These are the monsters that today's animals descended from

Source: http://www.businessinsider.com/todays-mammals-evolved-from-ancient-monsters-2017-5
June 01, 2017 at 07:03PM

After dinosaurs went extinct, things were still pretty big. During the rise of the mammals, enormous creatures roamed the Earth. These monsters would go on to become some of our smaller creatures, with one big exception.

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