Complex sentence: A platybelodon is a large herbivorous mammal, related to the elephant (order Proboscidea), lived during the Miocene epoch, about 15 million years ago.
Split into simpler sentences: A platybelodon is a large, extinct herbivorous mammal related to the elephant (order Proboscidea). They lived during the Miocene Epoch, about 15 million years ago.