Synapsids get their name from the pattern of openings, or windows, on the sides of the skull bone, with
one main opening in each upper side. Synapsids appeared about 300 million years ago and during the
Permian Period they were the main large land animals, with both plant- and meat-eaters. They faded as
the dinosaurs came to domination in the. Triassic, but some of their kind gave rise to the first mammals.