Geoscience Reference
In-Depth Information
have made their nests in trees, just like modern birds. However, until we have some
evidence for these, we can only speculate.
For those people who might wonder how to tell a hole in the ground from,
well, other things, how would someone recognize a dinosaur nest in the fossil re-
cord? Fortunately, paleontologists who have interpreted the few indisputable dino-
saur nests in the geologic record made a nice little checklist for the rest of us to fol-
low,whichhelpsconsiderably.Hereisasummaryofthatlist,butposedasquestions
to ask when encountering a depression in a Mesozoic rock that might be a dinosaur
nest:
1. Does the depression cut through any layered sedimentary rock below it?
This is an especially good question to ask when investigating whether the
rock that preserves a potential nest has different colors and grain sizes than
the sediment above it. For example, the sediment below the depression
might be a green rock mostly made of mud (mudstone), whereas the sedi-
ment filling it might be a red rock composed of sand (sandstone).
2. Does the depression hold lots of entire (or nearly entire) eggs, along with
skeletons of baby or otherwise young dinosaurs, and all of the same spe-
cies? Be careful with this one, though. As mentioned before, eggs can be
transportedfarawayfromwhereamotherdinosauroriginallylaidhereggs,
meaning such a depression might simply be where these eggs and skeletal
remains accumulated after being washed about by currents.
3. Doesthedepressionalsohavearaisedrimaroundit,accentuatingitsbasin-
like appearance? A related question to ask is, is this rim also made of sedi-
ment differing from what is underneath or outside of it? These rims would
have served an important primary purpose, such as preventing rounded
eggs from rolling away as a mother dinosaur laid them.
4. Does the rock filling in the depression and covering the rim have its own
distinct traits, like different colors and textures (mentioned before), bed-
ding, or insect burrows and cocoons? Such features might hint of a fossil
soil(paleosol),whichwouldtellpaleontologiststhatthedepressionwasex-
posed at the ground surface before being covered, as opposed to, say, at the
bottom of a river.
