What is the Largest Land Mammal That Ever Lived?
The largest land mammal that is ever known to have lived was Paraceratherium, also known as Indricotherium. This animal can be described as a large hornless rhino with an elongated neck and head relative to its body. Paraceratherium had a height of 5.5 m (18 ft), over 8 m (27 ft) in length without the tail, the ability to raise its head 7.5 m (25 ft) over the ground, and a skull length of 1.35 m (4.5 ft). In comparison, the largest land mammal today, the African Bush Elephant, has a height of only 3.5 m (11.5 ft). The tallest giraffes match the height of Paraceratherium, but it weighed 5-10 times more -- estimates range from 10 to 20 tonnes.
As the largest land mammal that ever lived, Paraceratherium lacked predators, meaning the main risk to its existence would have been insufficient food rather than living threats. With a bulk that puts it into the class of some medium-sized sauropods, it would have needed to consume about half a tonne of plant matter per day to sustain itself. Analysis of its dentition shows that it grazed on the leaves and twigs of trees and large shrubs. Its skull was nearly the size of a human being. Its upper dentition only consisted of two huge incisors, so large that they look like tusks, but were concealed by the upper lip of the animal during life.
Paraceratherium lived on the Eurasian subtropical forests from the middle Oligocene to the early Miocene (about 30 to 20 million years ago). Its fossils have been found in Pakistan, Kazakhstan, India, Mongolia, and China. Though today, many of these regions are steppes, during Oligocene times they were lush subtropical forests. Though world temperatures were relatively cool in comparison to the Mesozoic, they had not yet dropped low enough to convert most of Eurasia into grasslands, as it is today.
Before Paraceratherium was discovered, the mammoth had the title of largest land mammal, particularly the steppe mammoth, which probably approached Paraceratherium in size and weight. The steppe mammoth was the world's largest land mammal at the time when it lived, 600,000-370,000 years ago.
@MrsPramm - It sounds like they thrived in sub-tropical conditions which is why food wasn't much of an object. But mammals don't reach great sizes like that in many other types of terrain. The reason we have massive whales isn't only that the water supports their weight, but also because they have huge natural food resources in krill and the animals that live off krill.
@Iluviaporos - Usually in cases where a large animal doesn't have many predators, they have a very long gestation period and don't produce many young over their lifetime. Since these were herbivores, they probably weren't actually able to run around all that much, as their bulk would have taken a lot of energy without them wasting it on activity. So their young might have been quite vulnerable to predators even if the adults weren't.
Also, it's hard for us to imagine the lifestyles of huge mammals now because there is so little wilderness left in the world. But they would have had millions of acres of food to eat and likely very little to stop them from roaming to find it. The only thing that would have kept mammals from growing even bigger would have been the effects of gravity on huge bodies and their systems, rather than because they might run out of food.
It's so unbelievable to imagine a creature that would have eaten that amount of food every day. They must have just cut swathes through the areas where they lived. I don't know how they managed to exist when there weren't any predators capable of killing them to keep their numbers down. I would have thought they'd quickly chew through all the available food and end up starving to death.
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