/theuh rap"sid/, n.
1. any of various groups of mammallike reptiles of the extinct order Therapsida, inhabiting all continents from mid-Permian to late Triassic times, some of which were probably warm-blooded and directly ancestral to mammals.
2. of or pertaining to the Therapsida.
[ < NL Therapsida (1905), equiv. to Gk ther- (s. of thér wild beast) + apsid- (s. of apsís arch, vault, referring to the temporal arch of the skull) + NL -a neut. pl. ending (see -A1)]

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▪ fossil reptile order
      any member of a major order (Therapsida) of reptiles of Permian and Triassic time (from 299 million to 200 million years ago). Therapsids were the stock that gave rise to mammals. As early as the preceding Carboniferous Period (from 359 million to 299 million years ago), there appeared a distinct evolutionary line, beginning with the archaic mammal ancestors, order Pelycosauria, and leading toward mammals. From one pelycosaur family sprang the therapsids. Therapsids include mammals and other cynodonts; they form a subgroup of the Synopsida, one of the major branches of amniotes. Therapsids first appear in the Permian Period, during which they flourished and evolved into a number of mammal forms.

      Primitive therapsids are present as fossils in certain Middle Permian deposits; later forms are known from every continent except Australia but are commonest in the Late Permian and Early Triassic of South Africa. The limbs and limb girdles were modified for four-footed locomotion. The skull, as in mammals, had a single opening in the temporal region, bounded below by a bony arch. In most species the teeth were differentiated into mammal-like nipping incisors, large stabbing canines, and a series of grinding cheek teeth. The lower jaw, however, was reptilian in structure, being composed of seven bones instead of one as in mammals, and had a different, primitive articulation with the skull. In advanced forms, as in mammals, there was a bony palate in the roof of the mouth.

      A notable therapsid side branch was that of the herbivorous dicynodonts (two-tuskers), in which upper canines were retained but the other teeth were replaced by a horny bill. Among carnivorous therapsids, gorgonopsians and therocephalians were characteristic of the Permian, and cynodonts and bauriamorphs were advanced Triassic representatives. A few therapsids were still present in the Late Triassic and even into the Jurassic, but most had by then become extinct or had evolved into primitive mammals.

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Universalium. 2010.

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Look at other dictionaries:

  • therapsid — noun Etymology: New Latin Therapsida, from ther mammal (from Greek thēr wild animal) + apsid , apsis arch, vault more at fierce, apsis Date: 1912 any of an order (Therapsida) of Permian and Triassic syrapsid reptiles considered ancestors of the… …   New Collegiate Dictionary

  • therapsid — noun Any extinct reptile, of the order Therapsida; thought to be direct ancestors of the mammals …   Wiktionary

  • therapsid — [θɛ rapsɪd] noun Palaeontology a fossil reptile of a large group including the cynodonts, related to the ancestors of mammals. Origin early 20th cent.: from mod. L. Therapsida (name of an order), from Gk thēr beast + hapsis, hapsid arch… …   English new terms dictionary

  • therapsid — the·rap·sid …   English syllables

  • therapsid — the•rap•sid [[t]θəˈræp sɪd[/t]] n. pal any of various mammallike reptiles of the extinct order Therapsida, inhabiting all continents from mid Permian to late Triassic times • Etymology: < NL Therapsida (1905) = Gk thēr , s. of thḗr wild beast… …   From formal English to slang

  • therapsid — noun probably warm blooded; considered direct ancestor of mammals • Syn: ↑protomammal • Hypernyms: ↑synapsid, ↑synapsid reptile • Hyponyms: ↑Chronoperates paradoxus, ↑cynodont, ↑ …   Useful english dictionary

  • Tapinocephalia — ? † Тапиноцефалы Moschops capensis Научная классификация Царство: Животные Тип: Хордовые …   Википедия

  • Brithopus — This article is about the mammal like reptile species. For the diverse group of prehistoric reptiles, see Dinosaur. For the 1960 science fiction film, see Dinosaurus!. Brithopus Scientific classification …   Wikipedia

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  • Synapsid — Synapsids Temporal range: Late Mississippian Early Cretaceous, 320–100 Ma …   Wikipedia

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