Definition of dimetrodon
: an extinct, North American, primitive synapsid (genus Dimetrodon) of the early Permian comprising terrestrial carnivores of moderate size having both canine and shearing teeth and distinguished by a large dorsal crest resembling a sail supported by greatly elongated bony processes of the spinal column
Note: Dimetrodons are often mistaken for dinosaurs but were extinct more than 35 million years before dinosaurs appeared on earth.
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