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Humans are synapsids, as well. Most mammals are viviparous and give birth to live young rather than laying eggs with the exception being the monotremes. Triassic and Jurassic ancestors of living mammals, along with their close relatives, had high metabolic rates. This meant consuming food (generally thought to be insects) in much greater quantity.
The combination of small eggs and the absence of a larval stage, where posthatching growth occurs in anamniotic tetrapods before turning into juveniles, would limit the size of the adults. This is supported by the fact that extant squamate species that lay eggs less than 1 cm in diameter have adults whose snout-vent length is less than 10 cm.
The first fully terrestrial vertebrates were reptilian amniotes — their eggs had internal membranes that allowed the developing embryo to breathe but kept water in. This allowed amniotes to lay eggs on dry land, while amphibians generally need to lay their eggs in water (a few amphibians, such as the common Suriname toad, have evolved other ways of getting around this limitation).
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 ...
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.
Dimetrodon (/ d aɪ ˈ m iː t r ə ˌ d ɒ n / ⓘ [1] or / d aɪ ˈ m ɛ t r ə ˌ d ɒ n /; [2] lit. ' two measures of teeth ') is an extinct genus of non-mammalian synapsid belonging to the family Sphenacodontidae that lived during the Cisuralian age of the Early Permian period, around 295–272 million years ago.
Subclass Synapsida – synapsids, including mammal-like reptiles-now a separate group (often thought to be the ancestors of mammals) Subclass Anapsida – anapsids; Class Mammalia – mammals Subclass Prototheria – egg-laying mammals, including monotremes; Subclass Allotheria – multituberculates
Edaphosaurus (/ ˌ ɛ d ə f oʊ ˈ s ɔːr ə s /, meaning "pavement lizard" for dense clusters of teeth) is a genus of extinct edaphosaurid synapsids that lived in what is now North America and Europe around 303.4 to 272.5 million years ago, [1] during the Late Carboniferous to Early Permian.