Context: Therapsids descended from pelycosaurs in the Middle Permian, about 265 million years ago, and became the dominant land vertebrates. They differ from basal eupelycosaurs in several features of the skull and jaws, including: larger temporal fenestrae and incisors which are equal in size. The therapsid lineage leading to mammals went through a series of stages, beginning with animals that were very like their pelycosaur ancestors and ending with probainognathian cynodonts, some of which could easily be mistaken for mammals. Those stages were characterized by:

Question: From which dinosaur group did Therapsids descend from?
Answer: pelycosaurs

Question: Around what time did Therapsids become the dominant land animal?
Answer: 265 million years ago

Question: At which group did Therapsids end with?
Answer: probainognathian cynodonts

Question: When did basal eupelycosaurs descend from pelycosaurs?
Answer: Unanswerable

Question: What did the therapsid lineage do in the Middle Permian, 265 million years ago?
Answer: Unanswerable

Question: How do Probainognathian cynodonts differ from the therapsid lineage?
Answer: Unanswerable

Question: What are some characteristics that show how mammals differ from pelycosaurs?
Answer: Unanswerable

Question: What animal was at the end stage of the Middle Permian?
Answer: Unanswerable