Geoscience Reference
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another, each identified faster than the previous one. Within about ten seconds, I
realized the bumpy surface was loaded with dinosaur tracks.
One of these footprints—a chicken-sized one only about 7 cm (2.8 in)
long—was close to the edge of the slab. With my heart beating faster, I then did
something I almost never do with modern tracks, which was backtracking. I shifted
my focus behind the track nearest me to see if any similar ones preceded it. Sure
enough, there was another of the same size, aligned with the previous one. Hesit-
ating in disbelief, I backtracked one more time. Another track was exactly where it
shouldbe,atadistancenearlyidenticaltothespacebetweentheothertwo,although
slightly off the line of travel. One, two, three steps in sequence, with a slight right-
ward turn; it was a preserved motion from more than 100 million years ago, made
byasmalltheropoddinosauronariverfloodplainduringapolarsummer.Itwasthe
first known dinosaur trackway in all of southern Australia, and the first polar-dino-
saur trackway from the Southern Hemisphere.
There was no time to celebrate; I needed to get to work. I looked more closely,
feeling the rock surface. Then I began sketching what was there and marking loc-
ations of the tracks, using graph paper in my geological field notebook to make
a scaled drawing that served as a sort of “track map.” Unlike taking photographs,
drawing forced me to look at the rock and its fossil tracks repeatedly, carefully, and
critically, a time-honored observational technique I teach to my students.
This method soon paid off, for within about ten minutes I found a few more
tracks, subtle ones that either consisted of very faint toe impressions or were miss-
ing parts. This partial preservation of fossil tracks is typical. Most fossil tracks are
registered on surfaces below where the animal actually walked as undertracks, like
those made by a pen or pencil on an underlying sheet of paper. What then happens,
erosion wipes away the “true tracks” made on the uppermost surface, taking away
those footprints that may have shown skin impressions, toe pads, claw marks, and
minute movements of individual toes. This seemingly unfair erasure of information
means that the underlying impressions of a track have a better chance of making
