Indricotherium – Animal of the Week

For my first extinct animal of the week, it seems only appropriate to make it a grand one. Instead of choosing something you’ve all heard of before, I’ll try something a little more obscure.

This will also be my last animal of the week. Seeing as I’m about to start grad school, I just don’t have the time to continue publishing these on a regular basis. After a while, I will take the existing animal of the week posts and move them into the category nature. In its place, I’ll post about the natural world as I’m inspired by my studies.

What’s the largest animal ever? Most of you probably know it’s the Blue Whale.

And the largest land animal in history? Many of you would know that it’s one of those big dinosaurs like Brontosaurus. (Officially the title goes to the sauropod Argentinosaurus.)

But can you name the largest land mammal ever to roam the earth? This week’s animal is Indricotherium transouralicum. Like many of the coolest animals from long ago, it lacks a common English name.

There may not be a lot known about Indricotherium, at least there’s less on the web about it than other animals.

The name Indricotherium comes from the russian word indrik. In Russian mythology, the indrik was the most powerful of animals — the lord of all animals — believed to rule the seas and shake the earth when he came down from his holy mountain.

Size and Weight

This giant mammal is related to our modern day rhinoceroses. Like modern day rhinoceroses, it had three toes. However, it lacked the familiar horn of its modern day relatives. Its fossils are known only from central asia during the Oligocene and early Miocine, 20 to 30 million years ago. They were certainly enormous. At the shoulder, Indricotherium stood 18 feet tall! A human would barely reach the knee of these creatures. They were 30 feet long, and their skulls alone were about 6.5 feet in length! Initially, their weight was believed to be up to 30 tons but, as more complete fossils began to surface, scientists realized that this was probably exaggerated. From what I can tell, there isn’t universal consensus on its weight. Current estimates for Indricotherium put its weight between 15 and 20 tons. It’s important to keep in mind that an animal’s weight is dependant upon its soft tissue, something that is not preserved in fossils. Therefore, it’s difficult to determine weights of animals known only from the fossil record.

Ecology

Judging from its teeth, Indricotherium was a herbivore and is believed to have stripped the vegetation off trees with its high reach. Like modern day rhinoceroses and tapirs (another living group of odd-toed hooved mammals), Indricotherium probably had a prehensile upper lip, to aid in grasping its food. In this way, they would have filled the niche of a giraffe in their environment. If Indricotherium is like its living relatives today, they may have traveled about in small groups as they searched for food. Their size would have taken all but their young off the menu from known predators.

Evolution and Taxonomy

Indricotherium has a somewhat unclear taxonomy. Whenever it is decided that two species are not actually different but the same, by the rules of taxonomy, the name that has been described to science first is considered to have priority over any newer names. For a long time, Indricotherium was better known as Baluchitherium until it was decided that specimans of that species were in fact the same species. Another genus of very large extinct rhinoceroses is Paraceratherium. Though members of this genus are considered to be distinct at the species level, there is disagreement on whether they are the same genus as Indricotherium. If this is the case, Paraceratherium was described to science first, and thus that name would have priority. Hence the genus name of Indricotherium would be changed to Paraceratherium. I certainly have not researched these animals enough to form any kind of an opinion, and I wait to see if paleontologists can come to consensus.

Indricotherium is placed in the Order Perissodactyla — the odd-toed ungulates — and the family Hyracodontidae, a sister family to Rhinocerotidae (the family that rhinoceroses belong to).

Rhinoceros first show up in the fossil record in the Eocene as rather small animals, and by the Miocene, they have diversified into many species with a wide geographical distribution. They went extinct in North America by the Pliocene and later disappeared from Europe and northern Asia during the Pleistocene. (Need help with the different time eras? Here’s a good reference.) Today only 5 species of rhinoceros remain with us, limited to Africa and southeast Asia. Most are critically endangered due to poaching and habitat loss.

Sources

• Wikipedia – general information on Indricotherium
• Wikipedia – general information on rhinoceroses
• The Mammal Society – This British organization had a page on Indricotherium