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The apparent absence of these glands in non-mammaliaformes may suggest that fur did not originate until that point in synapsid evolution. [40] It is possible that fur and associated features of true warm-bloodedness did not appear until some synapsids became extremely small and nocturnal, necessitating a higher metabolism. [40]
Synapsids had one opening on each side, while diapsids (a branch of Sauropsida) had two. An early, inefficient version of diaphragm may have evolved in synapsids. The earliest synapsids, or "proto-mammals," are the pelycosaurs. The pelycosaurs were the first animals to have temporal fenestrae. Pelycosaurs were not therapsids but their ancestors.
Therapsida [a] is a clade comprising a major group of eupelycosaurian synapsids that includes mammals and their ancestors and close relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more underneath the body, resulting in a more "standing" quadrupedal posture, as opposed to the lower sprawling posture of ...
The synapsid lineage became distinct from the sauropsid lineage in the late Carboniferous period, between 320 and 315 million years ago. [2] The only living synapsids are mammals, [3] while the sauropsids gave rise to the dinosaurs, and today's reptiles and birds along with all the extinct amniotes more closely related to them than to mammals. [2]
Pelycosaur (/ ˈ p ɛ l ɪ k ə ˌ s ɔːr / PEL-ih-kə-sor) [1] is an older term for basal or primitive Late Paleozoic synapsids, excluding the therapsids and their descendants. Previously, the term mammal-like reptile had been used, [2] and pelycosaur was considered an order, but this is now thought to be incorrect and outdated.
The evolution of a secondary palate, and the separation of the mouth from the nasal cavity, may have increased ventilation efficiency associated with high levels of aerobic activity; gorgonopsians did not have a bony secondary palate, but possibly had one of soft tissue. Nonetheless, the secondary palate could have instead aided in eating large ...
Nonetheless, recent studies on Permian synapsid coprolites show that more basal therapsids may have had fur, [2] and at any rate fur was already present in Mammaliaformes such as Castorocauda and Megaconus. Skull of Morganucodon, a member of Mammaliaformes. Early cynodonts had numerous small foramina on their snout bones, similar to reptiles.
These lists of synapsids collectively include every genus that has ever been included in the clade Synapsida- the mammals and their evolutionary precursors. The lists includes accepted genera along with those now considered invalid, doubtful (nomina dubia), not formally published (nomina nuda), junior synonyms of more established names, as well as genera that are no longer considered synapsids.