A NEW CHALLENGE
rise of the mammals
Following the K/T extinction that marked the end of the Mesozoic era, a new era saw the light: the Cenozoic era. For the first 10 million years of that era, the world was recovering with a warm climate and tropical forests covering the planet. With most land plants and large vertebrates gone, plenty of ecological niches were ready to be filled and the survivors were more than happy to do that.
The surviving avian dinosaurs continued to evolve and diversify more into the birds we’re familiar with nowadays.
Meanwhile, plenty of herbivore mammals similar to horses and deer were thriving on the forest floor due to the lack of predators, however, insectivore mammals that survived the extinction were beginning to develop a taste for bigger prey and carnivorous mammals began to appear, adapt and take their place in ecological niches.
Alongside these groups, other mammals were living in the trees with features believed to be very similar to the features of primates.
At the time, the world was warmer than today’s world, and the species were adapted to that environment. However, the world was struck with even warmer temperatures: it was a period known as “Thermal Maximum”
ancestors of horses, rhinos and tapirs. And it’s in the late Eocene, that the clade of the monkeys, the
Simians, began to appear. with the Eocene epoch ending and the Oligocene epoch starting, we started to see the ancestors of the
“Old World Monkeys” and
the apes but it was also
an epoch that was marked
by the formation of the ice
sheets in Antarctica and a low
-temperature Europe that marked an extinction event for the “older” mammals and a migration for the “newer” mammal species with carnivores and herbivores alike moving in to a new European environment: Grasslands. Grasslands marked also a selection issue as grass was more difficult to digest giving an ultimatum for herbivores: digest or die, so those who were able to digest grass correctly, like the ancestors of today’s cows and sheep, were able to adapt creating a shift among the herbivores. Meanwhile, the Simians were also shifting apart as in South America the New World Monkeys were appearing with a diet based on fruits and a small size similar to the traits of older simian ancestors while Old World Monkeys in Asia and Africa had a wider diet and had to spend more time on the ground rather than in the trees.
caused by possible volcanic eruptions and greenhouse gases released from the ocean floor, but one thing is for sure: animals like reptiles who were adapted to hot temperature thrived and this is the era when large reptiles like the biggest snake ever, Titanoboa, and the carnivorous massive turtle Carbonemys lived. During that time, other mammals were also
appearing and adapting
and some of the
true primate ancestors were appearing. But, another era started with the temperatures going from greenhouse temperatures to ice age temperatures caused by massive amounts of ferns growing and taking massive amounts of the world’s carbon dioxide from the atmosphere causing the world to cool down.
During the early Eocene, a lot of mammal groups from the early Cenozoic, the Paleocene, couldn’t adapt to cooler temperatures and
Cenozoic, the Paleocene, couldn’t adapt to cooler temperatures and went extinct while other mammals
on some continents died out. But that’s when the true ancestors of today’s mammals began to appear
in records like rodents and the
Purgatorius unio
This small mammal is a late Mesozoic survivor of the mass extinction. Nocturnal and is believed to have been an ancestor to all primates.
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