It was discovered several days ago in a sand and gravel pit in the republic of Gorny Altai's northwestern Maimin district, officials said.
Experts believe the prehistoric animal could have been killed by a huge flood about 18,000 years ago, when a large lake in the Chui Steppe overflew its banks, Ria Novosti reported.
"That caused the most massive flood in history, with water moving at a speed of 160 kilometres an hour and covering earth with 490 metres of water," the republic's government said in a report posted on its website.
Remains of extinct animals have previously been found in Altai. In the fall of 2012, mammoth tusks were discovered near the village of Maima, at a depth of over 10 metres.
Mammoths died out about 10,000 years ago during the last ice age.