Researchers have gained important insight into the evolution of a group of animals that includes horses and rhinos.
The biological group, dubbed Perissodactyla, most likely originated in what is now India when it was an island on a collision course with Asia, Johns Hopkins Medicine reported. Remains of animals in this group have been traced back as far as 56 million years ago, but their evolution before that time has remained a mystery.
Researchers excavated a mine near Mumbai that held a wealth of ancient teeth and bones, 200 of which belonged to the 54.4 million-year-old Cambaytherium thewissi. The findings provide insight into what early Perissodactyla would have looked like.
"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," said Ken Rose, a professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine. "This is the closest thing we've found to a common ancestor of the Perissodactyla order."
The findings could not only provide insight into early links in the evolutionary chain, but could also reveal details of India's separation from Madagascar and eventual collision with Asia. Researchers have suggested several groups of animals, including primates and even odd-toed ungulates (Perissodactyla) may have evolved in India when it was still isolated; the Cambaytherium is the first evidence to back up that idea.
"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."
The findings were published Nov. 20 in the journal Nature Communications.
