🦕Paleontology Unit 4 – Paleozoic Era

Key Concepts and Timeline

• Paleozoic Era spans from 541 to 252 million years ago (mya) and is divided into six periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian
• Cambrian Explosion (541-485 mya) marks the rapid appearance of complex animal life and most modern phyla
• Ordovician Period (485-444 mya) characterized by the diversification of marine life and the Great Ordovician Biodiversification Event
• Silurian Period (444-419 mya) known for the colonization of land by plants and the evolution of jawed fishes
• Devonian Period (419-359 mya) often called the "Age of Fishes" due to the dominance of fish and the evolution of tetrapods
• Carboniferous Period (359-299 mya) marked by the formation of vast coal forests and the diversification of insects and amphibians
  • Divided into the Mississippian (359-323 mya) and Pennsylvanian (323-299 mya) subperiods
• Permian Period (299-252 mya) characterized by the formation of the supercontinent Pangaea and ended with the largest mass extinction event in Earth's history

Geological Context

• Paleozoic Era began with the breakup of the supercontinent Pannotia and ended with the formation of Pangaea
• Cambrian Period marked by a global rise in sea levels and the formation of shallow seas that provided habitats for marine life
• Ordovician Period experienced a gradual cooling of the climate and the formation of glaciers in the southern hemisphere
• Silurian Period characterized by a relatively stable climate and the formation of extensive reef systems
• Devonian Period marked by the formation of the first forests and the deposition of red sandstones and shales
• Carboniferous Period known for the formation of extensive coal deposits due to the burial of vast swamps and forests
• Permian Period characterized by the formation of the supercontinent Pangaea and the development of an arid climate in the interior of the continent

Major Evolutionary Events

• Cambrian Explosion marks the rapid diversification of animal life, including the appearance of most modern phyla and the evolution of hard body parts
• Evolution of jawed fishes (placoderms) in the Silurian Period, which gave rise to modern fish lineages
• Colonization of land by plants in the Silurian Period, starting with small, non-vascular plants and progressing to larger, vascular plants
• Evolution of tetrapods (four-limbed vertebrates) in the Devonian Period, which gave rise to amphibians and later reptiles
• Diversification of insects in the Carboniferous Period, including the evolution of wings and the ability to fly
• Evolution of amniotes (reptiles) in the Carboniferous Period, which allowed for the colonization of drier habitats
• Appearance of the first mammals and dinosaurs in the Permian Period

Dominant Life Forms

• Cambrian Period dominated by trilobites, brachiopods, and reef-building archaeocyathids
• Ordovician Period characterized by the dominance of marine invertebrates, including graptolites, brachiopods, and cephalopods
• Silurian Period marked by the diversification of jawed fishes and the appearance of the first land plants (non-vascular)
• Devonian Period known for the dominance of fish (placoderms, sharks, and bony fish) and the appearance of the first forests
• Carboniferous Period dominated by amphibians, insects, and the first reptiles (amniotes)
  • Mississippian subperiod characterized by the dominance of crinoids and bryozoans in marine environments
  • Pennsylvanian subperiod marked by the expansion of coal forests and the diversification of insects and amphibians
• Permian Period characterized by the dominance of synapsids (mammal-like reptiles) and the appearance of the first dinosaurs and mammals

Extinction Events

• End-Ordovician Extinction (444 mya) caused by global cooling and a drop in sea levels, resulting in the loss of ~85% of marine species
• Late Devonian Extinction (375-360 mya) caused by global cooling and a drop in sea levels, resulting in the loss of ~75% of species
  • Kellwasser Event (374 mya) and Hangenberg Event (359 mya) are two distinct pulses of extinction within the Late Devonian Extinction
• End-Permian Extinction (252 mya) caused by massive volcanic eruptions in Siberia and a rapid increase in global temperatures, resulting in the loss of ~96% of marine species and ~70% of terrestrial vertebrate species
  • Also known as the "Great Dying," it is the largest known mass extinction event in Earth's history

Fossil Record and Evidence

• Burgess Shale (Cambrian) in British Columbia, Canada, provides an exceptional record of soft-bodied organisms from the Cambrian Explosion
• Mazon Creek (Carboniferous) in Illinois, USA, known for its well-preserved plant and animal fossils, including insects and amphibians
• Red Beds (Permian) in Texas and Oklahoma, USA, contain fossils of early reptiles and synapsids
• Karoo Basin (Permian-Triassic) in South Africa, provides a record of the transition from the Paleozoic to the Mesozoic Era and the End-Permian Extinction
• Rhynie Chert (Devonian) in Scotland, UK, contains exceptionally preserved plant fossils, including some of the earliest known land plants
• Solnhofen Limestone (Late Jurassic) in Germany, famous for its well-preserved fossils, including Archaeopteryx, a transitional form between dinosaurs and birds

Environmental Changes

• Cambrian Period marked by a global rise in sea levels and the formation of shallow seas, providing habitats for marine life
• Ordovician Period experienced a gradual cooling of the climate and the formation of glaciers in the southern hemisphere
• Silurian Period characterized by a relatively stable climate and the formation of extensive reef systems
• Devonian Period marked by the formation of the first forests and the deposition of red sandstones and shales, indicating a warm and humid climate
• Carboniferous Period known for the formation of extensive coal deposits due to the burial of vast swamps and forests in a warm, humid climate
  • Mississippian subperiod characterized by a warm, humid climate and the formation of extensive limestone deposits
  • Pennsylvanian subperiod marked by a shift towards a cooler, drier climate and the formation of extensive coal deposits
• Permian Period characterized by the formation of the supercontinent Pangaea and the development of an arid climate in the interior of the continent

Significance in Earth's History

• Paleozoic Era represents a crucial period in the evolution of life on Earth, spanning from the Cambrian Explosion to the End-Permian Extinction
• Cambrian Explosion marks the rapid appearance and diversification of complex animal life, setting the stage for the evolution of modern phyla
• Colonization of land by plants and animals during the Paleozoic Era paved the way for the development of terrestrial ecosystems
• Evolution of jawed fishes and tetrapods during the Paleozoic Era represents major transitions in vertebrate evolution
• Formation of vast coal deposits during the Carboniferous Period has provided a significant energy resource for human civilization
• End-Permian Extinction, the largest known mass extinction event in Earth's history, profoundly shaped the course of evolution and set the stage for the rise of the dinosaurs in the Mesozoic Era
• Paleozoic Era provides valuable insights into the long-term dynamics of Earth's climate, tectonics, and biosphere, informing our understanding of the planet's past, present, and future