Fig. 6.

Carboniferous time scale with superimposed family tree of tetrapods, including recent data on occurrences and allowing for uncertainty in parts of the tree. Arrows at the top of lines indicate that groups persisted into the Permian. The Devonian tetrapod tree is based on the study by Callier et al. (47). The Carboniferous tetrapod tree (6, 7, 35) is shown with the node for the origin of the crown group on those phylogenies marked by A. Alternative phylogenies (11, 12) place the node for the origin of the crown group at B. All phylogenies imply an origin for the crown group no later than the early to mid-Viséan. Casineria is placed incertae sedis among the stem amniotes, and the Burnmouth foot is placed outside the tree. Whatcheeriids may extend into the Late Devonian (48), “microsaurs” into the Brigantian (49), and Crassigyrinus into the Tournaisian (this paper). Dating is according to the study by Gradstein et al. (20). Ad, adelogyrinids; Am, amiotes; An, anthracosaurs; Ai, aïstopods; Ba, baphetoids; BB, Blue Beach; Bm, Burnmouth; BmF, Burnmouth foot; Ca, Casineria; Co, colosteids; Cr, Crassigyrinus; Di, diadectids; EK, East Kirkton; Ge, gephyrostegids; Mi, microsaurs; Ne, nectrideans; Se, seymouriamorphs; Te, temnospondyls; Wh, whatcheeriids; WH/Db, Willie's Hole/Dumbarton.