Washington, April 27 : Scientists have discovered a dinosaur tooth along what's now the Kakanaut River of northeastern Russia, a find that shows dinos once lived above the Arctic Circle.

Scientists say the dinosaurs became extinct 65 million years ago when a big meteor crash set off volcanoes galore, with dust and smoke filling up the air.

One theory holds that cold, brought on by the Sun's concealment, is what did them in, but a team of paleontologists led by Pascal Godefroit, of the Royal Belgian Institute of Natural Sciences in Brussels, argues otherwise.

According to them, some dinosaurs (warm-blooded, perhaps) were surprisingly good at withstanding near-freezing temperatures.

The team's latest find, a diverse stash of dinosaur fossils laid down just a few million years before the big impact, along what's now the Kakanaut River of northeastern Russia, is proof of their theory.

Even accounting for continental drift, the dinos lived at more than 70 degrees of latitude north, well above the Arctic Circle.

The scientists also say that the dinosaurs above the Arctic weren't lost wanderers.

The fossils include dinosaur eggshells - a first at high latitudes, and evidence of a settled, breeding population.

But, life was not easy for the dinosaurs during that period.

The size and shape of fossilized leaves found with the bones enabled Godefroit's team to estimate a mean annual temperature of 50 degrees Fahrenheit, with wintertime lows at freezing.

According to the team of scientists, all that dust in the atmosphere must have curtailed photosynthesis everywhere, weakening the base of the food chain and inflicting starvation, and finally extinction, upon the dinosaurs. (ANI)