Describe the features of therapsids that suggest this group was transitional to reptiles and mammals.

Although Archaeopteryx is by far the best-known of the transitional fossils, it is not the only one, or even the best. The fossil transition from reptile to mammal is one of the most extensive and well-studied of all the transitions, and detailed series of fossils demonstrate how this transition was accomplished. It is not, therefore, surprising that the creationists do not talk much about the reptile-mammal series, and when they do, most of what they say is demonstrably untrue.