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Hoofed creatures like horses and rhinos evolved from a strange sheep-sized animal that looked like a cross between a pig and a dog, the researchers say.
Johns Hopkins University experts have uncovered the remains of the strange creature in Indian and say it dates back to about 55 million years ago.
Called Cambaytherium, it is the direct ancestor of a specific group of ungulate mammals called perissodactyls, which included rhinos and tapirs.
Also known as weird-toed ungulates, perissodactyls had five toes, weighed about four stones, and suddenly appeared 10 million years after the dinosaurs disappeared.
Lead author Professor Ken Rose said the geographic source of the precursor species of the ungulate mammals has remained a mystery until now.
The discovery is the culmination of 15 years of work by the international team of researchers and involved putting together the complete Cambaytherium skeletal anatomy from more than 350 fossils unearthed across India.
Reconstruction of the life of the Cambaytherium. Johns Hopkins University experts have discovered the remains of the strange creature in Indian and say it dates back to about 55 million years ago
The team searches for Cambaytherium fossils in the Tadkeshwar mine, Gujarat, India. These new creatures then wandered to other continents once the land link between India – once an island – and Asia was formed.
Rose said the creature’s discovery in this new study provides a window into what a common ancestor of all Perissodactyla would have been like.
He was a moderately good runner and exhibited characteristics that were a combination of perissodactyls and their more generalized mammalian predecessors.
Comparing its bones to many other living and extinct mammals, Cambaytherium was more primitive than any known perissodactyl.
Cambaytherium, first described in 2005, is the most primitive member of an extinct group that branched out shortly before the evolution of perissodactyls.
The findings confirm a theory first proposed 30 years ago that the origin of horses can be traced back to India during its northward drift from Madagascar.
The first horses were smaller than a dog and gradually dispersed to other continents, including Europe and the United States when India crashed into Asia.
Armed with the hypothesis, Rose and colleagues obtained funding from the National Geographic Society to explore India for rare rocks of the correct age that could contain fossils of perissodactyls and other groups of mammals.
The first trip to Rajasthan in 2001 had little success, providing only “a few fish bones,” Rose said. However, the latter turned out to be much more promising.
“The following year our Indian colleague, Rajendra Rana, continued to explore the lignite mines to the south and came across the Vastan mine in Gujarat,” Rose said.
“In 2004 our team was able to return to the mine, where our Belgian collaborator Thierry Smith found the first mammalian fossils, including Cambaytherium.”
He was a moderately good runner and exhibited characteristics that were a combination of perissodactyls and their more generalized mammalian predecessors
Hot, dusty work in vast open cast lignite mines in India provides evidence of the origin of perissodactyls
Comparing its bones with many other living and extinct mammals, he showed Cambaytherium was more primitive than any known perissodactyl
Encouraged, the team returned to the mines and collected fossilized bones of Cambaytherium and many other vertebrates, despite the harsh conditions.
Rose said, “The heat, constant noise, and coal dust in the lignite mines were harsh, basically trying to work hundreds of feet below near the bottom of the open cast lignite mines that are actively mined around the clock. 24, 7 days a week “.
Through the accumulation of many years of demanding field work, the team now believes they have finally solved the mystery of mammals.
Despite the abundance of perissodactyls in the Northern Hemisphere, Cambaytherium suggests the group probably evolved in isolation – in India.
The first horses were smaller than a dog and gradually dispersed to other continents, including Europe and the United States when India crashed into Asia. The researchers collected bones from over 350 fossils to create a complete skeleton
Called Cambaytherium, it is the direct ancestor of a specific group of ungulate mammals called perissodactyls, which also include rhinos and tapirs
Cambaytherium, first described in 2005, is the most primitive member of an extinct group that branched out shortly before the evolution of perissodactyls
This happened during the Paleocene from 66 to 56 million years ago, just after the dinosaurs were wiped out by an asteroid attack.
These new creatures then wandered to other continents once the land link between India – once an island – and Asia was formed.
Rose added: “At the time of Cambaytherium, we think India was an island, but it also had primates and a rodent similar to those that lived in Europe at the time.
One possible explanation is that India passed close to the Arabian Peninsula or the Horn of Africa and that there was a land bridge that allowed animals to migrate.
“But Cambaytherium thewissi is unique and suggests that India has been truly isolated for a while.”
The findings were published in the Journal of Vertebrate Paleontology.
HOW THE HORSE LOST ITS FINGERS
The evolution of horses has involved adaptation to changing environments, predation and human domestication.
The ancestors of modern horses had a small body, short legs, three toes on the front legs and four toes on the hind legs.
It is believed that a more exposed environment may have forced the horse to develop longer legs to escape predators and that they increased in size to be more difficult to eat.
The loss of toes may have allowed the horses to carry more weight and move faster on their longer legs.
A single hoof better supports a horse’s weight and allows it to swing its legs more efficiently to gallop at a much greater speed.
This is one of the crucial adaptations to allow horses to move as quickly as they do today.
Horses are the only creature in the animal kingdom to have only one toe: the hoof, which first evolved about five million years ago.
Their toes first shrunk in size, apparently, before disappearing entirely.
The ancient horse moved relatively slowly with a small body, short legs, three toes on the front feet and four toes on the hind legs. The artist’s 1905 impression of an ancient horse was made by Charles Knight
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