Geoscience Reference
In-Depth Information
insideofthetracks,butjoggingresultsinridges,mounds,andplatesofsandcaused
by each foot as it pressed against the sand. Sprinting imparts more prominent struc-
tures,andmaybesandkickedcompletelyoutofthetrack.Inotherwords,tracksand
these structures caused by the applied and released pressure—which some track-
ers call
pressure-release structures
,
pressure releases
, or
indirect features
—can be
applied as another type of speedometer and used as independent checks of relative
stride lengths.
Thesestructures,however,dependonmanyfactorsfortheirformationandpre-
servation,suchasthetypeofsediment(mud,sand,pebbles?),moisturecontent(dry,
slightly moist, saturated?), packing (loose sand, hard-packed sand?), slope angle
(flat surface, heading uphill, going downhill?) and not just the speed of the track-
maker. Imagine if a theropod ran across moist and slippery mud, and then dry sand;
then visualize how different its tracks would look in each type of sediment. Add in
little behavioral nuances such as head position (up, level, down, right, left?), turn-
ing to one side or another while moving, stopping to scratch its back, or bending
down to nab a small mammal with its mouth. All of these factors culminate in what
paleontologistsconsideras“tracktectonics,”miniaturelandscapeswroughtbyadi-
nosaur's foot pushing or twisting against a muddy or sandy medium.
Another important factor in the formation of such structures around a track is
the size and anatomy of the trackmaker's feet. For instance, think of how a saur-
opod's elephant-like foot made far different structures compared to the foot of a
small, thin-toed theropod. This all means that tracks can be quite complicated; and
tobetterunderstandthem,theyarethesubjectofmuchexperimental workwithreal
animals (more on that later) and three-dimensional computer simulations. In con-
trast, drawing a simple cartoon outline of a track would be like summarizing a Sal-
vador Dali painting as “art,” a terrible misdeed that omits all of its colors, hues,
gradations of tones, and themes. What a pity to miss all of those metaphorically
melted watches.
