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other dinosaurs or other already-dead, ready-to-eat meals? Did any dinosaurs ever
succumb to the evolutionary taboo of cannibalism by eating—or at least biting in-
to—their own kind?
All of these are behaviors about which we might otherwise speculate if not for
trace fossils becoming more pieces in the puzzle and completing pictures of how
dinosaurs lived their daily lives.
It's Only a Flesh Wound
Through the power of trace fossils, paleontologists can tell by looking at a dino-
saur's body that another dinosaur attacked it. Yet, as is typical in science, such dra-
matic interpretations can be equivocal. Such a quandary is exemplified by a 2013
discovery of fossilized dinosaur skin from South Dakota. Although this “skin” was
actually just a natural cast of the original skin, it was closely associated with the
bones of
Edmontosaurus annectens
, a Late Cretaceous hadrosaur from the western
U.S. and Alberta, Canada. Yet the skin itself is not the trace fossil. Instead, a prob-
able trace fossil is
in
the skin. Whether this trace fossil was made by the hadrosaur
or inflicted by another dinosaur, though, is subject to vigorous debate, as explained
here.
Owing to their rarity, dinosaur skin impressions give paleontologists good
reason to celebrate such finds. These unusual body fossils were normally formed
first as impressions against soft sediment, and then naturally cast in sandstone, sim-
ilar to how many dinosaur footprints were preserved. (Along those lines, the best-
preserved dinosaur tracks have scale impressions, but these are the marks of liv-
ing skin, not the skin itself.) This particular patch of skin had an irregular feature
which paleontologists interpreted as an apparent healed injury. This interpretation
provoked a spirited discussion about what constitutes good trace fossil evidence for
a dinosaur attacking another dinosaur.
Theskinimpressionandtheirregularityontheskinaresurprisinglysmall.The
patch of skin measures only about 12
X
14 cm (4.7
X
5.5 in), about the size of a
notebook that can fit in a shirt pocket. The oddity on that patch stands out from the