"From 230 to 570 million years ago" . . . . . "Late Ordovician through Early Devonian annotated correlation chart and Brachiopod range charts for the southern midcontent region, U.S.A., with a discussion of Silurian and Devonian conodont faunas"@en . . . . . . . "Late Ordovician through early Devonian annotated correlation chart and Brachiopod range charts for the Southern Midcontinent region, U.S.A., with a discussion of Silurian and Devonian conodont faunas"@en . . . . . . . . . . . . . . . . "Southwestern states" . .