cotylosaur definition by American Heritage Dictionary
The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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.
Origin: Greek kotulē, hollow object, socket + Greek sauros, lizard.
cotylosaur - Science Definition
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.