The Hindu : National : World's oldest fossil of rodent discovered in Jaisalmer

Online edition of India's National Newspaper
Friday, Nov 25, 2005

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World's oldest fossil of rodent discovered in Jaisalmer

Special Correspondent

Believed to have existed during the Cretaceous age of the Mesozoic era The find indicates to the topography of rivers, valley and wetland during the Cretaceous age in western Rajasthan, which is now a desert.

JAIPUR: The Geological Survey of India on Thursday announced the discovery of "the world's oldest fossil of a rodent belonging to the period ranging from 93.2 million to 142 million years ago."

The fossil of the rodent's tooth forms part of a micro-vertebrate fossil assemblage unearthed in Jaisalmer district of Rajasthan.

The fossils, which were discovered in a three-month field exploration early this year, were believed to have existed during the Cretaceous age of the Mesozoic era. The discovery is expected to provide vital links to the evolutionary lineage of these animals.

In addition to the remains of an upper molariform tooth supported by five roots of the oldest rodent mammal, a complete mandibular jaw with 13 pleurodontid teeth of a lizard, and eight fin-ray fish scales were discovered.

P. M. Dutta, director, Palaeontology Division in the GSI's western region, told reporters here that the rodent mammal fossil, found in the Parewar region of Jaisalmer basin, was the world's earliest record of a rodent. "In all probability, it was a small mouse," said Mr. Dutta.

Mr. Dutta, who carried out exploration in the region during January to March this year, said the length of the tooth was 1.05 mm and width 0.75 mm.

The presence of a rodent fossil in the territory, combined with the evidence of lizard and fish inhabiting the region, indicates to the topography of rivers, valley and wetland during the Cretaceous age in western Rajasthan, which is now a sprawling desert.

The find is the first systematic record of the Mesozoic vertebrate fossils from the State containing the three major groups — mammal, reptile and fish — of animals with spinal column. The GSI expects that the discovery would place the Jaisalmer basin prominently on the world's fossil atlas.

Will compensate

paucity

Mr. Dutta said the fossil of iguanian lizard, found in the Sanu region of Jaisalmer basin, would compensate the paucity of the lizard fossil record from the southern continents in comparison with that of the northern continents. The Rajasthan lizard has also suggested the southern origin of the squamate reptile.

The discovery of fossils at a shallow level around Jaisalmer also indicates that the rocks in the region might not have a significant presence of oil.

Oil has been detected recently in huge quantity in the neighbouring Barmer district.

Mr. Dutta said about 1.5 tonnes of matrix was collected by excavation at Parewar and Sanu and scientifically analysed. The residue yielded the remarkable fossils as well as numerous unidentified skeletal remains.

The GSI expert and deputy director-general R.S. Goyal expressed the hope that the fossil collection would provide corroborative evidence on the origin and age of animals and help in the reconstruction of palaeo-biogeography and palaeo-ecology of the Cretaceous world.

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