New research published today on Journal of Vertebrate Paleontology describes a family of fossils that shed light on the origins of perissodactyls ̵1; a group of mammals including horses, rhinoceroses and tapirs. It provides insight into the controversial question of where these hoofed animals evolved, concluding that they arose in or near present day India.
With more than 350 new fossils, 15-year studies put together an almost complete picture of the skeleton anatomy of Cambaytherium – an extinct relative of the perissodactyls living on the Indian subcontinent by nearly 55. million years ago.
The findings include a sheep-sized animal with moderate running ability and intermediate traits between specific perissodactyls and their more general mammalian precursor. Comparing its bones to many other living and extinct mammals shows that Cambaytherium represents a more primitive stage of evolution than any known perissodactyl species, supporting the origin of the group at or near. India – before they dispersed to other continents when the land connection with Asia formed.
This new landmark paper has been selected for publication as part of the prestigious Vertebrate Memories Series, a special annual publication that offers in-depth analysis of dynamic fossils. most important vertebrates.
Cambaytherium, first described in 2005, was the most primitive member of an extinct group that branched off just before the evolution of perissodactyls, providing scientists with unique clues about ancient origins. age and group evolution.
Ken Rose, professor emeritus explained: “Modern orders are Artiodactyla (even ungulates), perissodactyla and primate appeared abruptly in the early Eocene about 56 million years ago across the Northern Hemisphere, but Their geographical origin remains a mystery. at Johns Hopkins University and lead author of the study.
Professor Rose became intrigued by a new theory that suggests that perissodactyls may have evolved in isolation in India. India was an island continent then drifted north, but then it collided with the Asian continent to form a mainland.
“In 1990, Krause and Maas proposed that these orders may have developed in India, in the process it drifted north from Madagascar, dispersing across the northern continents when India collided with the continent. ASIAN.”
With this new theory, Rose and her colleagues received funding from the National Geographic Association to explore India in search of rare fossils containing rocks at the exact age that could provide evidence. important origin of perissodactyls and other mammal groups.
The first trip to Rajasthan in 2001 was unsuccessful, “Although we found only a few fish bones during that trip, the following year our Indian colleague, Rajendra Rana, continued to explore. lignite mines in the south and to the Vastan Mines in Gujarat. “
This new mine shows much more promise. Rose added: “In 2004, our team was able to go back to the mine, where our Belgian collaborator Thierry Smith found the first mammal fossils, including Cambaytherium.”
Encouraged, the team returned to the mine and collected the fossil bones of Cambaytherium and many other vertebrates, despite the challenging conditions.
“The heat, the constant noise and the coal dust in the lignite mines are very difficult – basically, trying to work hundreds of feet down near the bottom of the open-pit coal mines being mined,” he said. waterfall 24/7 “.
Through years of challenging field research, the team can finally unravel a mammal mystery. Despite the abundance of perissodactyls in the Northern Hemisphere, Cambaytherium suggests that this group may have evolved isolated in or near India during the Paleocene (66-56 million years ago), before dispersing into another continent when the land link with Asia takes shape.
Fossils show that the ancestors of horses and rhinos were native to the Asian subcontinent when it was still an island.
Kenneth D. Rose et al., Anatomy, Relationship and Paleontology of Cambaytherium (Mammalia, Perissodactylamorpha, Anthracobunia) from Low Eocene in Western India, Journal of Vertebrate Paleontology (Year 2020). DOI: 10.1080 / 02724634.2020.1761370
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