The following table shows the three eras and eleven geological periods that comprise the Phanerozoic. Like all geological tables this diagram has to be read from the bottom up; the lowest period in the table, the Cambrian, being the earliest.
Early Paleozoic: Age of Invertebrates Coelomate radiation Cambrian explosion - origin of major groups of organisms; nervous system, behavior patterns and simple consciousness the nascent Noosphere ; continents drift apart.
Middle Paleozoic: Age of Fish Tropical conditions. Extinction of many "experimental" animal groups; diversification of surviving invertebrate groups, rise of vertebrates fish. Life moves on land rhyniophytes , lycophytes , uniramous arthropods , and proto-amphibians. Coal forests of giant lycopsids, calamites, pteridophytes and ferns cover the tropical landmasses.
Southern landmass of Gondwanaland buried under glaciers; continents drift together. Reptiles conquer the land. The Mesozoic has been called the "age of reptiles ", but "age of dinosaurs " would be more appropriate. There is still controversy over whether dinosaurs really were stupid sluggish ectotherms "reptiles" or active high-metabolism endotherm creatures more like birds.
Even if we define them as "reptiles" the age of reptiles as such begins in the Permian period of the Paleozoic era anyway. Tropical Greenhouse Conditions. Pangaea continues during the early Triassic; then landmasses begin to drift apart.
Shallow oceans cover much of the continents, breaking the land into large islands. Many forms of life evolved and then went extinct, leaving almost everything about them a complete mystery. The oldest fossils in National Park Service areas are from the middle Proterozoic Mesoproterozoic and consist of microfossils, small macroscopic body fossils, and microbial structures from Glacier National Park , providing evidence of life from between about 1.
The stromatolites of Glacier National Park are some of the best-known examples of these fossils. It was once thought that there might be fossils in the lower Proterozoic Paleoproterozoic Sioux Quartzite at or near Pipestone National Monument , but the objects are now known to be pseudofossils, inorganic objects that have been mistaken for fossils. Every park contains some slice of geologic time.
Below, we highlight selected parks associated with the Proterozoic. This is not to say that a particular park has only rocks from the specified period. Rather, rocks in selected parks exemplify a certain event or preserve fossils or rocks from a certain geologic age.
Neogene: Cretaceous: Jurassic: Triassic: Permian: Pennsylvanian: Mississippian: Devonian: Silurian: Ordovician: Cambrian: to Explore This Park. Article Proterozoic Eon—2. Precambrian age stromatolite fossils, Glacier National Park, Montana. Visit—Proterozoic Parks Every park contains some slice of geologic time.
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