Dates	Period		Physical/Biological Features
280,000,000 – 225,000,000	PERMIAN		Final folding of Appalachians and central European ranges; great glaciers in Southern Hemisphere and reefs in warm northern seas; trees of coal forests declined; ferns abundant; conifers present; first cycads and ammonities appeared; trilobites became extinct; reptiles surpassed amphibians.
320,000,000 – 280,000,000	PENNSYLVANIAN	CARBONIFEROUS	Mountains grew along east coast of North America and in central Europe; great coal swamp forests flourished in Northern Hemisphere; seed-bearing ferns abundant; cockroaches and first reptiles appeared.
345,000,000 – 320,000,000	MISSISSIPPIAN		Land plants became diversified, including many ancient kinds of trees; crinoids achieved greatest development; sharks of relatively modern types appeared; little evidence of land animals.
395,000,000 – 345,000,000	DEVONIAN		Mountains raised in New England; land plants evolved rapidly, large trees appeared; brachiopods reached maximum development; many kinds of primitive fishes; first sharks, insects, and amphibians appeared.
435,000,000 – 395,000,000	SILURIAN		Great mountains formed in northwestern Europe; first small land plants appeared; corals built reefs in far northern seas; shelled cephalopods abundant; trilobites began decline; first jawed fish appeared.
500,000,000 – 435,000,000	ORDOVICIAN		Mountains elevated in New England; volcanoes along Atlantic Coast; much limestone deposited in shallow seas; great expansion among marine invertebrate animals, all major groups present; first primitive jawless fish appeared.
570,000,000 – 500,000,000	CAMBRIAN		Shallow seas covered parts of continents; first abundant record of marine life, especially trilobites and brachiopods; other fossils rare.