Comparative Paleobiomechanics of Holdfasts in Soft Substrates

University Of Illinois At Chicago, Chicago IL

Investigators

Abstract

Comparative Paleobiomechanics of Holdfasts in Soft Subtrates Roy Plotnick, University of Illinois, Chicago This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The root systems of terrestrial plants not only obtain nutrients and water, but provide critical physical support for the above ground portions of the plants. Some modern marine organisms, including algae and invertebrates, also have anchoring systems or holdfasts. This is especially important for organisms living on unconsolidated sediments, such as sandy or muddy seafloors, from which they can be uprooted by waves or current. Many fossil organisms also have structures that have been interpreted as holdfasts. Some of these structures resemble plant roots, whereas others resemble ship anchors or grapnels. Although the mechanics of tree roots have been well studied, there has been very little done on the holdfast systems of either fossil or recent marine animals on soft substrates. Previous studies of fossil holdfasts have either been detailed verbal descriptions of their morphology or qualitative interpretations of their function. The goal of this project is to examine the shape and engineering design (biomechanics) of holdfasts in these extinct forms and in living analogs, to determine if there are underlying commonalities or multiple alternative solutions to the problem of how ?not to go with the flow.? The proposed project has two major components. The first of these will be the quantitative description of the morphology of the holdfast systems of modern and fossil invertebrates. This will be based on an examination of specimens in museum collections. The second component will be experimental studies of alternative holdfast designs. This will include the construction of models based on actual specimens of holdfasts, as well as models that represent variability in key parameters believed to control their ability to resist dislodgement. These models will be subject to measured removal forces and their resistance to these forces will be compared. These results will allow direct testing of hypotheses for function in holdfasts in fossil forms.