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above their intestines, where they served as digestive aids to grind varied omni-
vorous foodstuffs like internal mortars and pestles. These theropods were aware of
but mostly unperturbed by what was taking place upstream, as the “ Mononykus”
and Thescelosaurus groups were still far away from them. Their tracks, accented
by sharp claw marks, left vague outlines on the gravelly parts of the bar, but were
crisply defined on the sandier patches. The female tracks were only slightly larger
than those of the males, but otherwise identical in form.
Meanwhile, located between the Dromaeosaurus and the Struthiomimus , a
male-female pair of Ankylosaurus , joined in coitus, ignored just about everything
else happening around them. These heavily armored dinosaurs, each weighing
about five tons, typically would have left large, deep tracks regardless of what they
weredoing.Buttheadditionofthemale'sweighttotherearofthefemalemeanther
hind feet sank much deeper than his into the moist sand below. Together they made
a six-footed impression, the front four coming from her and two rear ones from his
hind feet. The earth moved, however briefly, for both partners.
Where the “ Mononykus” and Thescelosaurus once stood on the lower part of
thefloodplain,atleastafewoftheirtracksandsomeoftheirscathadbeensquashed
under the thumping feet of the older Triceratops as he closed the gap between him-
self and the younger male. The latter could no longer stay in one place and com-
menced walking, then trotting, toward the other. Snails, clams, and salamanders in
the floodplain sediments unlucky enough to be in the same place as a Triceratops
foot were summarily crushed.
The collision between the two male ceratopsian dinosaurs, which had a com-
bined weight of about twenty tons, was surprisingly subdued and dull. They did not
hitoneanotheratfullspeed,astheadditiveimpactwouldhavekilledbothinstantly.
Instead,theyfirststopped,andthenclashedtheirmightyheadstogether.Theirwide
headshieldsnotonlyservedasgreatbillboardsforattractingmatesandrecognizing
their species, but also dissipated much of the energy when they struck. Still, the left
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