Abstract: Four specimens of the pterosaur Pteranodon exhibit patterns of irregular alternating light and dark bands on the lateral surfaces of the upper jaw anterior to the nasoantorbital fenestra. Examinations reveal that the maxilla and premaxilla of Pteranodon consisted of two thin sheets of bone interconnected by regularly spaced septa with the spaces contained within presumably pneumatized, resulting in a structure analogous to modern honeycomb sandwich panels. The alternating light and dark bands resulted from waves of bone deposition moving anteriorly along the external surface of the lateral sheet of bone and laying down thin laminae of new bone while bone was simultaneously resorbed from the internal surface of the lateral sheet to maintain its thickness. The specimens that exhibit the bands were immature males and no banding was found in mature specimens or immature females. Therefore, the presence of the bands in immature males is interpreted as correlated with the enlargement and reshaping of the rostrum as males approached and attained sexual maturity.

Abstract: Three associated incomplete wing bones of a large pterodactyloid pterosaur from the Ferron Sandstone Member of the Mancos Shale Formation of Utah are described. Based on the morphology of the bones’ articular ends, the specimen is referred to the Pteranodontoidea. Associated ammonites indicate that the specimen’s age is Middle Turonian, so it adds to the sparse worldwide record of Turonian pterosaurs. The record of pteranodontoid pterosaurs in the Western Interior Seaway of North America is reviewed, and it is suggested that pteranodontoids were not diverse.

Abstract The musculature of the pectoral region of representative rhamphorhynchoid ( Campylognathoid.es ) and large pterodactyloid ( Anhanguera ) pterosaurs was reconstructed in order to examine the function of various muscles and the functional consequences of the evolution of the advanced pectoral girdle of large pterodactyloids. The reconstructions suggest that m. supracora-coideus was not an elevator of the wing, but instead depressed and flexed the humerus, m. latissimus dorsi, m. teres major, m. deltoides scapularis, and m. scapulohumeralis anterior were wing elevators. Comparison of the origin, insertion and function of muscles in the rhamphorhynchoid and the large pterodactyloid suggests that the evolution of the advanced pectoral girdle: (1) straightened the pull of m. pectoralis, m. deltoides scapularis and m. teres major, improving their function in wing elevation; (2) allowed ligaments rather than muscles to resist the tendency of those muscles to move the scapula; and (3) braced the pectoral girdle against the vertebral column so that the tendency of m. latissimus dorsi and of aerodynamic lift on the wing to move the scapulocoracoid medially and dorsally, thereby compressing the thorax, could be resisted. The osteological and myological complexity of the advanced pectoral girdle, its uniqueness among tetrapods and its association with other complex osteological features argue that the advanced pectoral girdle is a synapomorphy complex of a single clade of large pterodactyloids, rather than a mere correlate of large size evolved convergently in various lineages.