Читать книгу Oceans For Dummies - Joseph Kraynak - Страница 52

The Ordovician period (from 485.4 to 443.8 million years ago) changed the face of the world. Rapid seafloor spreading resulted in high sea levels, creating new environments and habitats as well as a rapid diversification of life, including the Great Ordovician Biodiversification event. During this period:

 True fish appeared (see Chapter 12), the ostracoderms — jawless fish with bony plates.

 Ocean life also consisted of graptolites (which lived in colonies sharing the same skeleton), corals, crinoids (think starfish, sea urchins), brachiopods (clams, oysters), the surviving trilobites, gastropods (snails, slugs), cephalopods (squid, octopus), and red and green algae.

 Also swimming around during this period are six-meter-long shelled cephalopods called cameroceras (imagine a squid in a long pointy shell, three times longer than you are tall).

 The first land plants started to grow, resembling moss. These plants sucked up a lot of carbon dioxide helping to create an ice age, which is basically the opposite of what is happening now — global warming as a result of a massive release of greenhouse gasses, including carbon dioxide (thanks to human activities).

 The Ordovician-Silurian Extinction event occurred, wiping out 86 percent of marine species, including some trilobites and cephalopods. (These periods never seem to end well.)