The Paleozoic era is a stage in the history of the earth that spanned more than 290 million years, beginning more than 540 million years ago and ending more than 250 years ago. The period begins after the disintegration of the supercontinent Pannotia, and ends with the formation of the supercontinent Panguea.
Regarding the life transformations On earth, it can be said that at the beginning of the Paleozoic there was no living being that was not aquatic, while when the period ended many animals had already conquered the mainland. During the first part of the period the more complicated forms of life evolved, while towards the end the lungs that gave rise to amphibians developed.
The transformations were geological and also related to life on the planet, and they were so great that the period has been divided into substage, which are detailed below.
- Cambrian (570 to 505 million years). The world looked like a vast blue ocean with some white clouds, where the continents were four and small. An ice age that began in the Precambrian had ended. The following species developed there:
- Chordates
- Animals with hard structures, such as brachiopods.
- Trilobites.
- Thousands of strange tiny animals, soft-bodied or hard-shelled.
- Some types of mollusks.
- Halkieriea, known as the oldest vertebrates.
- Ordovician (505 to 438 million years). The seas gradually receded, leaving areas uncovered. The continents, then, were approaching each other, and the Iapetus Ocean closed, while the Panthalasa covered most of the Northern Hemisphere. The climate was uniform and warm all over the planet. There were some animal species.
- Brachiopods.
- Mollusks.
- Gastropods.
- Bryozoans.
- Anutiloids.
- Cephalopods.
- Massive extinctions, product of the glaciations.
- Silurian (437 to 408 million years). The earth undergoes some folds, where the strata move or are inverted. A large number of land areas rise, and in that period another ice age occurs, affecting what is now North Africa. Some animals are recognized.
- Fish with backbones.
- Fish with jaws to eat, and scales to protect themselves.
- Eurypterid arthropods.
- Devonian (407 to 362 million years). Europe definitely collides with North America, forming the continent of Laurasia. This shock produces red, sandstone-like sediments. The land did not undergo major geotectonic changes, but a North Atlantic continent and another of Gondwana were defined, separated by the Tethys Sea. Some species originated.
- Gigantrostráceos.
- Lobed-finned fish.
- Tiktaalik.
- Ichthyostega, and some other tiny land animals.
- Carboniferous (361-290 million years): Two of the continents come together, creating the conditions for the emergence of forests that will become coal basins in Europe and North America. Alaska collides with America, and the origin of some mountain ranges (such as the Appalachian Mountains) is produced by the folds of the earth’s crust. Large areas of forests are formed, and the atmosphere ends up changing, forming the ozone layer. The following animals saw the light there:
- Myriapods.
- Arachnids, sometimes giant.
- Amphibian, large and multiple shapes.
- Permian (289 to 246 million years). They came to join the three existing continents, forming a supercontinent known as the Pangea. In the same way, a universal ocean known as Wegener’s Panthalase was formed. In any case, the Sea of Thetis split the only continent in half, which is why its conception of the Mediterranean comes from there. The formation of mountain ranges in America, Europe and Asia was completed, and the central part of the Andean mountain range emerged. The climate varied according to the hemisphere, being warmer in the south. The following species already lived.
- Adaptation of reptiles to dry and desert areas.
- Reptiles with dorsal crest.
- Cynodonts, which will become mammals.
- Pelycosaurs.
- Archeosaurs.