Paleozoic EraPaleozoic Era

570,000,000 years ago to 225,000,000 years ago570,000,000 years ago to 225,000,000 years ago

Life starts in the seas and moves onto land

Six periods:CambrianOrdovician

SilurianDevonian

CarboniferousPermian

Cambrian Period (570-500 MYA)

Cambrian Explosion – Most major animal phyla are found in the fossil record (mostly aquatic invertebrates with exoskeletons).

Burgess Shale – major fossil site located in Canadian Rockies

Ordovician Period (500-435 MYA)

1st vertebrates - jawless fish (filter feeders) The vertebrate protects the spinal cord,

which carries signals from the brain throughout the body.

The lamprey of today is a parasite. The hagfish is a scavenger.

Silurian Period (435-395 MYA)

1st jawed fish (later evolved into sharks-made of cartilage).

Ozone (O3) layer formed which blocks harmful UV radiation; life could evolve on land.

1st land plants (mosses & ferns) followed by 1st land animals (arthropods-spiders & scorpions).

Devonian Period (395-345 MYA)

“Age of the Fish” (giant armored fish).

1st bony fish (scales and swim bladder for buoyancy).

Devonian Period (395-345 MYA)

1st vertebrates on land – amphibians Evolved from the lobed-fin fish which include some

species of lungfish.

Carboniferous Period (345-280

MYA)

North America is at the equator (tropical swamps form coal deposits)

Amphibians & insects dominate and become large (dragon flies-1m wing span; cockroaches-10 cm long).

1st reptiles

Permian Period (280-225 MYA)

Early Permian reptiles, Cacops in front & Casea in back.

The middle Permian reptile, Anteosaurus.

Reptiles dominate. Pangaea begins to form (Appalachian Mnts; dry climate; ice age in

the southern hemisphere) Mass Extinction (90% of all species go extinct-mostly marine

invertebrates).

Mass Extinction

One of the Big FIVE Mass Extinctions