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3-D track formation analysis with X-rays

From: Ben Creisler

New in Palaeontologia Electronica:

Richard G. Ellis and Stephen M. Gatesy (2013)
A biplanar X-ray method for three-dimensional analysis of track formation.
Palaeontologia Electronica 16 (1); 1T, 16p;

Tracks arise through a complex interplay between animal and substrate.
Studying this dynamic process is challenging because most
foot-sediment and sediment-sediment interactions are rapid and hidden
from view. Herein, we describe a new method for visualizing and
quantifying three-dimensional movements of both a morphologically
accurate indenter and realistic sediment during track formation. Our
method uses biplanar X-ray imaging and an animation-based workflow to
reconstruct the trajectories of metal beads seeded throughout the
sediment volume. X-rays allow sub-surface motion normally concealed by
the foot and opaque matrix to be analyzed at 30 frames per second with
sub-millimeter resolution. Results from two case studies of tridactyl
tracks in semi-liquid mud provide novel, animated visualizations,
examples of ensemble and particle-specific data, as well as measures
of precision and accuracy. This methodology has the potential to
mechanistically link specific track morphologies to foot movement,
clarify undertrack formation, validate computational models, and set a
new standard for evidence-based reconstruction of locomotion from
fossil footprints.