Geoscience Reference
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to gain access to their goodies, sort of like a dinosaurian anteater. Moreover, one
specimen of the Early Cretaceous ceratopsian,
Psittacosaurus
, was found with 34
juveniles just like it, all collected in a bowl-like depression. Paleontologists specu-
lated that all of these animals may have died together in a collapsed burrow, but no
one could tell for sure if this is what happened, nor whether or not the adult made
the depression.
More recently, in 2010, trace fossils attributed to predatory dromaeo-
saurs—such as
Deinonychus
—were interpreted as dig marks made by claws on
their rear feet as they tried to unearth small mammals, whose preserved fossil bur-
rowswerejustunderneaththesedigmarks.Buttheseandotherdinosaurswereonly
scraping the surface, so to speak. What about dinosaurs that went deeper and actu-
ally spent extended periods of time underground?
Before jumping into our time machines and going back to the Mesozoic Era,
a much better idea to ask ourselves first is what modern vertebrates might tell us
about burrowing behavior. After all, the variety of today's burrowing vertebrates
is astounding, ranging from lungfish to spadefoot toads to skinks, alligators, naked
molerats,puffins,aardvarks,andmore.Furthermore,justlimitingyourlisttomam-
mals that live part or most of their lives underground will result in hundreds of spe-
cies, and they range in size from Oldfield mice (
Peromyscus polionotus
) to grizzly
bears (
Ursus arctos
).
Thereisnomysteryaboutwhysomanyvertebratesburrow,either,withanum-
ber of perfectly fine evolutionarily based reasons to excavate a home and live in
it. For one, parents can raise their young in a safe, quiet place, away from the pry-
ing eyes and noses of predators. In upland environments, where undergrowth and
trees constitute fuel for wildfires, burrows act as shelters from those natural hazar-
ds. Burrows also maintain equitable temperatures year-round. Thus, in places with
extreme daily or seasonal fluctuations in temperatures—especially in deserts or po-
lar regions—burrows are not too hot, not too cold, but just right. For a few anim-
als, suchaslungfish orsome toads andturtles, these burrowsserve asaestivation or
