The Ordovician Period

The Ordovician period was a time when different parts of the Earth changed and new life forms were discovered. This period occurred after the Cambrian period during what is called the Paleozoic era (540 to 248 mya). Some types of animals discovered during this period are said to be the first findings known to later transform during future time periods. Different varieties of plants were also discovered, mostly found growing in the water. First, many things contributed to the environment the Ordovician Period had. “Areas north of the tropics was almost entirely ocean; most of the world’s land was assembled into the southern supercontinent Gondwana. Gondwana shifted towards the South Pole and much of it was inundated underwater throughout the

Some of the different varieties of life forms were found in trilobites and conodonts. “Most fossils were found in shale, limestone, dolostone, and sandstone. In the tropical Ordovician environments, blastoids, bryozoans, corals, crinoids appeared. Many kinds of brachiopods, snails, clams, and cephalopods also appeared for the first time in the geologic record. Ostraderm remains from Ordovician rocks comprised some of the oldest vertebrate fossils. The ostraderm was discovered to be a jawless, armored fish.” (UCMP) “Trilobites did not die out when the mass extinction occurred at the end of the Cambrian period. These beings lived on and many more new species developed. Cephalopods became the dominant predators during the Ordovician period. Cephalopods are a group of mollusks that are related to the octopus and squid. An example of a straight-shelled cephalopod is the orthoceras; this creature lived in the largest open end of its shell. The orthoceras could rise and fall in the ocean water like a submarine. The tube in the center of the animal was called the siphuncle. When the siphuncle was filled with air, its body floated upward. A burst of air out the back of the siphuncle would push the animal forward.” (fossils-facts-and-finds.com) “The number of families of known marine invertebrates increased from around 200 at the end of the Cambrian period to around 500 in the early Ordovician. The warm and widespread shallow continental seas were the perfect environment for numerous groups of organisms. Micro-organisms such as colonial blue-green algae stromatolites were widespread. Foraminifera, were marine amoebas that built tiny shells. These animals were appearing for the first time. Another creature that also appears is the stromatoporoids, guessed to be a sponge-like organism. An increase in the amount of micro-plankton caused an increase in the number and diversity of filter feeders. The lophophorates