During the Pliocene, most landmasses arrived in their present-day positions. The world was also getting a lot colder. Not only had Antarctica grown bigger yet, but an ice cap dominated the northern Arctic, too. This also meant even more invasion of grass.
New and diverse ruminant animals appeared during this epoch. Some animals that were following the forest-to-grass trend were the newly evolved hippopotamuses, gazelles, antelopes, and giraffes that still had short necks.
A major advancement of the mammalian carnivores in this epoch was the "idea" of hunting in packs. This provided many benefits. An obvious advantage is that a very large prey could be killed, even if it was twice the size of any individual pack member.
Also, a hierarchy could be organized in each of the social packs. This gave better communication, so the prey could be more easily killed.
Plant life's pattern remained the same as every epoch's throughout the Tertiary. The cooler the climate, the more grass there was. And the Pliocene was certainly cool.
Cenozoic Era: Tertiary Period: Pliocene Epoch