Meeting Abstract
104.4 Tuesday, Jan. 7 08:45 From wing to bone: Anatomy and microanatomy of skeletal correlates for whole wing shape in Neornithine birds HIERONYMUS, TL*; SIMONS, ELR; NEOMED; Midwestern University thieronymus@neomed.edu
Bird wings display a remarkable variation of shape and size, ranging from small, rounded wings in sparrows to long, narrow wings in albatross. This variability occurs hand-in-hand with adaptive differences in flight behavior. Our ability to reconstruct the evolutionary history of wing shape in birds is hampered by this same variability. The high rate of change that underpins variability also leads to ambiguous ancestral character state reconstructions for the Paleogene stem lineages of extant neornithine birds. Understanding trends and patterns in the evolution of bird flight requires reliable skeletal correlates of wing shape, which will allow fossils to anchor ancestral character state reconstructions in deep time. We examined skeletal correlates for the attachment of remiges, which determine the majority of wing area and shape, by dissection and μ CT (n=35 species), coupled with histological preparations of skeletal elements and associated soft tissues (n=6 spp). We found six skeletal characters to be directly related to ligaments of feather attachment. We examined the relationship between these characters and aerodynamically relevant wing shape variables (body mass, wing span, and wing area) in extant birds (n=71 spp) using a phylogenetic adaptation of Distance-Based Redundancy Analysis (db-RDA). The resulting ordination defines a morphospace of skeletal correlates, which is constrained by robust relationships to aspect ratio and wing loading. The Cretaceous stem ornithurine Ichthyornis shows skeletal correlates of high aspect ratio and low wing loading, in sharp contrast to the “average” values inferred for the neornithine crown node from extant data alone. Our results highlight how quantitative models of soft-tissue morphology that include fossil data can dramatically influence reconstructions of evolutionary pattern and process.
