An international team of paleontologists discovered a new ancestor linked to horses and rhinoceros, by fleshing out fossils collected in India. After assembling the fossils and fleshing out the animal, the team concluded that it was a common ancestor of all perissodactyls, or odd-toed ungulates.
Researchers found the fossils during a dig through an open-pit coal mine located in the Indian state of Gujarat, which is northeast of Mumbai. Researchers found 200 bones that included parts of feet, teeth, and vertebrae. They concluded that the animal was a Cambaytherium thewissi.
After fleshing out the skeleton, the artist’s rendition revealed a tapir-like animal with the same odd toes as primitive rhinos and horses. It was classified as an early perissodoctyl, which is the same order as tapirs, horses, hippopotamus, and rhinos. Scientists always knew these animals were classified together and shared common ancestors and characteristics, but this discovery strengthens the evidence.
This small newly-discovered ancestor of horses and rhinos, is estimated to be about the size of a wild boar and weighing 45 to 75 pounds. Assembling the skeleton suggests it had five toes on each foot which would eventually become hooves. Coincidentally, primates also developed digits in sets of five at the same time.
The discovery offers new information on the life that developed during the Paleocene-Eocene thermal maximum, a time when the Earth warmed and grazing herd animals appeared alongside primates. Ken Rose, professor of functional anatomy and evolution at Johns Hopkins University School of Medicine called the creature a “cousin” of all living perissodactyls.
India broke off from Madagascar around 90 million years ago. The Cambaytherium skeleton recently assembled was estimated to have lived 54.5 million years ago, while India was an island located between Madagascar and Asia. Its herds likely started either on the African continent or in modern-day Arabia. No one knows for sure how it arrived to the island-version of India, but many theorize that there was a land bridge either from the Horn of Africa or the Arabian Peninsula.
When water levels rose and blocked access to this land bridge, the Cambaytherium was isolated and could evolve independently. That explains why it retains features not seen on either its primitive or modern day cousins. Rose describes these features as “immediate” as they show a stage of evolution in these animals, not previously documented.
Remains of Perissondactyls are discovered frequently with some bone fragments being dated as far back as 56 million years, or the beginning of the Eocene era. However, very little is known about the evolution of Perissondactyls. Between their emergence and when they became new animals, there are time periods that are not accounted for by the fossil record. While these are not the oldest fossils for this order of animal, their discovery fills in a knowledge gap regarding the background of horses and other modern Perissondactyls.
The mining company who owns these sites is very cooperative and digs continue to find more links between horses, rhinos, and this newly-discovered ancestor. Once the original site is finished, researchers will continue their efforts to the surrounding mines in hope of finding additional fossil evidence.
By Jocelyn Mackie