Page:The Osteology of the Reptiles.pdf/176

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Fig. 129. Theromorph limbs: Naosaurus, humerus, dorsal side, femur, ventral side. One half natural size.


The humerus (Figs. 129–131), or first bone of the anterior extremity, articulates in the glenoid fossa of the scapular girdle, usually by a more or less complete, free, ball-and-socket joint, permitting rotation. In most of the Cotylosauria (Figs. 128, 130, 132) and stouter-limbed Theromorpha (Figs. 129, 131, 134) the articular surface is more or less spiral-like, extending around the head from the ventral postaxial to the dorsal preaxial side, permitting movement in an antero-posterior direction with a concomitant partial rotation as the hand, directed forward obliquely, is brought backward in walking. The bone was not depressible below a horizontal plane without dislocation. The articular surface of the pterodactyl humerus