Cross Sectional Geometry of the Forelimb Skeleton and Flight Mode in Pelecaniform Birds
allometry; Anatomy & Morphology; aves; behavior; cross-sectional geometry; evolution; flight; functional-morphology; Locomotion; long bones; pelecaniforms; phylogenies; regression; size; variables
Avian wing elements have been shown to experience both dorsoventral bending and torsional loads during flapping flight. However, not all birds use continuous flapping as a primary flight strategy. The pelecaniforms exhibit extraordinary diversity in flight mode, utilizing flapping, flap-gliding, and soaring. Here we (1) characterize the cross-sectional geometry of the three main wing bone (humerus, ulna, carpometacarpus), (2) use elements of beam theory to estimate resistance to loading, and (3) examine patterns of variation in hypothesized loading resistance relative to flight and diving mode in 16 species of pelecaniform birds. Patterns emerge that are common to all species, as well as some characteristics that are flight-and diving-mode specific. In all birds examined, the distal most wing segment (carpometacarpus) is the most elliptical (relatively high I-max/I-min) at mid-shaft, suggesting a shape optimized to resist bending loads in a dorsoventral direction. As primary flight feathers attach at an oblique angle relative to the long axis of the carpometacarpus, they are likely responsible for inducing bending of this element during flight. Moreover, among flight modes examined the flapping group (cormorants) exhibits more elliptical humeri and carpometacarpi than other flight modes, perhaps pertaining to the higher frequency of bending loads in these elements. The soaring birds (pelicans and gannets) exhibit wing elements with near-circular cross-sections and higher polar moments of area than in the flap and flap-gliding birds, suggesting shapes optimized to offer increased resistance to torsional loads. This analysis of cross-sectional geometry has enhanced our interpretation of how the wing elements are being loaded and ultimately how they are being used during normal activities. J. Morphol. 272: 958-971, 2011. (C) 2011 Wiley-Liss, Inc.
Simons E L R; Hieronymus T L; O'Connor P M
Journal of Morphology
2011
2011-08
Journal Article
<a href="http://doi.org/10.1002/jmor.10963" target="_blank" rel="noreferrer noopener">10.1002/jmor.10963</a>
Cross-sectional bone distribution in the mandibles of gouging and non-gouging platyrrhini
bone biomechanics; callithrix-jacchus; cross-sectional geometry; form; functional-significance; iterative selection method; jaw functional morphology; load resistance; macaca-fascicularis; mandibular corpus; morphology; new-world monkeys; primates; stress; tree gouging; Zoology
Recent morphometric analyses have led to dissimilar conclusions about whether the jaws of tree-gouging primates are designed to resist the purportedly large forces generated during this biting behavior. We further address this question by comparing the cross-sectional geometry of the mandibular corpus and symphysis in tree-gouging common marmosets (Callithrix jacchus) to nongouging saddleback tamarins (Saguinus fuscicollis) and squirrel monkeys (Saimiri sciureus). As might be expected, based on size, squirrel monkeys tend to have absolutely larger cross-sectional areas at each tooth location sampled, while saddleback tamarins are intermediate, followed by the smaller common marmosets. Similarly, the amount and distribution of cortical bone in squirrel monkey jaws provides them with increased ability to resist sagittal bending (I (xx) ) and torsion (K) in the corpus as well as coronal bending (I (xx) ) and shearing in the symphysis. However, when the biomechanical parameters are scaled to respective load arm estimates, there are few significant differences in relative resistance abilities among the 3 species. A power analysis indicates that we cannot statistically rule out subtle changes in marmoset jaw form linked to resisting loads during gouging. Nevertheless, our results correspond to studies in vivo of jaw loading, field data, and other comparative analyses suggesting that common marmosets do not generate relatively large bite forces during tree gouging. The 3 species are like most other anthropoids in having thinner bone on the lingual than on the buccal side of the mandibular corpus at M-1. The similarity in corporal shape across anthropoids supports a hypothesized stereotypical pattern of jaw loading during chewing and may indicate a conserved pattern of mandibular growth for the suborder. Despite the overall similarity, platyrrhines may differ slightly from catarrhines in the details of their cortical bone distribution.
Vinyard C J; Ryan T M
International Journal of Primatology
2006
2006-10
Journal Article
<a href="http://doi.org/10.1007/s10764-006-9083-7" target="_blank" rel="noreferrer noopener">10.1007/s10764-006-9083-7</a>
Getting into Shape: Limb Bone Strength in Perinatal Lemur catta and Propithecus coquereli.
cross-sectional geometry; material properties; ontogeny; quadrupedalism; vertical clinging and leaping
Functional studies of skeletal anatomy are predicated on the fundamental assumption that form will follow function. For instance, previous studies have shown that the femora of specialized leaping primates are more robust than those of more generalized primate quadrupeds. Are such differences solely a plastic response to differential loading patterns during postnatal life, or might they also reflect more canalized developmental mechanisms present at birth? Here, we show that perinatal Lemur catta, an arboreal/terrestrial quadruped, have less robust femora than perinatal Propithecus coquereli, a closely related species specialized for vertical clinging and leaping (a highly unusual locomotor mode in which the hindlimbs are used to launch the animal between vertical tree trunks). These results suggest that functional differences in long bone cross-sectional dimensions are manifest at birth, belying simple interpretations of adult postcranial form as a direct record of loading patterns during postnatal life. Despite these significant differences in bone robusticity, we find that hindlimb bone mineralization, material properties, and measures of whole-bone strength generally overlap in perinatal L. catta and P. coquereli, indicating little differentiation in postcranial maturity at birth despite known differences in the pace of craniodental development between the species. In a broader perspective, our results likely reflect evolution acting during prenatal ontogeny. Even though primates are notable for relatively prolonged gestation and postnatal parental care, neonates are not buffered from selection, perhaps especially in the unpredictable and volatile environment of Madagascar. Anat Rec, 2018. (c) 2018 Wiley Periodicals, Inc.
Young Jesse W; Jankord Kathryn; Saunders Marnie M; Smith Timothy D
Anatomical record (Hoboken, N.J. : 2007)
2018
2018-12
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/ar.24045" target="_blank" rel="noreferrer noopener">10.1002/ar.24045</a>