Another in the series of abstracts. This was my abstract for the think-tank conference at the Konrad Lorenz Institute in Vienna, Austria in September 2010. These are invite-only sessions on various hot topics related to evolutionary biology. Ours was on the "Constraints and Evolution of Form" - basically an Evo Devo related gig. I was the resident biomechanist for this one.
Emergence of convergent forms under fluid load in plants and animals
Very few biomechanists examine both plants and animals in parallel, apparently under a tacit assumption that the rules of shape determination must differ substantially between such distantly related groups. However, convergent structures suggest that the rules of shape governing these groups are largely the same. Such similarities suggest that environmental constraints are important in determining shape, and/or that genomes are more plastic and prone to morphological convergence than often accepted. I suggest that reference to physical first principles should be made whenever shape is examined in multi-cellular organisms, regardless of their phylogenetic position. As a case example, I report on the presence of highly convergent structures related to resistance and passive yield under aerodynamic fluid load in plants and animals. I utilize examples from both living and fossil forms, including broad-leafed trees, neornithine birds, and azhdarchid pterosaurs.
Showing posts with label Biomechanics. Show all posts
Showing posts with label Biomechanics. Show all posts
Monday, May 21, 2012
Sunday, May 20, 2012
Frogmouth Pterosaurs
I have (finally) some new material to post. In addition to the new stuff, I've decided to post some of my past abstracts that might not have been easily accessible to everyone. Here is my abstract from the GSA Northeast Conference in 2011. I gave a platform talk on the biomechanics of anurognathids (some of you will already know that Mark Witton and I have a manuscript nearing completion on the topic, as well).
Functional Morphology of Anurognathid Pterosaurs
Anurognathid fossils include several exceptionally well-preserved specimens, some of which include extensive soft tissue preservation. This exceptional amount of morphological information makes anurognathids prime candidates for functional biomechanical analysis. Furthermore, anurognathids displayed a suite of unusual characteristics that make them of particular interest for functional study. These traits included extensive pycnofiber coverings, fringed wing margins, shortened distal wings, shortened faces, and enlarged orbits. Prior authors have suggested that anurognathids were adapted to catching small insects on the wing. I present a quantitative analysis that supports this general behavioral inference, and provides details regarding probable anurognathid locomotion. Results indicate that anurognathids were exceptionally maneuverable animals.
Bone strength analysis in Anurognathus ammoni reveals that each proximal wing was capable of supporting nearly 22 body weights of force. The wing spar of A. ammoni was substantially stronger in bending than that of an average bird of the same size (residual of 0.72). The calculated relative bone strength overlaps significantly with that of living birds that capture prey on the wing (p>0.92) but differs significantly from all other avian morphogroups (p<0.04). Overall humeral robustness is similar between A. ammoni and megadermatid bats.
Anurognathid launch appears to have been particularly rapid and steep. Once airborne, anurognathid pterosaurs could likely generate high lift coefficients. Leading edge structure in Jeholopterus suggests that anurognathids were capable of generating a leading edge vortex (LEV) as observed in some living bats and swifts. Analysis of flapping efficiency suggests that the expansion of the proximal wing, coupled with reduction of the distal wing elements, would have increased flapping power at the cost of increased drag. The proportions of the wing and details of the shoulder may be indicative of the ability to hover for brief intervals; power analysis also supports this conclusion. These results are consistent with reconstructions of anurognathids as highly maneuverable flyers, preferentially foraging in cluttered habitats on small aerial prey.
Functional Morphology of Anurognathid Pterosaurs
Anurognathid fossils include several exceptionally well-preserved specimens, some of which include extensive soft tissue preservation. This exceptional amount of morphological information makes anurognathids prime candidates for functional biomechanical analysis. Furthermore, anurognathids displayed a suite of unusual characteristics that make them of particular interest for functional study. These traits included extensive pycnofiber coverings, fringed wing margins, shortened distal wings, shortened faces, and enlarged orbits. Prior authors have suggested that anurognathids were adapted to catching small insects on the wing. I present a quantitative analysis that supports this general behavioral inference, and provides details regarding probable anurognathid locomotion. Results indicate that anurognathids were exceptionally maneuverable animals.
Bone strength analysis in Anurognathus ammoni reveals that each proximal wing was capable of supporting nearly 22 body weights of force. The wing spar of A. ammoni was substantially stronger in bending than that of an average bird of the same size (residual of 0.72). The calculated relative bone strength overlaps significantly with that of living birds that capture prey on the wing (p>0.92) but differs significantly from all other avian morphogroups (p<0.04). Overall humeral robustness is similar between A. ammoni and megadermatid bats.
Anurognathid launch appears to have been particularly rapid and steep. Once airborne, anurognathid pterosaurs could likely generate high lift coefficients. Leading edge structure in Jeholopterus suggests that anurognathids were capable of generating a leading edge vortex (LEV) as observed in some living bats and swifts. Analysis of flapping efficiency suggests that the expansion of the proximal wing, coupled with reduction of the distal wing elements, would have increased flapping power at the cost of increased drag. The proportions of the wing and details of the shoulder may be indicative of the ability to hover for brief intervals; power analysis also supports this conclusion. These results are consistent with reconstructions of anurognathids as highly maneuverable flyers, preferentially foraging in cluttered habitats on small aerial prey.
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