Indricotherium
Order: Perissodactyla
Family: Hyracodontidae
The Indricotherium, also know as Baluchitherium and Paracaratherium,
was a gigantic long-necked, hornless rhinoceros that lived in Asia during
the Oligocene and early Miocene eras (from about 37 million to 25 million
years ago). This extinct ungulate (hoofed mammal) had three toes on each
foot like modern rhinoceroses. Living in the open woodlands of what is
now Pakistan and China, they are believed to have evolved from the most
primitive of hyracodonts and would have looked more like a cross between
an elephant and a horse. Its ancestors were more likely similar to tapirs
than to mo dern rhinos.
Although estimates of its overall dimensions vary, most paleontologists
agree that the Indricotherium was the largest land mammal, known from the
fossil record, to have ever walked the earth. Its skull alone measures an
incredible 4 feet in length. Overall weight estimates range from 15 to 33
tons. Standing 18 feet at the shoulder, it would have been four to five
times larger than modern elephants. A restoration in the American Museum
of Natural History, New York City, measures 17 feet 9 inches to the top
of the shoulder hump and 37 feet in total length.
Careful analysis indicates that the Indricotherium may not have
exceeded 44,000 pounds. This theory is based on the idea of "metabolic
cost" to demonstrate how gravity imposes an upper limit to the size
of mammals. Although not proved, this estimate would indicate that the Indricotherium's
weight may have been pushing the maximum amount allowed by nature.
Discovered in Urga, Mongolia, in August 1922, the Indricotherium
was the first great triumph of the Roy Chapman Andrews expedition to Mongolia.
Ironically it was discovered by accident lying exposed at the bottom of
a gully as the expedition stopped to investigate before heading back to
camp. The discovery was made at the last moment by one of the expedition's
drivers named Wang. Portions of the skeleton were immediately excavated,
including a 100-pound rock containing the skull.
Indricotherium probably lived in small family-grouped herds. These
herds would have roamed through an open woodland environment, picking and
browsing the tops of trees for food. Their immense size would have made
them virtually inaccessible to predators. Hyaenodon and Dinictis were two
predators of the time that may have posed a threat to the herd's young.
But, except for newborn calves, they were probably altogether avoided by
most predators.
The Indricotherium's tall legs and long neck would have made it
perfectly suited for browsing the otherwise untouched green leaves and twigs
at the tops of trees. They would have filled a niche in the ecosystem similar
to that of today's giraffes. Much like today's rhinoceroses and tapirs,
the Indricotherium probably had a prehensile upper lip. Along with this
and its four tusk-like teeth, two on bottom and two on top, the Indricotherium's
mouth would have been perfectly adapted to stripping leaves from their branches.
The eventual extinction of the Indricotherium was brought about
by the changing habitat in which it lived. During the early Miocene, the
native forest of ancient China and Pakistan disappeared and gave way to
open grasslands. With its main food source gone, the Indricotherium would
have been too large to survive on open plains. |