Siamang gibbon. Credit: WCS Indonesia Program/C Bransilver
New Delhi, April 26: Scientists have labelled two fossilised teeth from nine million years ago recovered from India's Sivalik hills as fresh evidence for an extinct primate named Krishnapithecus first proposed 38 years ago.
Indian and US scientists who studied the two infant molar teeth have said the fossils belong to a species that represents an independent family within the extinct primates called pliopithecines that lived in Asia and Europe between 25 million and 10 million years ago.
Their study has indicated that Krishnapithecus weighed about 15kg and was slightly larger than the modern black-furred Siamang gibbons found in present-day Malaysia, Thailand and Sumatra.
"On the primates' evolutionary tree, Krishnapithecus represents one of the lineages that led to the modern Siamang gibbons," said Anek Ram Sankhyan, a senior scientist formerly with the Anthropological Survey of India.
Scientists believe Krishnapithecus was contemporary to Sivapithecus and Indopithecus, two extinct apes that had lived in the northern Indian subcontinent between 12 million and six million years ago.
Sankhyan collaborated with Terry Harrison at New York University and Jay Kelly at the University of Arizona to study the fossilised teeth which he had found embedded in clay deposits near Haritalyangar, Himachal Pradesh, nearly five years ago.
In a paper published in the Journal of Human Evolution, the scientists have said the molars suggest that Krishnapithecus "was perhaps the largest known pliopithecoid" and it was "sufficiently distinct" from other pliopithecoids to be classified as a separate family.
Two anthropologists from Panjab University, Chandigarh, had first proposed the existence of an independent pliopithecoid in 1979 on the basis of a single molar tooth they had recovered, also from a site near Haritalyangar.
"That tooth was the first evidence of something new," said Rajan Gaur, professor at the department of anthropology at Panjab University. "At the time, it was also the first fossilised ancestor of a gibbon. The new fossils would provide additional supporting evidence."
A senior geologist at Panjab University who has earlier conducted research on Indopithecus said the new evidence for Krishnapithecus is also significant because it shows pliopithecines were around longer than previously believed.
"Based on fossil evidence from Europe, it was earlier thought that pliopithecines had gone extinct by 11 million years," Rajeev Patnaik, professor of geology, told The Telegraph. "But now we know pliopithecines survived here at least until nine million years ago."
Sankhyan and his collaborators say the teeth they studied are smaller than those of Sivapithecus and belonged to a primate slightly larger than the living Siamang gibbon that typically weighs 9kg to 13kg. They have also described their findings in Current Science, a journal from the Indian Academy of Sciences.
The pliopithecus apes as well as the Sivapithecus and Indopithecus predated the emergence of the great apes, the chimpanzee, the gorilla and the orang-utan. But some scientists have argued that Sivapithecus was an ancestor of the modern orangutan.
"Krishnapithecus was a primitive, distant cousin of Sivapithecus," said Harrison. " Sivapithecus is more closely related to humans than it is to Krishnapithecus. Sivapithecus was similar in size to modern great apes."