Geoscience Reference
In-Depth Information
assic rocks of western China were unwillingly ushered into the fossil record. In a
2009 journal article with the beguiling title of “Dinosaur Death Pits from the Juras-
sic of China,” the researchers—David Eberth, Xu Xing, and Julia Clark—proposed
that specimens of the small theropod
Guanlong wucaii
had fallen into 1 to 2 m
(3.3-6.6 ft) deep mud-filled pits made by large sauropods similar to the Late Juras-
sic
Mamenchisaurus
.
Guan-long
wasn't the only animal to suffer such a fate at the
feet of these sauropods, either, as the theropod
Limusaurus
and about twenty other
species were entombed in these tracks. What all of these dinosaurs had in common
was that they were small and bipedal, meaning they lacked sufficient limb strength
to yank themselves out of their morasses. More than 160 million years later, those
dinosaurs' misfortunes became paleontologists' treasures, as this unusual mode of
death and fossilization resulted in beautifully complete skeletons of scientifically
significant species. All thanks to the sauropod tracks.
But let's say your timing was even worse, and you just happened to be in the
same place where a dinosaur foot—with the rest of a living dinosaur attached to
it—happenedtoland.Ifthedinosaurwas
Microraptor
orsomeothersimilarlypuny
feathery theropod, then no big deal, unless you were a small insect. But if the foot
belongedtoatyrannosaur,ceratopsian,ankylosaur,stegosaur,orsauropod,thenthat
was a problem for any animal smaller than that foot. Sure enough, a few fossils,
suchassnailsandclams,foundindinosaurtrackswerecrushedunderfoot,although
we can't tell for sure whether they were alive or already dead when stomped.
Dinosaur tracks can also sometimes tell us if a given dinosaur had any health
problems. We know a fair number of dinosaur bones show evidence of having been
brokenandlaterhealed,butit'sdifficulttosaywhetherthesehadaneffectonanan-
imal getting around, either while healing or afterwards. Fortunately, dinosaur track-
ways are abundant enough that some with asymmetrical gait patterns pop out. In
these trackways, one side of the body stepped less distance than the other, resulting
in noticeably unequal strides. The easiest explanation for these imbalanced patterns
