Plains are the typical landform throughout, although portions of the ecoregion, for example the Sandstone Hills and Arbuckle Upland, have more variable relief .
(Plains; are; the typical landform throughout) (the Sandstone Hills and Arbuckle Upland; have; more variable relief)
Plains the Sandstone Hills and Arbuckle Upland
are have
the typical landform throughout
more variable relief