Sidor, Christian Department of Biology, University of Washington, Seattle, Washington.
Last reviewed:August 2019
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A paraphyletic grade of fossil (extinct) synapsids that is ancestral to later forms, such as the therapsids and mammals. (Paraphyletic means not containing all of the descendants of the most recent common ancestor.) Modern taxonomic practice does not formally recognize ancestral groups—hence the use of pelycosaur-grade synapsid or Permo-Carboniferous synapsid for this assemblage.
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