synapsid

Synapsida is often a misspelling of synapsid.

Synapsida has no English definition.

As an adjective synapsid is

pertaining to the class Synapsida, of animals which have an opening low in the skull roof behind each eye, leaving a bony arch beneath each.

As a noun synapsid is

any animal (including all mammals) of the class Synapsida.

As nouns the difference between synapsid and cynodont

is that synapsid is any animal (including all mammals) of the class synapsida while cynodont is (zoology) any of several small carnivorous synapsids in the clade , ancestral to mammals and extinct close relatives.

As an adjective synapsid

is pertaining to the class synapsida, of animals which have an opening low in the skull roof behind each eye, leaving a bony arch beneath each.