synapsid

(adjective)

animals that have one opening low in the skull roof behind each eye; includes all living and extinct mammals and therapsids

Related Terms

Examples of synapsid in the following topics:

  • Evolution of Amniotes

    • The initial split was into synapsids and sauropsids.
    • Synapsids include all mammals, including extinct mammalian species.
    • Synapsids also include therapsids, which were mammal-like reptiles from which mammals evolved.
    • Anapsids have no temporal fenestrae, synapsids have one, and diapsids have two.
    • Anapsids have no openings, synapsids have one opening, and diapsids have two openings.

  • Evolution of Mammals

    • Mammals are synapsids: they have a single opening in the skull.
    • They are the only living synapsids as earlier forms became extinct by the Jurassic period.
    • The early, non-mammalian synapsids can be divided into two groups: the pelycosaurs and the therapsids.
    • By the mid-Triassic, there were many synapsid species that looked like mammals.
    • The jawbone also shows changes from early synapsids to later ones.

  • Evolution of Reptiles

    • Soon after the first amniotes appeared, they diverged into three groups (synapsids, anapsids, and diapsids) during the Permian period.
    • These groups remained inconspicuous until the Triassic period when the archosaurs became the dominant terrestrial group due to the extinction of large-bodied anapsids and synapsids during the Permian-Triassic extinction.

  • Characteristics of Mammals

    • This arrangement of jaw and ear bones aids in distinguishing fossil mammals from fossils of other synapsids.