Geoscience Reference
In-Depth Information
All of these bits of knowledge then become handy forensic tools for figuring out
who ate whom. So this is exactly how three paleontologists—Ray Rogers, David
Krause, and Kristi Rogers—discerned that
Majungasaurus
, a large theropod from
Late Cretaceous rocks of Madagascar, was a cannibal. In one specimen of
Majun-
gasaurus
,itsribsandvertebraehadtoothmarksonthem,andratherdistinctiveones.
The toothmarks were a series of thin, evenly spaced grooves caused by serrations,
ones that perfectly matched those on the teeth of
Majungasaurus
. These grooves
werealsoseparatedbyagapthatcorrespondedwiththeintertoothdistanceof—you
guessed it—
Majungasaurus
.
Based on similar toothmarks these paleontologists had seen on sauropod
bones, they knew that this theropod normally ate those dinosaurs. But at least one
decided its dead relative looked too appealing to pass up as a snack. Based on the
bodily locations of the toothmarks, the
Majungasaurus
must have been dead when
they were made, so these trace fossils are not only of cannibalism but also of scav-
enging.Suchevidenceisabitperplexing,leadingpaleontologiststowonderifthere
was a time when ecological conditions during the Late Cretaceous in Madagascar
became bad enough that large theropods resorted to eating their own.
From an evolutionary standpoint, one might think that cannibalism is uncom-
mon in modern large carnivores. After all, any long-term reliance on consuming
your own species could lead to eventual extinction. Yet cannibalism happens. Ko-
modo dragons, crocodilians (including alligators), big cats such as lions and tigers,
andbearsareamongthelargepredatorsthatwilleattheirownspecies.Somecanni-
balism is a consequence of competition, in which a male lion kills and eats the cubs
of a rival male, or bad timing, such as when a baby alligator swims too close to a
hungry adult. But cannibalism also can be more opportunistic, such as during hard
times; when you're starving and nothing else is around, you might as well eat your
brother. This situation is especially more likely to take place during times of eco-
logical stress, when food supplies tend to shrink. Think of droughts, which cause
many plants to wither and die, negatively impacting herbivores, which would in
