List of the Paleozoic life of Illinois

This list of the Paleozoic life of Illinois contains the various prehistoric life-forms whose fossilized remains have been reported from within the US state of Illinois and are between 538.8 and 252.17 million years of age.

†Hyolithes

Fossilized fronds of the Carboniferous-Early Cretaceous seed fern Alethopteris
Life restoration of the Carboniferous amphibian Amphibamus
Fossil of the Carboniferous horsetail relative Annularia
Fossils of the Carboniferous-Permian bryozoan Archimedes
Illustration of a fossil of the Carboniferous-Permian spider Arthrolycosa . Charles Emerson Beecher (1889).
Fossilized shell of the Late Ordovician-Carboniferous brachiopod Atrypa
Fossilized shell of the Silurian-Early Triassic mollusc Bellerophon
Life restoration of the Carboniferous amphibian Brachydectes
Fossil of the Early Ordovician-Silurian trilobite Bumastus
Fossilized stems from the Carboniferous-Permian horsetail relative Calamites
Fossilized fronds of the Carboniferous seed fern Callipteridium
Life restoration of the Carboniferous Chimaera relative Caseodus
Fossil of the Middle-Late Ordovician trilobite Ceraurus
Fossilized shell of the Middle Devonian-Permian brachiopod Cleiothyridina
Life restoration (foreground) of the Permian-Jurassic lobe-finned fish Coelacanthus
Fossilized foliage of the Carboniferous-Permian conifer relative Cordaites
Fossilized skeleton of the Carboniferous-Permian reptile relative Cricotus
Fossil of the Carboniferous shark Ctenacanthus
Restoration of the Cambrian-Middle Devonian nautiloid cephalopod Cyrtoceras
Elasmobranch † Dabasacanthus inskasi Zangerl 1979 from Mazon Creek
Fossil of the Late Ordovician-Middle Devonian trilobite Dalmanites
Fossilized axial skeleton of the Carboniferous-Permian amphibian Diplocaulus
Life restoration of the Late Devonian-Carboniferous Chimaera relative Edestus
Fossilized skeleton of the Carboniferous-Permian bony fish Elonichthys
Fossilized calyx of the Silurian-Middle Devonian crinoid ("sea lily") Eucalyptocrinites
Fossilized shell of the Silurian-Permian sea snail Euomphalus
Illustration of fossil of the Carboniferous millipede Euphoberia
Fossil of the Late Ordovician-Permian tabulate coral Favosites
Fossilized tooth of the Carboniferous shark Glikmanius
Life restoration of the Carboniferous four-limbed animal precursor Greererpeton
Fossil of the Ordovician bryozoan ("moss animal") Hallopora
Fossilized shells of the Cambrian-Permian brachiopod relative Hyolitha
Life restoration of the Permian amphibian Isodectes
Fossilized shells of the Middle Ordovician-Permian nautiloid cephalopod Kionoceras
Illustration of a fossil of the Carboniferous centipede Latzelia
Restoration of the Carboniferous-Late Triassic club moss relative Lepidodendron . Eli Heimans (1911).
Shell of the Cambrian-modern brachiopod Lingula
Shell of a Lithophaga , or date mussel
Life restoration of the Permian snake-like amphibian Lysorophus showing speculative egg-coiling behavior
Fossilized shell of the Carboniferous-Permian nautiloid cephalopod Metacoceras
Fossils of the Early Devonian graptolite Monograptus
Fossilized shell of the Early Devonian – Triassic sea snail Naticopsis
Fossilized frond of the Carboniferous seed fern Neuropteris
Interior of a fossilized shell of the Early Ordovician-modern marine bivalve Nucula
Fossils of the Late Devonian-Permian fern-like fronds Pecopteris
Fossil of the Silurian-Carboniferous crinoid ("sea lily") Periechocrinus
Fossil of the Late Ordovician-Late Devonian trilobite Phacops
Life restoration of the Carboniferous-Permian amphibian Phlegethontia .
Life restoration of the Carboniferous-Permian bony fish Platysomus
Life restoration of the Carboniferous Chimaera relative Polysentor
Restoration of the Silurian trilobite Proetus
Life restoration of the Carboniferous insects Protophasma and Titanophasma
Fossilized skeleton of the Carboniferous snake-like amphibian Pseudophlegethontia
Fossilized shell of the Silurian-Eocene articulate brachiopod Rhynchonella
Fossilized stump of the Carboniferous-Permian club moss relative Sigillaria
Modern specimen of the marine bivalve Solemya
Fossilized leaves and branches of the Devonian-Triassic horsetail relative Sphenophyllum
Srokalarva berthei part and counterpart
Life restorations of a male (foreground) and female (background) of the Late Devonian-Carboniferous Chimaera relative Stethacanthus
Fossil of the Carboniferous Chimaera relative Symmorium
Fossilized shell of the Early Ordovician-Late Devonian probable mollusc Tentaculites
Restoration of the mysterious Carboniferous life-form Tullimonstrum , or the Tully monster
Illustration of a fossil of the Carboniferous millipede Xyloiulus