| dc.description.abstract | The avifauna of the Early Cretaceous is composed of a unique combination of primitive and derived forms. Primitive birds with long tails are found preserved in the same strata as modern-type ornithurine birds, the primitive, beaked confuciusornithids, a unique side branch of Aves, and the diverse but extinct enantiornithines. There have been few studies on the trace fossils they produce, detailed reconstruction of soft tissues, or the morphology of their feet and hindlimbs. Furthermore, there are few studies of modern bird feet and hindlimbs for comparison. This dissertation examines bird tracks from the Lower Cretaceous Haman Formation of the Republic of Korea, avian body fossils from the Lower Cretaceous Jehol Group in northeastern China, and the feet and hindlimbs of modern birds for comparison with Early Cretaceous avian fossils. Also studied are the effects of sediment grain size and media water content on the production of traces (i.e., track morphology and bird behavior) by the domestic chicken (Gallus gallus) and Mourning Doves (Zenaida macrocura). Early Cretaceous ornithurine avian behavior was already strikingly advanced and included multiple types of feeding behaviors identical to those performed by modern birds. The ichnodiversity of ornithurines was much higher than the body fossil record suggests. Retrodicting what types of tracks certain types of fossil birds would have produced is possible due to a nonsignificant difference (p-value > 0.05) between the soft-tissue toe length and the osteological toe length in birds. Toe width is significantly different, however, neoichnological experiments show that toe width is strongly influenced by media consistency and, therefore, is not a reliable measurement in avian ichnology. The hindlimb of birds has clearly shifted through time with function, as the femur contributed less to hindlimb motion. Under laser fluorescence, 0.05) between the soft-tissue toe length and the osteological toe length in birds. Toe width is significantly different, however, neoichnological experiments show that toe width is strongly influenced by media consistency and, therefore, is not a reliable measurement in avian ichnology. The hindlimb of birds has clearly shifted through time with function, as the femur contributed less to hindlimb motion. Under laser fluorescence, Confuciusornis is shown to have possessed soft tissues identical to modern birds, and the primary and secondary feather morphology is much rounder than previously interpreted. Neoichnological studies further support the early evolution of modern avian behavior and erect quantification criteria for modern and ancient bird behaviors. This dissertation represents important progress in our understanding of how avian foot morphology and behavior has evolved through time. | |
