The fossil case shows a living timeline from millions of years ago until the present. Throughout the ages, things have been preserved as rock, or impressions in the rock. This case shows some examples of the incredible diversity of fossils.
The Cambrian period starts 540 mya (million years ago), and shows the development of the earliest chordates (creatures with notochords or vertebrae.) It is followed by the Ordovician and Silurian periods, which show the first fish, and first land invertebrates. Next come the Mississippian and Pennsylvanian periods mark the beginning of giant insects, tree ferns, and the beginning of amphibians.
The Permian period ends the Paleozoic era with a great extinction. The Triassic, Jurassic, and Cretaceous periods make up the Mesozoic era, which shows the evolution of dinosaurs and ends with their mysterious extinction. The last era, the Cenozoic, is made of the Tertiary, or mammal period, and the Quaternary period, which shows the first humans.
Sometimes it is difficult to describe what a 600 million year old animal looks like when you only have fossil parts to work with. The museum invested in an Anomalocaris model to portray what these animals may have actually looked like. This model was modified and painted by museum volunteer Tom Johnston, and goes well with the fossilized spiked-arm fragments that Tom found in Nevada and graciously donated to the Museum. The barbed spikes of the two arms were used to pull their victim (usually a trilobite) toward their disk-like mouth that would crush the hard shell of their prey. Anomalocaris was a gigantic creature of its time and could grow to one meter (~3 feet) in length.
Good question. In order to answer this question, the Museum purchased a model of a Tully Monster (Tullimonstrum gregarium) to go with the fossilized specimen donated to the Museum by Stanley Davis. The Tully Monster was named after Francis Tully who discovered this creature in 1958. It is the State Fossil of Illinois because the fossil remains of these creatures are unique to a formation in this state. A Tully Monster is described as a strangely-designed, soft-bodied, marine, vertebrate that hunted its prey in shallow estuaries 300 million years ago. As the model demonstrates, it was a very interesting creature. New information has shown it to be a vertebrate.
In order to show the transition or link between fish and amphibians, the Museum purchased a replica of the fossil remains of Tiktaalik (tik-ta-lik). This fish lived 375 million years ago in Devonian times. Tiktaalik was a lobe-finned fish with features similar to four-legged (tetrapod) animals. Its front fins have basic wrist and finger bones that could support its weight unlike an ordinary fish fin. Thus the term “fishapod” was coined - fish with feet. Tiktaalik may have been the first fish that ventured out onto land.