Geoscience Reference
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turnaffect carnivores. Hence,thebiological tabooofcannibalism becomes lessofa
barrier when food becomes scarce.
So let's apply this idea to the geologic past. Did Late Cretaceous ecosystems
of Madagascar undergo any sort of stresses, such as droughts? Apparently so, as
its rocks show the region was semi-arid while dinosaurs lived there, but with pro-
nounced wet-dry cycles. Such environments were more susceptible to droughts
than, say, a tropical rainforest. One of the more compelling pieces of evidence for
droughts in this area during the Cretaceous comes from other trace fossils, namely
lungfish burrows.
Modern lungfish, to keep from drying out during times of low rainfall, make
burrows. They then reside in these while also enveloping themselves in slimy co-
coons,thusdoublingtheirprotection.Inanichnologicallywonderfulpaperbypale-
ontologists Madeline Marshall and Ray Rogers published in 2012, they interpreted
more than a hundred lungfish burrows in a Late Cretaceous river deposit in Mada-
gascar. These burrows, which were nearly identical to modern ones, pointed toward
this as a behavioral response to a long, dry time that required hunkering down. So
just like insect cocoons next to
Troodon
nests in Montana, these trace fossils tell us
something about how animals around dinosaurs were adapting to their climate. Did
such dry periods also affect food supplies of Late Cretaceous dinosaurs in Mada-
gascar? Perhaps, although paleontologists need more details before they can say for
sure.
Regardless of reasons why, finds of dinosaur-cannibal trace fossils from so
longagoareremarkableenoughtopromptpaleontologiststoreexaminetoothmarks
on theropod bones, checking to see whether or not these came from the same spe-
cies. From there, they could then test whether these behaviors were anomalous or
more normal than originally surmised.
Along those lines, trace fossils tell us that another large theropod, our old
friend
Tyrannosaurus rex
, decided to count on its relatives for some of its meals.
In a 2010 study conducted by Nicholas Longrich and three other paleontologists,
