Historical Geology Understanding Our Planet\'s Past

Free ebooks ==> http://www.Ebook777.com THE CAMBRIAN EXPLOSION The Cambrian was an evolutionary heyday for species, featuring ...

The introduction of hard skeletal parts has been called the greatest dis- continuity in Earth history. It signaled a major evolu ...

Free ebooks ==> http://www.Ebook777.com the growth of larger animals. These, in turn, required stronger structural sup- ports ...

which were among the first organisms to grow hard shells and the dominant species for the next 100 million years. Trilobites wer ...

540 million years ago, as evidenced by the presence of Cambrian seashores in such places as the interior of North America, which ...

ilar to the spicules of some sponges today, indicating little change had taken place over the intervening period unlike in most ...

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more classes of this animal exist than of any phylum both living and extinct. The major groups of echinoderms include starfish, ...

the Cambrian explosion, when almost every major group of animals abruptly appeared in the fossil record. About 1 billion years a ...

The mollusks are a highly diverse group and left the most impressive fos- sil record of all marine animals (Fig. 51). They make ...

Free ebooks ==> http://www.Ebook777.com The crustaceans appeared at the very beginning of the Cambrian and soon became the do ...

through the Triassic periods. The conodonts are thought to be bony appendages of an unusual, soft-bodied animal resembling a hag ...

Free ebooks ==> http://www.Ebook777.com Graptolites were colonies of cupped organisms that resembled stems and leaves of plan ...

One peculiar animal aptly named Hallucigenia (Fig. 55), to honor its peculiar characteristics, was a wormlike creature that prop ...

An unusual worm had enormous eyes and prominent fins. A chunky burrowing carnivorous worm called Ottoiawas found with shelly ani ...

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example is Helicoplacus(Fig. 58), whose body parts were configured in a man- ner not found in any living organism. It was about ...

edge of Gondwana and located on the Antarctic Circle. A later collision between North America and Gondwana near the end of the C ...

T his chapter examines the early vertebrate life-forms and the geology of the Ordovician period. The Ordovician, from 500 to 435 ...

most significant advancements.The vertebrate skeleton was light, strong, and flexible, with efficient muscle attachments.The big ...