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by spring run-off of melt waters. Moreover, the physical sedimentary structures as-
sociated with the trace fossils—ripple marks and cross-bedding—also indicated a
healthyflowofwater.Thesestructureswouldhavemorelikelyformedduringapo-
lar spring or summer following snow melts.
Along those lines, I had published a paper in 2009 about physical sedimentary
structures—such as ripple marks, mudcracks, and so on—and traces—such as in-
vertebrate burrows and vertebrate tracks—next to the Colville River on the North
Slope of Alaska. Hence, the rocks in front of us, when combined with what I had
learned from that Alaskan riverbank a few years beforehand, almost acted like a
time machine. The Cretaceous rocks of Australia and the modern sediments of
Alaska could be compared as polar ecosystems, despite being separated by more
than 100 million years and thousands of kilometers.
Yetanotherjustificationformygrowingelationwasthattheseburrowsclosely
resembled trace fossils I had seen in rocks at another place: Knowledge Creek, just
a few kilometers east of us. Knowledge Creek is the place where the only well-
documenteddinosaurtrackfromtheEumerallaFormationwasdiscovered.In1980,
a little more than thirty years before Tom, Greg, and I stepped foot on Milanesia
Beach together, Tom and Pat Vickers-Rich found this track. It was probably made
byasmallornithopoddinosaur,whichwasnotsurprisingtothem,seeingthatnearly
all of the skeletal remains of dinosaurs in Victoria belonged to such dinosaurs.
I had visited Knowledge Creek three times in recent years—2006, 2007, and
2009—but did not find any other definite dinosaur tracks there, only a few vague
outlines. Still, I was lucky enough to have discovered possible dinosaur burrows
and invertebrate trace fossils there, the latter nearly identical to the ones we were
seeingthatmorningatMilanesiaBeach.Similarsedimentaryrocksandtracefossils
at Knowledge Creek and Milanesia Beach implied that similar environments had
produced these rocks. So perhaps the conditions at both places were conducive to
dinosaurs walking across floodplain surfaces, allowing their tracks to get preserved
well enough that they would be identified some day.
