Since 2001, for two weeks at a stretch, every year or two, a team of researchers from Johns Hopkins University dug in an open-pit coal mine in India, northeast of Mumbai. The site was bountiful, to say the least, yielding a vast collection of bones.
Among those bones were in excess of 200 fossils from a previously little-documented animal called Cambaytherium thewissi. The bones were dated to about 54.5 million years old.
What was so special about a couple of hundred really old bones in a mine in India? The researchers consider them the closest thing yet seen to a common ancestor of Perissodactyla-- the group to which modern horses, tapirs, and rhinos belong.
"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 lead researcher Ken Rose, Ph.D., a professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine, in a release.
Paleontologists already have a fairly long view of Perissodactyla -- fossils from the group have been described as far back as about 56 million years ago, at the beginning of the Eocene. But the group's earlier evolution remained a mystery. While the Cambaytherium bones are a bit younger than the oldest of those already known fossils, the Johns Hopkins team says Cambaytherium provides a window into what a common ancestor of all Perissodactyla would have looked like (see photo above for a depiction).
In addition to opening a wider window onto the ancestry of modern rhinos and horses, the scientists say the Cambaytherium thewissi fossils also represent the first evidence to support the notion that several groups of mammals from the early Eocene might have evolved on the Indian subcontinent while it was still isolated at sea and had not yet smashed into Asia. That idea was first posed in a 1990 paper by David Krause and Mary Maas, of Stony Brook University.
Read more at Discovery News
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