Earth History GEOL 2110

The Paleozoic EraPart 4A: The Silurian and Devonian Periods

Time of Fish, Amphibians and Forests

Major Concepts• Biodiversity on the seafloor continued in Silurian and

Devonian times. Ammonites replaced Nautiloids; Bony fish diversified to skeletal fish.

• Land began to be populated with burrowing animals, spiders, scorpians and later amphibians

• Spore-bearing vascular plants took root in the form of club moss, ferns, horsetails and seed ferns.

• The proliferation of coral reefs caused restricted basins wherein great thickness of limestone and evaporites were deposited.

Silurian – Devonian Major Events

Marine Biodiversity Recovers from Ordovician Extinction

Spirifer Brachiopods Thick-walled, “winged” Brachs

1’Trilobites get big and defensive

Marine Biodiversity Recovers from Ordovician Extinction

Coiled Ammonoid Cephalopods

Replace Straight Nautiloids

The Age of Fishes

Jawed Spiny Acanthodians

Invasion of the LandVascular Plants take Root

Rhynia – leaf-less tubes

Psilophyton –Rooted , strong bundled stalks

Lycopsids (Club Moss)

Sphenopsids (Horsetail)

Plants colonize the land!Invasion of the LandLate Devonian – Seeded Plants and Trees

Fossilized Seeds from a Seed Fern

Modern-day spore tree fern as existed in the Late Devonian

Late Devonian Seed Fern Stumps, Catskill Mtns, NY

Plants colonize the land!Invasion of the LandVascular Plants take Root

Plants colonize the land!Invasion of the LandBugs and Slimy Creatures Follow

Devonian centipede claw and head

Devonian compound insect eye

Millipede fossil

Plants colonize the land!Invasion of the LandBugs and Slimy Creatures Follow

Proliferation of Reefs

Huge reefs in the Silurian and Devonian, made of:

Sponges

Rugose Corals

Tabulate Chain Coral

HeliophyllumHexagoneria

Silurian-Devonian Coral Reefs

Silurian-Devonian Coral Reefs

Ecological Zonation of Coral Reefs

Reef Facies

Devonian Reef Complex, W. Australia

Modern-day Reef Environment

Silurian ReefThorton Quarry, South of Chicago

Late Devonian ExtinctionAnother Cool Down?

Next Lecture

The Paleozoic EraPart 4b: Stratigraphy and Tectonics of

Silurian and Devonian Periods