Out of the three geological eras, the Paleozoic Era is the earliest of all. Divided into six distinct geological periods, the Paleozoic Era is the longest Era from the Phanerozoic Eon, which lasted from 541 million years ago to 252 million years ago, existing over roughly 290 million years. In this article, we’ll tell you everything you want to know about Paleozoic Era, such as Paleozoic Era facts, timeline, climate, animals, plants and more. So keep reading!
Paleozoic Era Definition:
Followed by the Neoproterozoic Era and succeeded by the Mesozoic Era, the Paleozoic Era saw substantial changes in geology, climate, and evolution of life. The first geological period in the Paleozoic Era – Cambrian – saw the greatest change in life form ever recorded in history, which is often referred to as the “Cambrian explosion”. Most of the life forms that exist today, including Arthropods, Mollusks, Fishes, Amphibians, amongst others started their evolution in the Paleozoic Era. So, without any further ado, let’s discover the specifics of the Paleozoic Era!
Fun fact: Did you know where was Africa located during the Paleozoic Era? It was at the south pole! It was a part of the supercontinent Gondwana. 200 million years ago when the supercontinent broke, Africa moved to its place on the current map.
Paleozoic Era Facts
The Paleozoic Era is full of interesting events and things, most of which even baffles scientists and historians. Let’s get into the meat and get an overview of the Paleozoic Era:
- The Paleozoic Era spanned a stunning 290 million years of time, making it the longest era ever.
- Before the Paleozoic Era, the earth did not have enough oxygen to sustain life.
- Paleozoic Era was the first time when planet earth saw life in more than one cell – formation of multicellular organisms.
- Paleozoic Era had trees without any roots, leaf, or flowers.
- Paleozoic Era saw two extinction events, one in the middle and one which ended it.
- Paleozoic Era ended with the largest of the five mass extinctions of species, with 96% marine life and 70% terrestrial land life erased from the face of the planet.
- The middle of the Paleozoic Era faced the Ordovician-Silurian extinction event which wiped out 60% marine life.
- Paleozoic Era had a supercontinent called Gondwana which was nearly all the land mass on the planet.
Paleozoic Era Timeline
The Paleozoic Era started off approximately 541 million years ago, and ended about 252 million years ago. Hence, having a time span of 290 million years, making it the largest of the three eras in the Phanerozoic Eon.
The Paleozoic Era started just after the end of Proterozoic Eon, in which time period earths’ atmosphere became abundant in oxygen. It is clear then, that in the Paleozoic Era, life forms started evolving for the first time, as oxygen did not exist as abundantly before the Proterozoic Eon.
The Paleozoic Era is divided in six distinct geological time periods, namely: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian.
Cambrian Geological Period
The Cambrian geological time period is known for marking a profound change in life on Earth. Before the Cambrian period, a majority of the life forms were small and unicellular. This changed when the 55.6 million years long Cambrian period give rise to more complex species, formation of multiple biological kingdoms, and relatively intelligent animals.
Ordovician Geological Period
The Ordovician Period lasted for around 41.2 million years. Like the Cambrian Geological Period, it too flourished in sustaining life. Invertebrates, mostly mollusks and arthropods, were dominating the oceans. The world’s first vertebrates – the fishes – also evolved in Ordovician Period, which slowly went on to overthrowing the domination of invertebrates in the water. However, unlike the Cambrian period, Ordovician Geological Period saw its end by various extinction events, known as Ordovician-Silurian extinction events.
Silurian Geological Period
Starting rough – wiping out roughly 60% of earths’ marine life forms in the Ordovician-Silurian extinction events – the Silurian Geological Period that lasted for 25 million years is best known for its diversification of jawed fish and bony fish. This marked significant evolutionary changes, as it gave the base to vertebrates and flagged the start of truly complex life forms in terms of structure and intelligence.
Devonian Geological Period
The Devonian Geological Period, which spans over 60 million years, is marked by the first significant adaptive radiation of life on dry land. Adaptive radiation is a process whereby species evolve and diversify from a common ancestral species. Forests also started rapidly occupying dry land in the Devonian Geological Period. This is the time period wherein earth actually started becoming “green” in color, as Devonian period saw rapid proliferation of plants throughout landmass.
Carboniferous Geological Period
Spanning 60 million years, the Carboniferous Geological Period has its name from coal, where – derived from Latin – Carboniferous means coal-bearing. Many coal beds were formed globally during the Carboniferous Geological Period, which we take advantage of today. Terrestrial life on land was well established during the Carboniferous Period. Amphibians were prominent vertebrates on land.
Fun Fact: The oxygen content on planet earth reached its highest level ever, with air having approximately 35% oxygen content. Today, approximately oxygen content is only 20%.
Permian Geological Period
The last of the six geological periods in the Paleozoic Era, the Permian Geologic Period spans 47 million years, succeeded by the Triassic Geological Period which belongs to the Mesozoic Era. It is named after the Russian city, Perm.
The Permian Geological Period ended – along with the Paleozoic Era – by a mass extinction event that erased 96% of marine species and 70% of terrestrial land species. This is known as the Permian-Triassic extinction event and it took 30 million years for natural life to recover from this disastrous extinction.
Paleozoic Era Climate
The Ordovician and Silurian Geological Periods were relatively warm periods that saw an abundance of greenhouse gases. They also had the highest sea levels of the Paleozoic era, with more than 200m of the sea level today! A 30 million year cool period broke up this heated environment, known as the Early Paleozoic Icehouse. It resulted by the culmination in the Hirnantian glaciation, 445 million years ago at the end of the Ordovician geological period.
Moreover, the climate in the early Paleozoic Era was strongly zonal, which led to climate becoming warmer, but the living space of most organisms of the time, mainly inclusive of marine life, became steadily colder.
In the mid-Paleozoic Era, the climate was considerably stable as compared to the early Paleozoic Era. Sea levels had dropped due to the ice age, but slowly recovered over in the Silurian Geological Period and Devonian Geological Period. Shallow and warm seafloor was also created due to the northward movement of Gondwana (a supercontinent that existing during the Paleozoic Era) in the mid-Paleozoic Era. As plants took hold on the continental margins, oxygen levels increased and carbon dioxide dropped steadily, thus resulting in increase of oxygen content in atmosphere.
The climate in the late Paleozoic Era is largely unknown and in fact a matter of debate amongst historians and biologists. Most of them claim that there was one or maybe two ice ages during the late Paleozoic Era – especially in the Carboniferous Era – due to the extreme spike of oxygen and reducing of carbon dioxide, which almost nullified heat trapping mechanism of earth. Although with the passing of time, both oxygen and carbon dioxide recovered to normal levels, the formation of Pangea – the singular massive motherland which then broke off into the 7 continents – led to climate extremes, which is often associated with falling sea levels and increased carbon dioxide content.
Paleozoic Era Fossils
Paleozoic Era is one of the most interesting matters of study for historians, especially since there are so many available fossils formed throughout the 290 million years of the Paleozoic Era. The fossils show proof of land dominance by smaller and less complex organisms such as early and primitive arthropods which looked like centipedes with a larger head and tail. So many fossils of arthropods have been found that a few scientists actually believe that arthropods ruled the world, though this is generally put down by most biologists and historians in saying that land and terrestrial life was extremely limited, and most evolution look place solely in marine life.
Moreover, fossils of marine life are also found in abundance. Fossils which look extremely similar to modern-day fishes have been found, with similar bone placement, fin placement, and exterior structure. However, many fossils have been found which appear to be the primitive versions of fishes, with the relatively thinner and broader body, no and small fins, and few bones.
But perhaps the most interesting fossils that have been found are those of amphibians or similar looking organisms. Scientists broadly believe that amphibians are relatively complex animals in terms of structure and intelligence, and thus should not have evolved so early as it Paleozoic Era. However, fossils clearly showing the structure similar to amphibians, including 4 feet with fingers, face, body constantly lined with bones, and tail, have been found. This also means that amphibians have survived all five major life extinctions on planet earth.
Paleozoic Era Animals
During the Paleozoic Era, there were multi-cell living beings like trilobites, mollusks, jawless fish, ocean growth lastly, jawed fish, sharks, plants and early creatures of land and water and reptiles. In the beginning, there was an expansion in the varied variety of multi-celled creatures, while towards the end of the Paleozoic Era, the biggest mass extinction reached the finishing point of the 290 million years and started off the Mesozoic Era.
In the Cambrian Geological Period, scavenger trilobites were prominent. Archaeocyathids were sponge-like and lived in reefs. Mollusks, snails and primitive algae also existed. The oldest known creature with a vertebra was the jawless fish.
In the Ordovician Geological Period, there were bottom-dwelling marine organisms like brachiopods. Further extending in the Devonian Geological Period, sharks and other bony fish started evolving. The main vascular plants had no roots, leaves, or flowers. Hence, it wasn’t exactly a very “green” earth back then. The first few land creatures were spineless in structure, for example, scorpions, millipedes, and insects. Cockroaches also evolved during the Paleozoic Era.
Fun Fact: Amphibian species evolved from lobe-finned fish, a type of fish which has its fins shaped like lobes.
Graptolithina in Paleozoic Era
Now that we have discussed about fossils and animals in Paleozoic Era, let’s combine the two a bit and discuss about Graptolithina, also known as Graptolites. Graptolites are the invertebrate organisms which existed during the Paleozoic Era, especially during the Cambrian Geological Period. They are believed to be colonial marine organisms which were prominent underwater during the Paleozoic Era. They are an extinct species, and we have nothing more than their fossils from which we analyze their existence and evolution.
Graptolites were floating organisms frequently found as carbonaceous impressions on black shales, but their fossils have been found in an uncompressed state in limestone as well. They had a fingernail-like outer covering and lacked hard body parts, which makes scientists predict that they were spongy animals. However, when found as impressions, the specimens are flattened, and much detail is lost due to which no solid conclusion has been made of them till date. The graptolite animal was symmetrical and tentacled. Scientists predict that graptolites are related to the hemichordates, an early group of invertebrates which were primitive and simple in structure and intelligence.
Well, the Paleozoic Era was certainly an interesting 290-million-year long era with interesting life forms and ridiculously varying climate – from extreme heat to a full-fledged ice age! From Africa being on the south pole to massive extinction of 96% of marine species, the Paleozoic Era remains a topic of interest for all us nerds.
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