Pelycosaurs and Therapsids were

Options

A. Sauropsids
B. Synapsids
C. Sphenopsids
D. Dinosaurs

Answer

### Step-by-Step Solution:

1. **Identify the Groups**: Pelycosaurs and Therapsids are both groups of extinct animals.

2. **Classification**: Both of these groups fall under the category of synapsids. Synapsids are a clade of animals that are more closely related to mammals than to reptiles.

3. **Characteristics of Synapsids**: Synapsids are characterized by having a single temporal fenestra (an opening in the skull behind the eye), which differentiates them from diapsids (like reptiles) that have two.

4. **Evolutionary Significance**: Pelycosaurs are considered to be some of the earliest synapsids, often resembling reptiles but exhibiting some mammalian traits. Therapsids, on the other hand, are more advanced synapsids that show even more mammalian characteristics and are considered to be the ancestors of modern mammals.

5. **Historical Context**: Both groups thrived during the Permian period, which lasted from about 299 million years ago to 251 million years ago. They were among the largest vertebrates of their time.

6. **Conclusion**: Therefore, Pelycosaurs and Therapsids can be classified as synapsids, which are a group of animals that are closely related to mammals.

### Final Answer:
Pelycosaurs and Therapsids were synapsids, a group of animals closely related to mammals.

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