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
Trilobites
get big and
defensive
Spirifer Brachiopods
Thick-walled, “winged” Brachs
1’
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
Lycopsids (Club Moss)
Rhynia – leaf-less tubes
Sphenopsids (Horsetail)
Vascular stalks transfer water and
nutrients throughout the plant
Psilophyton –Rooted , strong bundled stalks
Plants colonize the land!
Invasion of the Land
Late Devonian – Seeded Plants and Trees
Late Devonian Seed Fern
Stumps, Catskill Mtns, NY
Seed are better than spores at retaining
moisture and are more easily fertilized
Modern-day seeded tree fern as
existed in the Late Devonian
Fossilized Seeds from a Seed Fern
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:
Silurian-Devonian
Coral Reefs
Tabulate
Chain
Coral
Sponges
Rugose Corals
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