PERMIAN PERIOD
The Permian witnessed the diversification of the early
amniotes into the ancestral groups of the mammals, turtles, lepidosaurs and archosaurs.
The world at the time was dominated by a single supercontinent known as
Pangaea, surrounded by a global ocean called Panthalassa. The extensive
rainforests of the Carboniferous had disappeared, leaving behind vast regions
of arid desert within the continental interior. Reptiles, who could better cope
with these drier conditions, rose to dominance in lieu of their amphibian
ancestors. The Permian Period (along with the Paleozoic Era) ended with the
largest mass extinction in Earth's history, in which nearly 90% of marine
species and 70% of terrestrial species died out. It would take well into the
Triassic for life to recover from this catastrophe.
Terrestrial life in the Permian included diverse plants,
fungi, arthropods, and various types of tetrapods. The period saw a massive
desert covering the interior of the Pangaea. The warm zone spread in the
northern hemisphere, where extensive dry desert appeared. The rocks formed at
that time were stained red by iron oxides, the result of intense heating by the
sun of a surface devoid of vegetation cover. A number of older types of plants
and animals died out or became marginal elements.
The Permian began with the Carboniferous flora still
flourishing. About the middle of the Permian a major transition in vegetation
began. The swamp-loving lycopod trees of the Carboniferous, such as
Lepidodendron and Sigillaria, were progressively replaced in the continental
interior by the more advanced seed ferns and early conifers. At the close of
the Permian, lycopod and equicete swamps reminiscent of Carboniferous flora
were relegated to a series of equatorial islands in the Paleotethys Sea that
later would become South China.
The Permian saw the radiation of many important conifer
groups, including the ancestors of many present-day families. Rich forests were
present in many areas, with a diverse mix of plant groups. The southern
continent saw extensive seed fern forests of the Glossopteris flora. Oxygen
levels were probably high there. The ginkgo’s and cycads also appeared during
this period.
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