Ordovician Fossils

Paleobiology
 

Fossils of the Ordovician

505 to 440 million years ago

Related:
Paleozoic Paleobiology



Ordovician Life and Fossils

Ordovician LifeMetazoan invertebrates dominated Ordovician life. While far less famous than the Cambrian Explosion, the Ordovician encompassed a massive adaptive radiation where marine faunal genera increased some four fold. Carbonate shell-secreting organisms were particularly successful, and competed with trilobites in continental shelf communities. These included appearances and radiations of corals, articulate brachiopods, bivalves, cystoids, gastropods, nautiloid cephalopods, bryozoa and crinoids. The competition and the spread of fiercer and larger predators provided selective pressures on trilobites, resulting in exotic forms from a trilobite evolutionary arms race. Reef building came to be dominated by corals. Graptolites thrived and Green algae from which plants probably evolved became common. The first terrestrial plants resembling liverworts appeared; spores from land plants have been identified in uppermost Ordovician sediments. The first jawed fish appeared late in the Ordovician. Mass marine life extinctions that occurred during in the late Ordovician (443.7 ± 1.5 million years ago) claimed some 60% of genera, thereby creating niches for benthic (bottom-dwelling) and planktonic (floating, swimming) organisms. The fossils below are a representative sampling from the Ordovician fossil record.

Caleidocrinus multiramus Crinoid
Zahohany, Czech Republic
Stromatolites
Oneota Formation, Glover's Bluff, Wisconsin
Isotelus gigas
Trilobite Order Asaphida
Lindsay Formation, Ontario, Canada