Meeting Abstract

P3.50  Jan. 6  Proportional and cross-sectional analysis of the forelimb skeleton in birds I: Pelecaniformes and Procellariiformes RASMUSSON, E. L.*; O’CONNOR, P. M.; Ohio Univ, Athens; Ohio Univ, Athens er238604@ohio.edu

Whereas previous research has documented how whole wing parameters such as wing loading and aspect ratio correlate with flight style, fewer studies have examined how forelimb skeletal morphology varies within clades that exhibit divergent locomotor behaviors. The objectives of this study were to conduct intralimb proportional and cross-sectional geometric analyses of the forelimb skeleton in two groups of distantly related birds. Morphometric data were collected on 12 pelecaniform and 12 procellariiform species. Basic metric (n = 122; e.g., length) and cross-sectional (n = 10; K value) data were collected on skeletal elements comprising the three forelimb segments. In the proportional analysis, pelecaniforms exhibit more variation in brachial and antebrachial length, whereas procellariiforms show more variation in carpometacarpal length. Moreover, cross sectional properties also vary within and between taxa and flight modes. For example, pelicans exhibit relatively thinner humeral cortices (K = 0.86) than either the within clade cormorants (K value=0.72) or the distantly related albatrosses (K value=0.71), suggesting a possible functional contrast between static soaring (pelican) and either flapping (cormorant) or dynamic soaring (albatross). In contrast, humeral circularity indices (HCI) may track both functional and phylogenetic influences, with the pelican (HCI = 0.87) and cormorant (HCI = 0.88) having a relatively more circular cross section than the dynamic soaring albatross (HCI = 0.72). These data suggest that forelimb skeletal morphology does not merely reflect phylogeny, but records a functional signal related to differential flight mode.