Earth History GEOL 2110 The Paleozoic Era Silurian and Devonian Periods - Part I 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, scorpions 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 Land Spore-bearing Vascular Plants take Root Rhynia – leaf-less tubes Psilophyton –Rooted, strong bundled stalks Lycopsids (Club Moss) Sphenopsids (Horsetail) Vascular stalks transfer water and nutrients throughout the plant

Plants colonize the land! Invasion of the Land Late Devonian – Seeded Plants and Trees Fossilized Seeds from a Seed Fern Modern-day seeded tree fern as existed in the Late Devonian Late Devonian Seed Fern Stumps, Catskill Mtns, NY Seed are better than spores at retaining moisture and are more easily fertilized

Plants colonize the land! Invasion of the Land Vascular Plants take Root

Plants colonize the land! Invasion of the Land Bugs and Slimy Creatures Follow Devonian centipede claw and head Devonian compound insect eye Millipede fossil

Plants colonize the land! Invasion of the Land Bugs and Slimy Creatures Follow

Proliferation of Reefs

Huge reefs in the Silurian and Devonian, made of: Sponges Rugose Corals Tabulate Chain Coral Heliophyllum Hexagoneria Silurian-Devonian Coral Reefs

Ecological Zonation of Coral Reefs

Reef Facies Devonian Reef Complex, W. Australia

Modern-day Reef Environment

Silurian Reef Thorton Quarry, South of Chicago

Late Devonian Extinction Another Cool Down?

Next Lecture The Paleozoic Era Silurian and Devonian Periods – Part II Stratigraphy and Tectonics