Geoscience Reference
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Plant-eating dinosaurs also might have had a double threat to their dental
health posed by plants with phytoliths: silica-rich grit on their surfaces. How did
this grit get on plants? Take a close look at any vegetation alongside a stream that
experiences frequent flooding in a place with silica-rich rocks and you will likely
see clay, silt, and fine sand adhered to the leaves, branches, and stems of plants
there.Asanyfloodsubsides,suspendedsedimentcarriedbyastreamduringaflood
settles, and some of it sticks to the plants. I look for such residue whenever track-
ing animals along stream banks, and wherever noted, it informs me of former flood
heightsinthatstreamvalley.Ofcourse,windcanalsoputsomegritonplants,butit
adheresmoreeasilyifalreadywet.Nonetheless, alsothinkofhowdustcloudswere
likely kicked up by herds of dinosaurs, suspending plenty of fine-grained sediment
near the ground and likewise adding these grains to any low-lying flora.
Paleontologists who studied microwear in Edmontosaurus found out that this
dinosaur—whenitwasnotbreakingofftyrannosaurteeth—cheweditsfoodthrough
a definite series of movements, and that it was grazing. Microwear on its teeth con-
sists of four sets of scratch marks, with each set showing different orientations on
tooth surfaces. For the set with the deepest scratches that also cut across the others,
thepaleontologists defined these ashavingformedduringthe“powerstroke” phase
of chewing. This was when the hadrosaurs put the most effort into grinding down
their food, moving their jaws vertically and together.
Microwear is also visible on the teeth of other herbivorous dinosaurs, such as
ceratopsians, ankylosaurs, and sauropods. Most of these trace fossils, while telling
us how these dinosaurs chewed their food, also suggest a grazing habit, instead
of their cropping tall tree tops. For sauropods, this may seem to contradict inter-
pretations of how their long necks were used to do just that, reaching higher to
sample some tasty canopies. But anatomical studies done on some sauropods now
implythatsomeoftheselengthynecksweremaybebettersuitedforsweepinglarge
areas—back and forth—across fields of low-lying vegetation.
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