Some 55 million years ago, the Indian subcontinent was still a floating island, making its way to a dramatic tectonic collision with Asia. About the time, scientists say, an animal dubbed Cambaytherium thewissi emerged. According to a new study, Cambaytherium is an ancient cousin of horses, rhinos and tapirs -- a group (or order) of modern animals known as Perissodactyla, or odd-toed ungulates.
Researchers have been able to trace the ancestors of modern horses, rhinos and tapirs as far back as the beginnings of the Eocene epoch, about 56 million years ago, but the story of the evolution of early odd-toed ungulates remained muddled. Now, researchers newfound understanding of Cambaytherium has shed some light on the group's emergence.
The emergence Cambaytherium is largely thanks to a single coal mine in India, just north of Mumbai. For the last decade, researchers there have been excavating hundreds of ancient fossils. Since 2001, the dig site has yielded more than 200 Cambaytherium bones.
"Many of Cambaytherium's features, like the teeth, the number of sacral vertebrae, and the bones of the hands and feet, are intermediate between Perissodactyla and more primitive animals," Ken Rose, a professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine, explained in a press release. "This is the closest thing we've found to a common ancestor of the Perissodactyla order."
Ken's collaborative work with researchers in India was detailed this week in the online journal Nature Communications.
The new Cambaytherium analysis lends credence to long-standing theories that a variety of animals -- including ungulates, rodents, primates and others -- evolved isolated on a floating India.
"Around Cambaytherium's time, we think India was an island, but it also had primates and a rodent similar to those living in Europe at the time," Rose said. "One possible explanation is that India passed close by the Arabian Peninsula or the Horn of Africa, and there was a land bridge that allowed the animals to migrate. But Cambaytherium is unique and suggests that India was indeed isolated for a while."