Field Museum

Observe these silurian creatures' fossils and the ways artists have imagined them. What do you notice about the animal structures pictured in these fossil images and their artist renderings? Are these fossils of complete organisms, or partial organisms? How do you think scientists and artists are able to reconstruct what an organism looked like when only partial fossil evidence is available?

Silurian Fossils and Artists Illustrations

Silurian Cephalopods possessed long, hard, segmented shells like the one shown in this fossil. They also possessed soft bodies with tentacles. These softer parts of their bodies were seldom, if not never, been preserved in fossils.

Fossil Formation

Image of a skin impression fossil from the dinosaur Edmontosaurus.

Fossil Excavation

The rock cycle illustrates the relationship between different types of rocks. Igneous or sedimentary rocks can turn into metamorphic rocks when heat and pressure are applied to these rocks. Igneous rocks are formed when melted rock cools. Sedimentary rock forms when small deposits of rock or bone are compacted into one mass, usually in underwater conditions.  

Rock Layers

In the last activity, you learned about cast, mold, trace and imprint fossils. Use this annotation activity to draw a diagram or graphic organizer explaining what you know about these different types of fossils and how they form. 

Draw Fossil Types

Learn about how paleontologists excavate, preserve, and use fossils to study Earth's past life!

All About Fossils

Cephalopods of today live only in seawater and include the squid, octopus and pearly nautilus. Cephalopod shells may be coiled, slightly curved, or straight, and all are characterized by internal chambers. The cephalopod body, which included a head with eyes, mouth and tentacles, occupied the final and largest chamber. All modern cephalopods are carnivores that capture and eat other animals. All cephalopods are swimmers, but some, such as the octopus, spend most of their time on the seafloor.

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Cephalopod - Dawsonoceras annulatum

Illustration by Tyler Ray Fewell of a Silurian Amphicyrtoceras cephalopod based on specimens from the Chicago area.

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Illustration of Silurian cephalopod

Crinoids are a type of echinoderm, a group of animals that includes starfish and sea urchins. Crinoids live only in seawater. Although uncommon today, they were very abundant in the geologic past. The crinoid skeleton is composed of hundreds of tiny plates that usually fall apart when the animal dies. 

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Crinoid - Eucalyptocrinus asper

Rugose corals are extinct, but they are related to modern corals, which live only in seawater. The animal within rugose corals resembled a modern sea anemone and captured small animals and other food particles with a ring of tentacles surrounding a mouth. Rugose corals included both solitary forms, where the coral animal was housed in a cup-shaped skeleton, and colonial forms, where many coral animals lived together in individual spaces within the skeleton

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Cnidarian - Cyathaxonia wisconsinensis

Illustration by Mary Williams of Silurian crinoid based on specimens form the Chicago area and Waldron, Indiana. 

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Illustration of Silurian crinoid

TRILOBITES are an extinct group of arthropods and possessed a head, thorax and tail. Exceptionally-preserved trilobites also show legs and antennae. Isopods, commonly known as sowbugs or pillbugs, are a modern arthropod that resembles trilobites in many ways. 

This trilobite lived during the middle of the Devonian period.  

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Trilobite - Phacopes rana milleri

Illustration by Mary Williams, based on trilobite specimens from the Chicago area

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Illustration of Silurian trilobite

Bryozoans are colonial animals that live in both freshwater and seawater. A colony is composed of hundreds of very tiny individuals, each of which has a special organ that filters small food particles from the water. Bryozoan colonies are attached to the seafloor or to other organisms.  Fan and bush-shaped colonies like this bryozoan may have functioned as bafflers.

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Bryozoan - Fenestella lonsdale

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Illustration of Silurian Bryozoan

Brachiopods are relatively rare animals today and live only in seawater. They were much more abundant in seas of the Silurian Period. Brachiopods have a shell made of two halves. Each half of the brachiopod shell has a slightly different shape. Brachiopods feed by filtering tiny food particles from seawater. 

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Brachiopod - Rhynchotreta cuneata

Art by Mary Williams, based on specimens of Stegerhyncus and other closely related species from the Chicago area and Waldron, Indiana. 

Resource Kits

Object Library

Museums

All About Fossils

Silurian Fossils and Artists Illustrations

Silurian Cephalopod Fossil