Editing Synapsida (section)

===Primitive and advanced synapsids===
The synapsids are traditionally divided for convenience, into [[therapsid]]s, an advanced group of synapsids and the branch within which mammals evolved, and stem mammals, (previously known as [[pelycosaur]]s), comprising the other six more primitive families of synapsids.<ref>[[Michael J. Benton|Benton, Michael J.]] (2005).'' [[Vertebrate Paleontology (Benton)|Vertebrate Paleontology]]'', 3rd ed. Oxford: [[Blackwell's|Blackwell Science Ltd]]. {{ISBN|0-632-05637-1}}. p. 120.</ref> Stem mammals were all rather lizard-like, with sprawling gait and possibly horny [[scute]]s, while therapsids tended to have a more erect pose and possibly hair, at least in some forms. In traditional taxonomy, the Synapsida encompasses two distinct [[evolutionary grade|grades]]: the low-slung stem mammals have given rise to the more erect therapsids, who in their turn have given rise to the mammals. In traditional vertebrate classification, the stem mammals and therapsids were both considered [[order (biology)|orders]] of the subclass Synapsida.<ref name=Romer/><ref name=Carroll397/>