The first groups of reptile-like animals evolved about 320 million years ago. About 40 million years later, (very quickly by geologic standards), a group called therapsids branched off, which eventually became modern mammals. Other groups of reptiles split off over the next 120 million years, and one branch called the archosaurs were very successful.
Archosaurs were the ancestors of dinosaurs and crocodiles, but they were only distantly related to modern snakes, lizards, and turtles, groups that had split off at different times. Then, 65 million years ago there was a massive extinction event, and all dinosaurs were killed except for a single group of feathered dinosaurs. These evolved over the next 65 million years into modern birds.
Although technically, according to the phylogenetic system, birds, reptiles, and mammals all share a reptile-like ancestor.
So, the correct option is 'Birds and mammals'.