Geoscience Reference
In-Depth Information
• Are these tracks undertracks, and if so, how far below the original surface
were they formed?
• Do you feel clueless yet? (Welcome to my world.)
Along these lines, three Spanish paleontologists—Josè Moratalla, Josè Sanz, and
SantiagoJimenez—triedtotakesomeofthisguessworkoutofdistinguishingthero-
pod and ornithopod tracks. In an article published in 1988, they used a sample of
66 Early Cretaceous tridactyl dinosaur tracks from Spain, all of which had been
identified confidently as either ornithopod or theropod tracks on the basis of their
qualities. With these tracks, they measured nearly every parameter they could ima-
gine: digit lengths, digit widths, angles between digits, widths of the foot between
digits, and more. Moratalla and his coauthors then compared ratios of these para-
meters—such as digit length:digit width—to see which ones were significantly dif-
ferent from one another (statistically speaking).
From these analyses, they figured out “threshold” values and probabilities for
some of the ratios and calculated probabilities of a ratio belonging to an ornitho-
pod or theropod. For instance, if the length:width ratio of a tridactyl track is above
1.25,or25%longerthanitiswide,thenthere wasan80%probability that thetrack
belonged to a theropod. Fortunately, they didn't just stop with the length:width ra-
tio. They also checked all other ratios to see whether these consistently show a high
probability of a theropod trackmaker or not, just to retest their initial identification.
With the publication of this study in 1988, dinosaur ichnologists had a quant-
itative checklist they could apply to three-toed dinosaur tracks. Of course, whether
alldinosaurichnologistsactuallyreadthispaper,applieditsmethods,ortestedtheir
applicability to dinosaur tracks other than the ones they studied is another matter.
Regardless, numbers produced by such a study also could be combined with non-
numerical observations to test whether or not a fearsome carnivore or a peaceful
herbivore had made a given series of three-toed dinosaur tracks. One example of
such an observation is whether a track has sharp clawmarks or not. This feature is
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