The Paleocene Epoch.
This time period occurred directly after the end-Cretaceous mass extinction event, and was the beginning of the so-called “Age of Mammals”. The supercontinent Gondwana, formed by Australia, Africa, South America and Antarctica was starting to split apart. South America was an island continent, and Europe and Asia were connected to North America, leaving land bridges that enabled early mammals to spread throughout the world.

The global temperature was warmer than it is today, though the 9.5 million year duration of this epoch was much drier than those before and after. Because of these higher temperatures, thick forests grew across the continents, and modern plants, like cacti and palm trees, began to develop.

Because 80% of all life on earth had been destroyed, the mammals and birds remaining found it easy to flourish, evolving relatively quickly to adopt the niches that had been left vacant by the dinosaurs. As a result, a lot of species grew to huge sizes. Birds such as Gastornis evolved as a remarkable shadow of its ancestors, a post-Cretaceous theropod, becoming giant, flightless and predatory. It would have fed upon mammals such as the condylarths.

Flying Monsters- with David Attenborough

Summary of Prehistory

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scientificillustration:

n102_w1150 by BioDivLibrary on Flickr.

Propalaeohoplophorus a Glyptodont or Giant Armadillo

Reports of the Princeton University Expeditions to Patagonia, 1896-1899..
Princeton,The University,1901-32 [v. 1, 1903].
biodiversitylibrary.org/page/35832471

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Homo ergaster

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Homo rudolfensis