The climate was one of periodic glaciations with continental glaciers moving as far from the poles as 40 degrees latitude. Few major new animals evolved, again presumably because of the short—in geologic terms—duration of the period. There was a major extinction of large mammals in Northern areas at the end of the Pleistocene Epoch. Many forms such as saber-toothed cats, mammoths, mastodons, glyptodonts, etc., became extinct worldwide. Others, including horses, camels and cheetahs became extinct in North America.
During this period mammals and birds evolved considerably.
Most notable as being the time in which mammals evolved from relatively small, simple forms into a large group of diverse animals in the wake of the extinction event that ended the preceding Period. Some of these mammals would evolve into large forms that would dominate the land, while others would become capable of living in marine, specialized terrestrial and even airborne environments. Birds also evolved considerably during this period, changing into roughly-modern forms. Most other branches of life on earth remained relatively unchanged in comparison to birds and mammals during this period.
Flowering plants proliferate, along with new types of insects. More modern teleost fish begin to appear. Many new types of dinosaurs (e.g. Tyrannosaurs and horned dinosaurs) evolve on land, as do Eusuchia (modern crocodilians); and mosasaurs and modern sharks appear in the sea. Primitive birds gradually replace pterosaurs. Atmospheric CO2 close to present-day levels.
Many types of dinosaurs, such as sauropods, carnosaurs, and stegosaurs. Mammals common but small. First birds and lizards.
Archosaurs dominant on land as dinosaurs, in the oceans as Ichthyosaurs and nothosaurs, and in the air as pterosaurs. Cynodonts become smaller and more mammal-like, while first mammals and crocodilia appear.
Landmasses unite into supercontinent Pangaea, creating the Appalachians. End of Permo-Carboniferous glaciation. Synapsid reptiles become plentiful, while parareptiles and temnospondyl amphibians remain common. In the mid-Permian, coal-age flora are replaced by cone-bearing gymnosperms (the first true seed plants) and by the first true mosses. Beetles and flies evolve. Marine life flourishes in warm shallow reefs.
Start, million years ago
Winged insects radiate suddenly; some are quite large. Amphibians common and diverse. First reptiles and coal forests. Highest-ever atmospheric oxygen levels.
Large primitive trees, first land vertebrates, and amphibious sea-scorpions live amid coal-forming coastal swamps.
First clubmosses, horsetails and ferns appear, as do the first seed-bearing plants (progymnosperms), first trees (the progymnosperm Archaeopteris), and first (wingless) insects. First amphibians still aquatic.
First Vascular plants (the rhyniophytes and their relatives), first millipedes and arthropleurids on land. First jawed fishes, as well as many armoured jawless fish, populate the seas.
Invertebrates diversify into many new types. First green plants and fungi on land. Ice age at end of period.
Major diversification of life in the XXX-ian Explosion.