The Palaeozoic Era, meaning "time of ancient life", lasted 300 million years and included many important events in evolutionary history. In the beginning of this era multicellular organisms saw an impressive increase in diversity, and most living animal phyla appeared within a few million years. Vascular plants, fish, reptiles, insects and most invertebrate groups formed during this time and life conquered the supercontinent Pangaea; which also formed during the Palaeozoic era. This era also saw the largest mass extinction in history that wiped out almost 90% of marine species. This era is broken down into six different periods, Cambrian, Ordovician, Silurian, Devonian, and Carboniferous periods.
The Cambrian Period was named after the Roman name for Wales, where rocks from this time period were first studied. During this time is when a majority of animal groups first appeared in the fossil record. The dramatic increase in biodiversity over a relatively short amount of time is often called the "Cambrian Explosion".
The fossil record from this time shows animals that have body plans similar to some living animals and represent an evolutionary lineage to most species alive today. Trilobites, an arthropod, overwhelm the Cambrian fossil record and many other incest species developed during the Cambrian Period.
Ordovician Period 505 to 440 mya
The Ordovician period is referred to as the "age of invertebrates" and gets its name from a Celtic tribe in Wales during the Roman conquest. During this time most of the area north of the topics was ocean and most of the landmass was in the southern hemisphere as the super-continent, Gondwana. Though the Ordovician period this super-continent shifted towards the South Pole and was mostly underwater. As this time period went on glaciers formed and shallow seas dried up and sea levels fell.
This period is known for the great biodiversity of marine invertebrates like trilobites and brachiopods, but also saw a community of red and green algae, primitive fish, corals, crinoids, and gastropods. Agnathans, jawless fish that had armor plates, were the first true vertebrates that appeared around 480 million years ago. Recent evidence suggests that primitive plants likely started invade land during this time.
Towards the end of the Ordovician period is marked by another mass extinction, it estimated that around 70% of marine species became extinct due to fluxuations in weather and falling sea levels.
Silurian Period 440 to 410 mya
The Silurian period saw massive changes that were important to the environment and life thus far on earth. During this time the climate stabilized at least relative to the past, sea levels rose, and life took over land.
Early vascular plants evolved on land around 425 million years ago. Coral reefs first appeared and multiplied during the Silurian period as well. Around 420 million years ago saw the first animals on land with centipedes, spiders, and mites among the earliest land variants.
The Silurian period was a very important time for fish evolution; it marked a wide and rapid spread of the jawless fishes. It also marked the first known fish with a jaw and the first freshwater fish.
Devonian Period 410 to 360 mya
During the Devonian period there were three major continental landmasses that occupied earth. Gondwanaland, which was composed of South America, Antarctica, India, Africa, and Australia dominated the southern hemisphere. North America and Europe sat together near the equator with much of the landmass under water, and to the north sat a portion of modern Siberia.
The Devonian saw a large growth of both animal and plant species on land. Two major animal species dominated the land; tetrapods, or four-legged land-living vertebrates, appeared and so did the first terrestrial arthropods, including wingless insects. One of the first amphibians lived during this time in what is now Greenland. In the oceans reef ecosystems expanded and diversified which led to the expansion and diversification of fishes to fill the newly formed niches.
By the end of the Devonian period plants with true roots and leaves evolved, many of which were quite tall. The oldest known tree, Archaeopteris, is found during this time producing the first forests on earth. Seed plants also appeared during this time, ferns and horsetails also persisted.
Carboniferous Period 360 to 286 mya
The term Carboniferous comes from England where there are rich deposits of coal; these coal deposits also occur thoughout Northern Europe, North America, and Asia. This era diveided in to two parts; Mississippian (lower Carboniferous) and the Pennsylvanian (upper Carboniferous).
During the Mississippian period much of North America was dominated by a marine environment, the major minearal from this time is Limestone, which was produced from lime-encrusted green algae and calcium carbonate.
In contrast, during the Pennsylvanian period the environment of North America was dominated by an alternating terrestrial and marine environment. The alternating ecosystems paired with the large amounts of plant material produced coal. Think about that for a second, the coal we use today to power our microwaves and heat our homes was produced almost 300 Million years ago.
During the late Carboniferous a collision of two land masses Laurussia (todays Europe and North America) and Godwanaland (todays Africa and South America) resulted in the Appalachian mountains in the Eastern U.S. and the Hercynian Mountains in the U.K.
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