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the western U.S. and Canada. Ceratopsian tracks can be identified from their size,
numbers of digits—five on the front foot and four on the rear—and are preserved
inrocksthesameageasthosewithceratopsian bones.Thesesametracksalsoshow
that ceratopsians walked with an upright posture. This implies that these dinosaurs
couldmovemoreefficientlythanpreviouslysupposedfromskeletalevidence:more
like a rhinoceros, and less like a lizard.
Did large ceratopsians like
Triceratops
trot or gallop? We don't know for sure
yet, but their tracks would provide one of the best ways to test whether they moved
fasterthanawalk.SoeventhoughIonlyimaginedtwoceratopsianstrottingtoward
one another and knocking heads, it's feasible that someone could find tracks show-
ing that such fights did indeed happen. Moreover, this possible future discovery is
givenhopebecauseothertracefossils—thehealedwounds—suggestthatceratopsi-
ansoccasionallybecamecrosswithoneanother,whetheroverterritory,mates,food,
or all of the above.
Was there ever a dinosaur stampede like the one described, composed ofa mix
of diminutive dinosaurs and different species? Maybe, although this is now being
disputed.IntheCretaceousPeriod,about95millionyearsagoandonalakeshorein
what is now Queensland, Australia, nearly a hundred small, two-legged dinosaurs
ran in the same direction and at high speed. Paleontologists who originally studied
this tracksite think that species of theropods and ornithopods were together in the
same limited space. Evidently, they were then panicked by the arrival of a much
larger dinosaur on the scene. These tracks also say something about different spe-
cies of dinosaurs tolerating one another in the same environments, as well as react-
ing to the same stimuli. And just what was the identity of the large dinosaur that
caused such distress? And was it really a stampede, or can this unusual tracksite be
explainedbyothermeans?That'sastoryinitself,which,alongwiththesciencebe-
hind it, I'll gladly discuss later.
How about the scene with the swimming dinosaurs? Once again, trace fossils
confirm a concept that has gone back and forth among paleontologists, but is now
