Arthropods

= Arthropods are the most successful group of animal phyla. Out of the more than a million animal species, at least 900,000 of them are arthropods. Arthropods are classified by their unique jointed appendages and hard exoskeletons. Arthropods first came to Earth in the Pre-Cambrian Period. [Normally, there would be a period behind it, but the Cambrian is dated the farthest back of all periods. The time before this period was known simply as the Pre-Cambrian] The first arthropods actually turned out to be the most interesting. These animals were known as trilobites. Trilobites were actually the first animal to have eyes. That changed very soon however, for when the Pre-Cambrian Period ended, the Cambrian explosion began. The Cambrian Explosion was when thousands of new species evolved in less than a million years. [Mostly all of these new animals had eyes like trilobites] The Cambrian and Ordovician Periods were dominated by all sorts of sea life. However, the arthropods were overshadowed by the new armored fishes in the Silurian and Devonian Periods. During the Carboniferous Period, arthropods flourished in all the seas. But no period was like the Permian. During the Permian Period, arthropods literally owned the seas. Thier population almost doubled and it looked like life was just getting perfect. But the Permian extinction brought complete doom upon all arthropods, espicially the trilobites. The arthropod population began to get very scarce. The trilobites became totally extinct. =