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have been living in burrows of their own making. He did not present much data
to support this supposition—like, say, trace fossils of their burrows—but instead
based it on how these dinosaurs were little and some of their carnivorous contem-
poraries were big. Thus, burrowing would have been a great way for these cute, in-
nocent herbivores to avoid getting chomped by nasty, ravenous predators. Bakker
mentioned this idea of burrowing ornithopods in a 1996 paper, and promoted it in
talks afterwards.
As mentioned earlier, digging was proposed as early as 1985 to explain sauro-
podfeet,whichwasconfirmedabouttwodecadeslaterbytheirnests.
Troodon
nests
found in the 1990s also showed that some dinosaurs could dig. Based on their ana-
tomies, the small theropod
Mononykus
was mentioned as a possible burrowing di-
nosaur, as was the small ornithopod
Heterodontosaurus
. However, for
Mononykus
,
its forearms seemed too short to do much more than break up soil.
Sure, all of this talk about whether dinosaurs lived underground or not is very
interesting, but runs the risk of becoming an esoteric subject that is only appreci-
ated by the most dedicated of dinosaur fan-boys or fan-girls. Ultimately, one has to
askthatmostunderusedbutinstructiveofquestionsinscience:Sowhat?Otherthan
being able to exclaim “We got ourselves a burrowing dinosaur! Yee haw!” what
meaning did such a discovery have in a much larger sense, relating to the Mesozoic
world and modern times alike?
Here is one word that should warrant sitting up and paying attention: extinc-
tion. As discussed earlier, most scientists now accept that a large meteorite hit the
earthabout65
mya
,landingintheareaofwhatisnowtheYucatanPeninsula.Apart
from those that died from the direct hit, this impact likely had dire consequences
worldwide for life in the oceans and on land, including a dust cloud—mixed with
sootfromforestfires—thatwouldhaveblockedoutsunlightforseveralyears.Take
away sunlight and terrible things happen to most ecosystems. For example, many
photosynthesizing algae in Cretaceous oceans were adapted to full sun year-round,
as well as land plants that grew and reproduced best when illuminated. Most of
