While the cenozoic is often incorrectly referred to as the "age of mammals", in what time period were synapsids the dominant terrestrial vertebrates?
a. permian
b. triassic
c. jurassic
d. cretacous
e. devonian

The correct answer is A. Permian.

Explanation

The synapsids were terrestrial vertebrate mammals or animals related to them rather than to reptiles or birds that lived during the Permian (a period that began about 299 million years ago and ended about 251 million years ago) and were the dominant terrestrial vertebrates during it. These animals survived until the Triassic; however, due to the Permian-Triassic extinction, they were not the predominant vertebrate as in the previous period. Later, during the Cretatic and Jurassic periods, their development was minimal and did not have great importance as reptiles were dominant in this period. So, the correct answer is A. Permian.