Ordovician Period


The Ordovician Period is the second period in the Paleozoic Era.
This period covers the times 488.3-443.7 million. The Ordovician period started at a major extincion event called the Cambrige Ordovician extincion event.During this period, a rich variety of marine life flourished in the vast sea, and the first primitive plants began to appear. It lasted for 44.6 million years.It ended with the Ordovician Silirian that wiped out 60% of marine genera, the second largest mass extinction of all time.
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A supercontinent named Gondwana was created when continents came together. This supercontinent then drifted south until it reached the south pole.The landmass that would become North America was combined into the supercontinent of Laurentia, which was separated from Gondwana by the narrow Iapitus Ocean. Proto-North America straddled the Equator, though to begin with it lay largely underwater.

The climate on Earth at this time was wet and warm. The sea levels were as high as 1,970 ft. above what they are today. Once Gondwana reached the South Pole, glaciers began to form over africa at the supercontinent's center. This started a 20 million year ice age that caused shallow seas to shrink away.
LIFE IN THE ORDOVICIAN PERIODAt the start, life in the ordovician was confined to the seas with new animals evolving in place of those that did not survive the Cambrian.Chief among them were the squidlike nautiloids, a type of tentacled mollusk.Another group of marine hunters were the mysterious conodonts, known mainly from the tiny fossil teeth they left behind. The few complete fossils that have been found suggest they were finned, eel-like creatures with large eyes for locating prey.
Fish started becoming more widespread in the fossil record. They were small and had downward-pointing, jawless mouths, indicating they lived by sucking and filtering food from the seabed. Bony shields covered the front of their bodies—the beginnings of a fashion for armor plating among fish. Lampreys and hagfish are these fishes' living descendants.

The hard-bodied arthropods started eyeing opportunities on land. Edging into freshwater and shallow lagoons, they likely included horseshoe crabs, which, despite their name, are more closely related to spiders and scorpions. A few species of these "living fossils" still survive today, such as along the eastern seaboard of the United States, where each spring horseshoe crabs crawl ashore to spawn.external image 220px-Orthoceras_BW.jpgexternal image Bettafish-SiameseFightingFish-Closeup.jpg http://science.nationalgeographic.com/science/prehistoric-world/ordovician.html