Species that developed while India moved from Gondwana to Asia

About 200 million years ago the land mass that is now the India plate was part of Gondwanaland. When this plate broke off from Gondwana around 135 million years ago it included what is now Madagascar but then left Madagascar behind as it began – by tectonic standards – a headlong rush north-eastwards around 90 million years ago. Till the collision of this plate with Asia around 10 million years ago brought about the formation of the Himalayas. For around 80 million years then the Indian land mass was an isolated island “rushing” north-east at between 16-20 cm/year!

From Gondwanaland to modern times image berkeley.edu

Indian plate tectonics (after Wikipedia)

(after wikipedia)

 

This period was also extraordinarily rich in the evolutionary history of the mammals. It was the time when snakes and ants first appeared. There was a mass extinction event about 66 million years ago. The dinosaurs disappeared and became birds. Birds proliferated and so did large flightless birds. The diversity of mammals exploded, perhaps just because of the space left by the disappearance of the large, unsuccessful dinosaurs. The first pigs and deer developed. The grasses arrived. Carnivorous mammals appeared as their prey increased. The first primates made an entrance. But whatever was evolving on the Indian land-mass was evolving largely in isolation from that taking place in the areas that were to become Africa and Eurasia. But there are tantalising indications that on its journey the Indian land-mass may have been connected for short periods by a land bridge to the Horn of Africa or to what is now Arabia.

A new paper reports on fossils from the edges of an open cast coal mine north east of Mumbai in Western India.

Kenneth D. Rose, Luke T. Holbrook, Rajendra S. Rana, Kishor Kumar, Katrina E. Jones, Heather E. Ahrens, Pieter Missiaen, Ashok Sahni, Thierry Smith. Early Eocene fossils suggest that the mammalian order Perissodactyla originated in India. Nature Communications, 2014; 5: 5570 DOI: 10.1038/ncomms6570

The results suggest that an ancient relative of horses and rhinos lived 54.5 million years ago in what is now India. The findings shed light on the evolution of this group of animals. Several groups of mammals that appear at the beginning of the Eocene, including primates and odd- and even-toed ungulates, might have evolved in India while it was isolated.

John Hopkins Press ReleaseWorking at the edge of a coal mine in India, a team of Johns Hopkins researchers and colleagues have filled in a major gap in science’s understanding of the evolution of a group of animals that includes horses and rhinos. That group likely originated on the subcontinent when it was still an island headed swiftly for collision with Asia, the researchers report Nov. 20 in the online journal Nature Communications.

Modern horses, rhinos and tapirs belong to a biological group, or order, called Perissodactyla. Also known as “odd-toed ungulates,” animals in the order have, as their name implies, an uneven number of toes on their hind feet and a distinctive digestive system. Though paleontologists had found remains of Perissodactyla from as far back as the beginnings of the Eocene epoch, about 56 million years ago, their earlier evolution remained a mystery, says Ken Rose, Ph.D., a professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine.

An artist’s depiction of Cambaytherium thewissi via Science Daily Credit: Elaine Kasmer

The mine yielded what Rose says was a treasure trove of teeth and bones for the researchers to comb through back in their home laboratories. Of these, more than 200 fossils turned out to belong to an animal dubbed Cambaytherium thewissi, about which little had been known. The researchers dated the fossils to about 54.5 million years old, making them slightly younger than the oldest known Perissodactyla remains, but, Rose says, it provides a window into what a common ancestor of all 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,” Rose says. “This is the closest thing we’ve found to a common ancestor of the Perissodactyla order.”

Cambaytherium and other finds from the Gujarat coal mine also provide tantalizing clues about India’s separation from Madagascar, lonely migration, and eventual collision with the continent of Asia as the Earth’s plates shifted, Rose says. In 1990, two researchers, David Krause and Mary Maas of Stony Brook University, published a paper suggesting that several groups of mammals that appear at the beginning of the Eocene, including primates and odd- and even-toed ungulates, might have evolved in India while it was isolated. Cambaytherium is the first concrete evidence to support that idea, Rose says. But, he adds, “It’s not a simple story.”

“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,” he says. “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.”

 

 

 

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