Figure 23. The drawing shows what crinoids in the ancient Kansas sea looked like. The crinoid fossil was found in limestone, millions of years after the animal died and was fossilized.
We would never have known which animals had lived in Kansas if there were no fossils. Fossils are the remains of plants or animals that have been preserved in rock. Body parts, especially bones and teeth, may be preserved. Impressions or outlines of plants and animals are also found in some rocks. Sometimes the only evidence of an early animal is a footprint or track that has become hardened in rock. All of these--bones, teeth, impressions, outlines, footprints, and tracks--are fossils.
Fossils help geologists learn about the Earth. Another scientist, the paleontologist, specializes in studying fossils and life in the past. Both geologists and paleontologists explore the Earth's surface and subsurface to learn more about its history.
Through fossil finds, paleontologists can piece together evidence of earlier life and landscapes. On one expedition in 1885, a footprint was found in a subsurface sandstone dug from a well in Ellsworth County. The sandstone was formed from sand deposited during the Cretaceous Period. Because of the position of the toes, scientists decided the impression was probably made by a bird.
Not far from where the footprint was found, impressions of leaves were found in the same layer of sandstone. The leaves came from trees similar to modern-day oaks, willows, poplars, laurels, sarsaparillas, magnolias, and sassafras trees. None of these trees is native to Ellsworth County today, although people have planted some of them in the area. They grow naturally in other areas of the world where the temperatures are warmer. In the same sandstone surrounding the area where the leaves were found, fossils of marine fish and seashells were found.
Figure 24. A fossil leaf found in Dakota Sandstone, which was deposited about 100 million years ago in Ellsworth County.
By putting all of these fossil finds together, we know that a sea covered Ellsworth County millions of years ago. In this sea was at least one small island that was covered with beautiful trees and inhabited by birds. Insects also lived on the island because the leaves showed signs of insect attacks. The types of trees that were able to grow indicate the climate was probably warmer and wetter than it is today.