EVERYDAY SCIENCE

Detailed explanation-1: -1) Synapsid-Skull possessing a lower temporal fenestra only. Amniotes with this skull condition form the monophyletic clade Synapsida, which includes the mammals and their extinct ancestors, the mammal-like reptiles. Note that in the Mammalia, the lower temporal fenestra has merged with the orbit.

Detailed explanation-2: -Unlike other amniotes, synapsids have a single temporal fenestra, an opening low in the skull roof behind each eye orbit, leaving a bony arch beneath each; this accounts for their name.

Detailed explanation-3: -They include mammals and mammal-like animals with one skull hole on each side. Their temporal fenestrae are fused. Synapsids were the largest vertebrates during the Permian period.

Detailed explanation-4: -syn·ap·sid sə-ˈnap-səd. : any of a subclass (Synapsida) of terrestrial vertebrates (such as the pelycosaurs and therapsids) having a single pair of lateral temporal skull openings. Note: Traditional classifications typically consider synapsids to be mammal-like, extinct reptiles ancestral to mammals.