Dinosaur expert: Some paleontologists have claimed that birds are descendants of a group of dinosaurs called dromeosaurs. ████ ██████ ██ ███ ██████ ███████ █████ █████████ ████ ███████████ ████ ███████████████ ████ ███████ ██ █████ ████ ██ ████ ██████████ ███ █████ ██ █ █████ ████ ██ █████ █████████ ███ ████████ ████ ███████ ████ ████ ████ ██████████ ████ ████ ████ ██ ████████ ██ █████ ███████ ████ ███ ██████ █████ ██████████ ████████ ████ ███ ████████████████ █████ ██ ██████
The author concludes that birds are not descendants of dinosaurs called dromeosaurs. Why? Because the earliest bird fossils that have been discovered date much further back in history than the oldest known dromeosaur fossils.
The author assumes that the fact the earlier bird fossils are older than the earlier dromeosaur fossils proves that birds originated before dromeosaurs did.
The author assumes that there do not exist undiscovered dromeosaur fossils that are older than the earliest bird fossils that have been discovered.
The expert's argument depends on ████████ █████ ███ ██ ███ ██████████
Having similar characteristics ██ ███ █ ████ ████ █████ ██ ███████ ███ ██████████████ ████████
Dromeosaurs and birds █████ ████ ██████ ██████████
Knowledge of dromeosaur ███████ ███ ███ ████████ ████ ███████ ██ █████████
Known fossils indicate ███ ████████ █████ ██ ██████ ██ █████ ███ ████████████
Dromeosaurs are dissimilar ██ █████ ██ ████ ███████████ █████