. Bulletin. Natural history. s \. C' \ o Z- \ \ D' r v\ \ fig. 37. Diagrammatic representation of foreiimb movement in Dimetrodon as proposed by Watson (1917a). From left to right: lateral, anterior and ventral views. A, A', A" represent the start of the propulsive stroke; D, D', D" the completion of the propulsive stroke. H, humerus; R & U, radius and ulna. 1940: 138). His evidence for such a division—a slight ridge on some humeri and a contraction in the outline of the glenoid—is dubious at face value and since no func- tional explanation is given, the concept renders the screw
. Bulletin. Natural history. s \. C' \ o Z- \ \ D' r v\ \ fig. 37. Diagrammatic representation of foreiimb movement in Dimetrodon as proposed by Watson (1917a). From left to right: lateral, anterior and ventral views. A, A', A" represent the start of the propulsive stroke; D, D', D" the completion of the propulsive stroke. H, humerus; R & U, radius and ulna. 1940: 138). His evidence for such a division—a slight ridge on some humeri and a contraction in the outline of the glenoid—is dubious at face value and since no func- tional explanation is given, the concept renders the screw-shaped glenoid even more enigmatic. Moreover two separate surfaces, as proposed by Romer, would virtually prohibit any movement but simple abduction and adduction. Anteroposterior move- ment is prohibited by the interference of adjacent facets. I conclude from an examina- tion of well-preserved humeri and glenoids that there is no reliable evidence of sepa- rate facets and that, as will be shown in detail below, the complex morphology of the screw-shaped glenoid and spiral humeral head are related to diverse functional require- ments of a single articular joint. Miner (1925: 165-168) described in detail the glenohumeral articulation in Eryops. According to his interpretation the humeral head articulates with the poste- riorly facing, anterior half of the glenoid when the humerus is in its posterior position. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Peabody Museum of Natural History. New Haven, Peabody Museum of Natural History, Yale University
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