To discuss what creatures were present millions of years ago in what
is now Illinois, we must first talk about what this area and the rest
of the earth was like in that time.
First, the climate during this time was much warmer than it is today.
Most of the area that is Illinois today was actually part of a swampy
tropical forest.
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Courtesy of US Geological Survey
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North America did not look like it does today. A vast gulf of water
separated most of eastern North America from the western mountains.
North and South America were also separated by water.
Because of the warmer temperatures and ocean currents at that time,
ice caps at the poles were not present.
This time period is thought to be near the end of the dinosaurs. Were
dinosaurs in Illinois? Scientists think there might have been, but no
fossil remains have been found. Part of the reason is that the rocks
that would contain these fossils have been eroded away in most parts
of the state. However, there is some research that is currently being
done in southern Illinois in an area that still has some of these rock
layers left.
What kind of animals might have been around 65 million years ago?
Small mammals may have been present. These animals were probably active
at night, so they could avoid predators.
Dinosaurs that may have been in the eastern part of North America were
different than those in western North America. Main types of dinosaurs
in the east were smaller in size than those present in the West. A family
of dinosaurs found in the east was the Ornithomimus.
Larger dinosaurs could be found in the western land areas, such as
the Tyrannosaurus.
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