cotylosaur

cot·y·lo·saur  (ktl--sôr)

n.

Any of an extinct order (Cotylosauria) of massive primitive reptiles of the Carboniferous and Permian periods that included the ancestors of all of the reptiles. Also called root reptile, stem reptile.

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[Greek kotul, hollow object, socket + Greek sauros, lizard.]

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cotylosaur  (ktl--sôr)

Any of a number of extinct reptiles of the group Cotylosauria or Captorhinida of the Carboniferous and Permian Periods that include the ancestors of all terrestrial vertebrates except for amphibians. Cotylosaurs evolved from early amphibians, had four sprawling legs and a long tail, and a skull without temporal openings. Also called stem reptile.