Paleozoic Era

We explain what the Paleozoic era was and what this geological stage consisted of. Also, the periods that constituted it and its plants and animals.

What was the Paleozoic era?

The Paleozoic era, primary era or simply Paleozoic, was one of the eras of the geological time scale that is, the scale with which the history of the world is measured. It was the first of the three geological eras of the Phanerozoic eon that began 541 million years ago and continues today. The next two eras are the Mesozoic and the Cenozoic.

The term Paleozoic means “ancient life” (from the Greek palaio“old”, and zoe“life”), a name assigned to this period because The oldest forms of animal life proliferated and diversified there emerged at the end of the previous era, and the first beings with shells or exoskeletons appeared.

The beginning of this temporal stage, which lasted more than 290 million years, was located 541 million years ago with the dissolution of the supercontinent Pannotia, which fragmented into four continents. Its end took place 251 million years ago, with the formation of the supercontinent Pangea and the beginning of the Mesozoic.

The Paleozoic era was an extremely rich period from a biological point of view, since marked the transition from the dominance of invertebrate animals to the ones vertebrates. During this period the seas were filled with life and some organisms migrated to land. In this way, plants and animals adapted to new habitats and expanded throughout the planet.

From a climatic point of view, this period was characterized by a warm and stable climate that coincided with the proliferation of oxygen in the atmosphere. This occurred after the Late Ordovician glaciation, when a cold wave caused one of the two great mass extinctions of species of the Phanerozoic eon.

See also: Evolution of man

Stages of the Paleozoic era

The Paleozoic era is classified into six periods whose dates are estimated in millions of years (ma):

• Cambrian (541 Ma ago – 485 Ma ago). This period was characterized by the great diversification of life, known as the “Cambrian explosion”, which filled the seas with living beings and gave way, for the first time in the history of the planet, to complex multicellular beings, different from unicellular organisms. such as protists and bacteria. Around thirty-five animal phyla emerged in this period, and biomineralization (appearance of shells and shells) began. Trilobites were one of the life forms with the greatest presence in this stage.
• Ordovician (485 Ma ago – 444 Ma ago). In this period, life was contained in the seas, since the lack of atmospheric oxygen made life on land impossible. However, the diversification of living beings in the sea was exponential, and towards the end of the period the first plants and fungi emerged out of water. There was also a glaciation that affected almost all regions of the globe, which caused a mass extinction of species, known as the Ordovician-Silurian mass extinction, surpassed only by the subsequent Permian-Triassic extinction.
• Silurian (444 Ma ago – 416 Ma ago). In this period, terrestrial life continued to be vegetal and restricted to lake or swamp environments, but in the sea there was a repopulation of complex animals such as fish of different kinds, including cartilaginous fish and stickleback sharks, which dominated the warm waters throughout. along the equator. At the end of the Silurian, another mass extinction event occurred, known as the Lau event, which was due to falling sea levels but was much smaller than the Ordovician-Silurian mass extinction event.
• Devonian (416 Ma ago – 359 Ma ago). In this period bony fish appeared and large coral reefs developed. In addition, ammonites emerged and other previous but now extinct forms of life continued to exist, such as trilobites. Seed plants appeared, spreading over the land in this period and the next, and the first amphibian animals and the first terrestrial arthropods emerged. Towards the end of the period another major extinction occurred, mainly affecting marine life.
• Carboniferous (359 Ma ago – 299 Ma ago). During this period, most of the mineral coal was formed, because enormous forests were buried. Amphibians diversified, invaded land and gave rise to the first reptiles. Terrestrial insects became abundant and large, given the large presence of oxygen, which reached levels of 35% of the atmosphere. At the end of this period the supercontinent Pangea formed, and the period culminated in a new ice age.
• Permian (299 Ma ago – 251 Ma ago). This was the last period of the Paleozoic era, and witnessed the appearance of the first ancestors of mammals, turtles and dinosaurs (lepidosaurs and archosaurs). Climatically, this period tended towards aridity, so the glaciers retreated and many swamps dried up. Towards the end of the period, the Permian-Triassic mass extinction occurred, one of the largest on record, in which 90% of marine life and 70% of terrestrial life became extinct. It is not known what caused this catastrophic event from a biological point of view, but some hypotheses propose a crisis caused by high temperatures, a change in the Earth's carbon cycle, an increase in volcanic activity or the impact of a meteorite

Continue with: Geological eras

References

• Crick, R.E. & Robison, R.A. (2024). Paleozoic Era. Encyclopedia Britannica. https://www.britannica.com/
• Tarbuck, E.J. & Lutgens, F.K. (2013). Earth Sciences. An introduction to physical geology. Tenth edition. Pearson Education.
• VV.AA. (2023). Paleozoic. Vertebrates and plants. Dorling Kindersley.
• Wikipedia (sf). Paleozoic era. Wikipedia. https://es.wikipedia.org/