By what time had mouse-sized viviparous mammals evolved?
Corvidae arthropods birds backbones keratin Jurassic front paws Parakeets.
A B C D E F G H
By what time had mouse-sized viviparous mammals evolved? (A) Corvidae (B) arthropods (C) birds (D) backbones (E) keratin (F) Jurassic (G) front paws (H) Parakeets.