"Pélycosauriens." . . "From 230 to 280 million years ago" . . "Paléontologie Permien." . . . . . . "The history of the Pelycosauria : with a description of the genus Dimetrodon, Cope"@en . . . . . . . . . . . . . "The History of the Pelycosauria, with a description of the genus Dimetrodon, Cope" . . . "The history of the Pelycosauria with a description of the genus Dimetron, Cope"@en . . "The history of the Pelycosauria with a description of the genus Dimetron, Cope" . . . . .