For example, instead of having a row of teeth that were all the same size and shape, therapsids had teeth with different shapes for different functions.
These changes indicate that therapsids had a more versatile range of motion than other land vertebrates, which made them able to move faster and more energetically.
These animals had the active, energetic lifestyle of other therapsids, but their small size meant they required less energy—which is important when you're trying to survive a mass extinction.
Later carnivorous therapsids could even chew their prey rather than ripping off chunks of meat and swallowing them whole, like what reptiles and birds still do today.