Palaeozoic era [pælɪəˈzəʊɪk ˈɪərə] (jan 1, 489581342 BC – jan 1, 251581342 BC)

Description:

Great diversity of many-celled organisms in oceans. Major interval of geologic time that began 541 million years ago. The story of the earliest Paleozoic animals is one of life in the sea. Several different kinds of organisms adapted independently to life on land, primarily during the middle Paleozoic. Leafless vascular plants (psilophytes) and invertebrate animals (centipede-like arthropods) were both established on land at least by Silurian time.