Geoscience Reference
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ating them became greater, though, she stopped. Going any farther would expend
more resources than it was worth, so she would just have to wait for another oppor-
tunity.
She went back to the fresh, bite-sized
amuse-bouche
of hadrosaur remaining
on the ground at the site of her attack, sniffed it, picked it up with her mouth,
chewed,andswallowed.Thenextday,itsremnantswouldcomeouttheotherendof
her digestive tract with most of its useful nutrients absorbed, but with bits of etched
vertebral bone and a few of the hadrosaur's muscle fibers preserved in the feces.
She walked down into the lower part of the floodplain and moved along the trend
oftherivervalley.Herhuge,thicklypadded,three-toedandclawedfootprintsoblit-
erated some of those left only fifteen minutes before by the terrified “
Mononykus”
and
Thescelosaurus
.
Unknown to this
Tyrannosaurus
and every other dinosaur in the area that day,
the river valley itself was also a remnant of a former dinosaur presence. Herds of
immense long-necked sauropod dinosaurs had moved through this place several
tens of million years before, but were now mostly gone from this part of the world.
Trails made by these sauropods, caused by habitual movements over hundreds of
generations, had breached levees and cut across river channels. These alterations
provided new avenues for flooding water that eventually changed local drainage
patterns, which in turn impacted regional flow.
The sauropods had grazed and trampled the local vegetation sufficiently that
plant roots no longer bound sediments near the river channels. As a result, every
flood rapidly eroded banks, broadened channels, and spread sand and mud farther
out onto floodplains than before. A combination of flooding and windblown sand
from this widened river built up levees, which provided banks suitable for hosting
the burrowing ornithopods. Over time, this synergism between sauropods—and
later, large ornithopods and ceratopsians—with sediments, and moving water irre-
vocably changed the neighboring habitats and became the “new normal” for all di-
nosaurs that lived and evolved there afterwards.
