Findings: Remembering Indricothere

Sixty-five million years ago, an asteroid slammed into the Yucatan Peninsula, decimating the planet and wiping out all of the dinosaurs of the Cretaceous period. But that is not the end of story. There were survivors of this catastrophe, and over tens of millions of years, they went to form one of the most impressive and spectacular displays of wildlife the Earth has ever known.

Fast-forward 10 million years: The dinosaurs are gone. In their wake, a new order of creatures is growing, multiplying, and adapting into every niche of the ecosystem. At this stage — 25 million years before the appearance of man — Earth is in full blossom, providing a fresh and rejuvenated habitat for a gallimaufry of creatures you have never heard of. These animals are big, loud, and unlike anything you have ever seen.

Tyrannosaurus rex is a distant memory in this world. Here, mammals and birds of whopping and unfathomable sizes rule the land. Gastornis, a flightless, flesh-eating bird the size of a grown man, tears its prey to shreds with one thrash of its colossal beak.

Basilosaurus, an ocean-dwelling lizard half the size of a Boeing 737, waits for a shark and then swallows it whole. Andrewsarchus, the largest mammalian carnivore in the world, is six feet tall and has a head the size of an alligator.

The six-part BBC television documentary Walking with Beasts (aired in North America on the Discovery Channel under the title Walking with Prehistoric Beasts) does an exemplary job bringing to life Gastornis, Basilosaurus, Andrewsarchus, and other relics of this prehistoric era.

Like the dinosaurs before them, the distribution of prehistoric beasts was widespread. But for mammalian giants, Central Asia was a particular hotbed.

Mongolia: The time is the Oligocene, a period in Earth’s history from 33.9 million to 23 million BCE. The Oligocene comes at the heels of a trying period in Earth’s history, when the ecosystem is erratic and climate change is tumultuous. During this time, one in every five species went extinct. But the Oligocene marks the beginning of a vigorous resurgence.

Now, the Earth is fresh, florid, and ready to house the next generation of inhabitants. Some of the beasts of the Oligocene have grown to enormous sizes — sizes that greatly exceed those of modern-day animals.

The Chalicothere, a bizarre-looking creature with the gate of a horse and the face of a sloth, was nine feet tall, and walked on its knuckles. Entelodonts, ferocious hunters and ancestors of today’s pig, were seven feet tall, and as bulky as the Rhinoceros. But nowhere is this abundance of giants more apparent than in Mongolia.

It is nightfall in the Mongolian desert, and there is a disturbance in the leaves. The rustling grows louder until, slowly, the outline of an animal the size of three double-decker buses emerges from the foliage. It is an Indricothere, the largest land mammal that ever lived, and it is hungry.

Out of all the bizarre animals that emerged after the decimation of the dinosaurs, none left a footprint as large and unforgettable as the Indricothere.

Woolly mammoths and saber-toothed tigers are arguably the most tossed-about relics from the age of prehistoric beasts. But the Indricothere dwarfed a woolly mammoth by several magnitudes.

Measuring 40 feet tall and weighing 12 tons, a full-grown Indricothere could have competed in size with any dinosaur of its day.

These precursors to the modern-day rhinoceros were so enormous that they were able to lead a life free of predation simply by intimidating any animal that crossed their path. Even Entelodonts were no match for the Indricothere, whose rawhide skin and thunderous stomp were enough to send the hungriest carnivores scampering for the hills.

Despite their tremendous size, molar remnants of the Indricothere suggest that it was an herbivore. Like many large herbivores today, the Indricotheres roamed the Oligocene landscape in packs.

Indricotheres were found as far west as Eastern Europe, but are most widely discovered in the middle of Central Asia.

Mike Fortelius is a professor of ecological paleontology at the University of Helsinki and an expert on the Indricothere. He provides insightful audio commentary on the Discovery Channel’s website that expounds on these facts.

Fortelius points out that large animals are better able to cope with bad spells (such as long dry seasons) and other hardships. These conditions are often encountered in the middle of a large continent. The rise of the Indricothere is concurrent with the mounting dry spells that ravaged Asia during this period in geological history.

The Indricothere is a member of order Perissodactyla — hoofed animals with an odd number of toes. A modern example of an odd-toed ungulate is the Brazilian tapir. Visually, llamas (South American pack animals) provide a good representation of a grossly downscaled Indricothere — minus the fur. Still, like many relics of this forgotten world, Indricotherium transouralicum lacks a common name.

There is a skeleton of Indricotherium transouralicum in the National Science Museum in Tokyo. In Reutlingen, Germany, a short-lived exhibit on dinosaurs included a massive monument to the Indricothere.

However, the best way to get your hands on Indricothere is to view BBC’s Walking with Prehistoric Beasts. (This DVD is available at the Carnegie Museum of Natural History.)

The dinosaurs lived, and the dinosaurs died. For many, the story ends there. But for 25 million years, another group of animals came to dominate the Earth.

These were not the dinosaurs, but were ferocious and unwieldy mammals. Mammals that would eventually evolve into some of the most highly developed organisms on Earth. In an era of mammals that culminates with modern man, the Indricothere was our finest hour.