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The Paleocene
The Paleocene is the first epoch of the Cenozoic. It started approximately
65 million years before the present and lasted approximately 10 million years.
During this epoch, ancient species of primates and primate-like relatives first
evolved. The end of the Mesozoic (the previous era) marked the conclusion of
the Age of Reptiles and the start of the Age of Mammals. The explosion of mammalian
life during this epoch brought about more than 22 new orders and is considered
to be one of the most amazing examples of evolutionary diversification.
Earth looked much different in the Paleocene. India and Africa were islands,
and North America was connected to Europe, which was more like an archipelago
of islands than the continental body it is today. South America and Australia
were connected to Antarctica, forming one giant landmass known as Gondwana.
Although temperatures fluctuated throughout the epoch, they were generally cooler
than at the end of the Mesozoic and in the Eocene. It is believed that this
cooling was due in part to dust and debris that was thrown into the atmosphere
by the meteorite collision. Nevertheless, Earth's climate during the Paleocene
was significantly warmer than it is today, and subtropical conditions existed
around the world.
Primate ancestors that lived during the Cretaceous were small omnivores (they
ate both plant and animal material), and they were adaptable enough to survive
the mass extinction and live on into the Paleocene. These ancestors gave rise
to the earliest primates and some of the relatives of primates, such as tree
shrews, flying lemurs, and bats, whose first representatives also occur in the
fossil record at this time. Plesiadapiformes, an order of mammals that appear
to be very primate-like, flourished in the Paleocene. It's long been thought
that plesiadapiformes were archaic primates ancestral to all modern primates.
Their ancestral status has been challenged, which makes unraveling the origin
of primates difficult and speculative. As more fossil material is found from
this epoch, researchers hoped to gain a better picture of how the biological
Order Primates, to which we belong, first evolved.
In addition to primates, species in many other new orders were evolving. The
first carnivores evolved in the Paleocene, though the order Carnivora did not
thrive until the Oligocene. The forests supported a great variety of insects,
resulting in a great deal of insectivores from this time period. Browsing animals
(leaf-eaters) were also prevalent in the Paleocene, many of which have descendants
that can be found in modern tropical and subtropical environments. In the late Paleocene temperatures started to rise, which caused change in
the vegetation. The forests that had housed numerous primate relatives were
replaced with denser, often tropical, forests. Species either adapted to the
new climate and environments or died out. The pleisiadapiform species that thrived
during most of the epoch dwindled and left only a handful of species in the
Eocene. It is in the Eocene that we see the first modern-looking
primates.
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