Therapsida

Therapsida is a clade of synapsids that includes mammals and their extinct relatives. Its members show a broad evolutionary trend toward mammal-like skulls, teeth, and limbs.

Synapsida: Synapsida is the amniote clade that includes mammals and their extinct relatives, distinguished ancestrally by a single temporal opening in the skull. Therapsids are nested within this broader lineage.
Temporal fenestrae in synapsids: Temporal fenestrae in synapsids are openings behind the eye sockets that provide space for jaw muscles. Their expansion and surrounding bone changes shaped therapsid skulls and jaw function.
Biarmosuchia: Biarmosuchia is an early-diverging group of therapsids, generally known from Permian fossils. Its members retain relatively primitive features near the base of therapsid diversity.
Pelycosaur: Pelycosaur is an informal name for early synapsids that lived mainly during the Carboniferous and Permian periods. These earlier synapsids provide context for the emergence of therapsids.
Mammalia: Mammalia is the clade of vertebrates whose living members include monotremes, marsupials, and placentals. Mammals are living descendants within the therapsid lineage.
Amniote: An amniote is a vertebrate whose embryo develops within an amnion or equivalent membranes. Therapsida belongs to the amniote branch of vertebrate evolution.
Heterodont dentition: Heterodont dentition is a tooth arrangement with distinct types specialized for different functions. Many therapsids developed differentiated teeth for cutting, piercing, or crushing food.
Dinocephalia: Dinocephalia is a group of large-bodied Permian therapsids that includes herbivores and predators. Their varied skulls show the ecological range among early therapsids.
Permian: The Permian is the geologic period from about 299 to 252 million years ago, preceding the Triassic. Therapsids diversified extensively during this period.
Mammalian evolution: Mammalian evolution is the history of changes leading from early synapsids to modern mammals. Therapsid transformations form a central sequence in this evolutionary history.

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