Paleozoic era: the Second era of the World
Paleozoic era: Its several periods
The time period between the Precambrian and Mesozoic periods lasted for nearly 340 million years. This era is divided into several periods. The Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian. The Cambrian period is described as the first part of this era. It started approximately 590 million years ago when the continents formed one large super continent called the Gondwana. This super continent included all of today's continents such as Africa, Antarctica, South America, Western Australia along with some parts of India, Mexico, Florida, southern Europe and China. These massive continents were situated in the southern hemisphere and stretched almost to the South Pole and towards the North Pole.
Paleozoic era: Climate
Initially the climate was pretty cool to moderate which later warmed up with the onset of the global warming which scientific studies of the red sandstones and saline deposits revealed. The development of the flora and fauna started extensively during the Cambrian period. The sea started to be the birth ground of organisms like fungi, trilobites, and crayfish like creatures that had a hard chitin amour along with prehistoric mussels. The algae, seaweed, and terrestrial creatures mainly survived the flora world and plants did not show up at that time.
The Ordovician period followed the Cambrian period which existed from 505 and 439 million years ago. The geological situation did not change much from the Cambrian era except for the fact that the continents did start to shift towards the coast and the continents became more flooded. The era witnessed an ice age, which is evident from the moraines deposited by the glaciers. This period saw the evolvement of invertebrate creatures in the sea within the warm climate regions.
The deposit of the dark slates showed the existence of the multicolor graptolites which is an extinct form of flagella form which had a chitin skeleton. Numerous types of calcera evolved in the shallow seas during this time as well. Even the existence of the first fish was also eminent during this period. these fish did not have fins or jaws. There was no trace of plants or trees in this era but the green and the blue algae was flourishing from the seawater to the fresh water. The plants did not seem to have come into existence before the Silurian period.
The third phase of the Paleozoic era was the Silurian period that encompasses a period between 438 and 408 million years ago. The geographically two continents were found totally interlocked, the northern Laurasia and the southern part called the Gondwana. Alternatively both sections were submerged underwater. The North Pole was somewhere near the northern Pacific Ocean and the South Pole somewhere near southwestern Africa. The equator passed over the southeastern Europe over the northern Australia and Greenland to the center of America.
During this time the climate was warm and humid. Near the end of this era it did turn very dry. The most common marine animals that did exist during this period were the invertebrates such as trilobite, graptolites and simple corals. While the fauna consisted of the algae that stalked themselves at the bottom of the seabed, they also had tentacles around their bodies. The corals built great cliffs but became extinct nearly 230 million years ago. Marine scorpions grew into gigantic forms during this time.
The first jawless fish that had a cartilaginous skeleton appeared in the sea during this time, two of these species, which is the eel, like fresh water lamprey and slimy worm like blennies survive even today. During the end of this period we can find the existence of the primeval ferns and club mosses on the land.
The fourth period of the era was the Devonian period that existence between 490 and 360 million years ago. During this time the continents were constantly on the move where the North Pole turned to be warmer while the South Pole witnesses severe ice belt.
Numerous animal species started to evolve during this period. The shield headed fish was the first vertebrate creature that was present during this period. The original skeleton was formed not by the bones but by the cartilaginous matter. During this period there was thorny and lobe finned fished that had rigid skeletons and thick fins and was able to survive on the land. They were able to exist in dried ponds and water bodies and later evolved into land creatures.
The Maine life included creatures like the corals, ammonites, sanails, crayfish and echiderms while the scorpion, arachnids, terrain reptiles and wingless insects lived on land.
The forest contained club mosses that grew nearly 30 meters, fern and horsetails that are very much similar to today's swampy forests. The first vertebrate evolved during this time and evidence of amphibians were not too rare at this time as well. At the end of the carboniferous period the animals started developing lungs for breathings. These reptiles with lungs did not require to return to water for laying eggs. They were the predecessors of today's tortoises and turtles.
The next period was the Carboniferous period which is the fifth and last phase of the Paleozoic era that began 360million years ago and ended 286million years ago. This period is also known as the anthracite because the largest coal deposited on the earth was said to have been formed during this time due to the favorable climatic and geological factors that existed on the earth during that time.
The climate was hot and humid which is similar to the climate prevailing in the rainforests today. This period saw the evolvement of the mountains and plates due to the havoc tectonic movements and the land was majorly covered with dense forest that often remained submerged under the water over some period of time.