurus belonged to the clade Coeluosauria. Coelurosauria includes birds, maniraptorans, and Tyrannosaurs. However, birds did not descend from Tyrannosaurus or any of its immediate relatives.

Answer 2

Many of the small carnivorous dinosaurs had remarkably birdlike anatomy and are now known to have had feathers. Some were likely capable of flight.

Answer 3

Birds appear to have evolved from a group of small, carnivorous dinosaurs. Evidence in recent years has shown that dinosaurs were more like birds than modern reptiles.