Geoscience Reference
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almost exclusively? Check. Was I an idiot? Check. But I was pretty damned de-
lighted to be one in this instance.
Dave's message had more to say, including a brief confession of his long-
held suspicion that other small dinosaurs such as “hypsilophodonts”—a non-clade
grouping of small ornithopod dinosaurs—might have burrowed. This informed
guess was based on his observation of the small Late Cretaceous hypsilophodont
Orodromeus
near his
Troodon
nest sites in northwestern Montana. In more than a
few specimens, Dave had noticed that the
Orodromeus
skeletons were unusually
complete and concentrated in compact masses, encased in well-cemented rocks.
The simplest explanation for this unusual preservation, he thought, was that these
small herbivorous dinosaurs might have been in chambers at the ends of those bur-
rows, then either were buried after dying or buried alive in their burrows. Nonethe-
less, he had no other evidence for this idea, such as an actual burrow connecting to
these masses of bones. So it remained just a nagging conjecture awaiting more per-
suasiveevidence.Andnowhehadit:aprobableburrow,attachedtoaprobablebur-
row chamber which held the body fossil of its possible maker, which just happened
to be a hypsilophodont dinosaur. The last paragraph in Dave's message neatly sum-
marized and resonated with my feelings at the time:
Obviously … some interpretation is dependent upon the actual specimen
within … but still … a cool specimen. I think that really only hypothesis
1 and 2 are suitable
. The sequence includes paleosols not too unlike the
Egg Mountain area.
When he referred to “hypothesis 1 and 2,” he meant what I had enumerated
previously: (1) a large burrow that had the burrow-maker at one end, which in this
instance was a dinosaur; and (2) a large burrow with a dinosaur at its end, but one
that was not the maker of the burrow. In this second scenario, the dinosaur could
have lived in the abandoned burrow of another unknown animal—dinosaurian or
otherwise—or had its remains washed into the burrow where they were subse-
