Synapsids

Definition

Synapsids are a group of amniotes that includes mammals and their extinct relatives. They are characterized by a single temporal fenestra, an opening in the skull behind each eye.

5 Must Know Facts For Your Next Test

1. Synapsids include both modern mammals and their extinct relatives, such as pelycosaurs and therapsids.
2. The single temporal fenestra is a key feature that distinguishes synapsids from other amniotes like diapsids.
3. Synapsids first appeared in the late Carboniferous period, around 320 million years ago.
4. Therapsids, a subgroup of synapsids, are considered ancestors to modern mammals and show early signs of mammalian characteristics.
5. The evolutionary transition from synapsid reptiles to true mammals involved significant changes in jaw structure, ear bones, and limb posture.

Review Questions

Related terms

Amniotes: Vertebrates that have an egg equipped with an amnion, allowing them to lay eggs on land or retain them within the mother.

Diapsids:

A group of amniotes that possess two temporal fenestrae in their skulls, including reptiles like lizards, snakes, and birds.

Therapsids: A subgroup of synapsids that includes ancestors to mammals and shows some early mammalian features.