Geologic TimeScale 1

Precambrian

Informal name for the eventful 4 billion years that preceded the Cambrian period

• Edicarian organisms left no know modern descendants + hard to tell their shape

• Happened first

Cambrian period

543-490 Mya

• Paleozoic period

• Fossils of all major phyla of animals appeared within a few million years in the Cambrian seas

• Algae, sponges, jellyfishes, worms, nautiloids, trilobites

• The Burgess Shale - mudslide that preserved organisms from the period

• Happened 2nd

Ordovician period

490-443 Mya

• Paleozoic period

• First vertebraes

• Jawless fish, corals, clams, sponges, algae present

• Ended with a mass extinction killing many marine invertebrates

  • Gondwana headed for the South Pole

• Happened 3rd

Silurian period

443-417 Mya

• Paleozoic period

• First plants with specialized water and mineral conducting tissues; the vascular plants evolved during this period along with terrestrial animals

• Also fungi and jawed fish

• Happened 4th

Devonian period

417 to 354 mya

• Paleozoic period

• “Age of fishes”

  • Fishes with bones or cartilage skeletons

• Toward the end, the first amphibians appeared

• Mass extinction of marine life marks the end of this period; life on land was majorly spared

• Scorpions and millipedes lived on Earth

• Ferns, horsetails, seed plants

• Lobe-finned fish

• Happened 5th

Carboniferous period

354 to 290 mya

• Paleozoic period

• “Age of amphibians”

• Eventually gave rise to reptiles

• Foraminiferans, bryozoans, ferns, insects were abundant and flourishing

• “Carboniferous” means coal bearing; plants died at the end of this period, creating coal

• Happened 6th

Permian period

290 to 248 mya

• Paleozoic era

• Seed plants called gymnosperms and reptiles became more prevalent

• Reptiles introduced new adaptation - the amniotic egg (embryo can develop on completely dry land)

• Ended with a mass extinction that wiped out more than 90% of species in shallow areas of the sea; possibly due to drop in sea level, CO2 of organic molecules accumulation in the atmosphere, depleting O2 supplies in the ocean

• Happened 7th

Ostracoderms

Jawless fish

Placoderms

Jawed fish that became extinct at the end of the Devonian period