Geological Time periods
Palaeozoic
Precambrian (4500 to 541 million years ago)
- Major events: largest geological time period, spanning from the formation of the earth to
the establishment of microbial and multicellular life. Formation of the atmosphere, snowball
earth and great oxidation event.
- Fossil sites: Ediacaran hills (Australia)
- Example species: Stromatolites, Kimberella, Dickinsonia, Spriggina, Mawsonites
Cambrian (541 to 485.4 million years ago)
- Major events: Cambrian explosion, evolution of hard-bodied animals, first vertebrates.
- Fossil sites: Burgess shale (Canada), Chengjiang (China)
- Example species: Anomalocaris, Haikouichthys, Hallucigenia, Wiwaxia, Opabinia
Ordovician (485.4 to 443.8 million years ago)
- Major events: cambrian-ordovician extinction, major diversity in marine life, non-vascular
plants include mosses, red and green algae, major glaciation triggering an extinction event.
- Fossil sites: Canning Basin (Australia), Lake Winnipeg (Canada)
- Example species: Cameroceras, Conodont, Megalograptus, Crinoids
Silurian (443.8 to 419.2 million years ago)
- Major events: began with extinction triggered by ordovician glaciation, first vascular land
plants, rising sea levels resulting in new aquatic ecosystems.
- Fossil sites: Appalachian Mountains, great lakes (USA)
- Example species: Cooksonia, Cephalaspis, Brontoscorpio, Pterygotus, Megamastax
, Devonian (419.2 to 358.9 million years ago)
- Major events: ‘age of fish’ – diversification of bony fish, separation of land mass into
Euramerica and Gondwana, earth's first forests consisting of horsetails and ferns, tetrapods
first appear.
- Fossil sites: red hill (Pennsylvania), Ohio state park (Indiana), Devonian fossil gorge (Iowa)
- Example species: Dunkleosteus, Bothriolepis, Hyneria, Archaeopteris, Hynerpeton,
Gondwanascorpio
Carboniferous (358.9 to 298.9 million years ago)
- Major events: swamp forests covering much of the earth's surface, arthropod gigantism due
to much elevated oxygen levels, minor extinction at the end of the period known as the
carboniferous rainforest collapse.
- Fossil sites – Joggin (Nova Scotia), East Kirkton quarry (Scotland), Mazon Creek (Illinois)
- Example species: Arthropleura, Meganeura, Stethacanthus, Lepidodendron, Petrolacosaurus,
Pulmunoscorpius, Cacops
Permian (298.9 to 251.9 million years ago)
- Major events: diversification of reptiles, appearance of ‘mammal-like reptiles ‘ (synapsids),
appearance of the first modern trees, end of the period saw the largest extinction event in
the history of life, wiping out ~95% of species, likely caused by a warming climate and
associated oceanic changes.
- Fossil sites – Ural Mountains (Russia), Texas red beds (USA)
- Example species: Dimetrodon, Seymouria, Edaphosaurus, Diplocaulus, Inostrancevia,
Glossopteris, Coelurosauravis
Palaeozoic
Precambrian (4500 to 541 million years ago)
- Major events: largest geological time period, spanning from the formation of the earth to
the establishment of microbial and multicellular life. Formation of the atmosphere, snowball
earth and great oxidation event.
- Fossil sites: Ediacaran hills (Australia)
- Example species: Stromatolites, Kimberella, Dickinsonia, Spriggina, Mawsonites
Cambrian (541 to 485.4 million years ago)
- Major events: Cambrian explosion, evolution of hard-bodied animals, first vertebrates.
- Fossil sites: Burgess shale (Canada), Chengjiang (China)
- Example species: Anomalocaris, Haikouichthys, Hallucigenia, Wiwaxia, Opabinia
Ordovician (485.4 to 443.8 million years ago)
- Major events: cambrian-ordovician extinction, major diversity in marine life, non-vascular
plants include mosses, red and green algae, major glaciation triggering an extinction event.
- Fossil sites: Canning Basin (Australia), Lake Winnipeg (Canada)
- Example species: Cameroceras, Conodont, Megalograptus, Crinoids
Silurian (443.8 to 419.2 million years ago)
- Major events: began with extinction triggered by ordovician glaciation, first vascular land
plants, rising sea levels resulting in new aquatic ecosystems.
- Fossil sites: Appalachian Mountains, great lakes (USA)
- Example species: Cooksonia, Cephalaspis, Brontoscorpio, Pterygotus, Megamastax
, Devonian (419.2 to 358.9 million years ago)
- Major events: ‘age of fish’ – diversification of bony fish, separation of land mass into
Euramerica and Gondwana, earth's first forests consisting of horsetails and ferns, tetrapods
first appear.
- Fossil sites: red hill (Pennsylvania), Ohio state park (Indiana), Devonian fossil gorge (Iowa)
- Example species: Dunkleosteus, Bothriolepis, Hyneria, Archaeopteris, Hynerpeton,
Gondwanascorpio
Carboniferous (358.9 to 298.9 million years ago)
- Major events: swamp forests covering much of the earth's surface, arthropod gigantism due
to much elevated oxygen levels, minor extinction at the end of the period known as the
carboniferous rainforest collapse.
- Fossil sites – Joggin (Nova Scotia), East Kirkton quarry (Scotland), Mazon Creek (Illinois)
- Example species: Arthropleura, Meganeura, Stethacanthus, Lepidodendron, Petrolacosaurus,
Pulmunoscorpius, Cacops
Permian (298.9 to 251.9 million years ago)
- Major events: diversification of reptiles, appearance of ‘mammal-like reptiles ‘ (synapsids),
appearance of the first modern trees, end of the period saw the largest extinction event in
the history of life, wiping out ~95% of species, likely caused by a warming climate and
associated oceanic changes.
- Fossil sites – Ural Mountains (Russia), Texas red beds (USA)
- Example species: Dimetrodon, Seymouria, Edaphosaurus, Diplocaulus, Inostrancevia,
Glossopteris, Coelurosauravis
