Now named Dogor, a local word for friend, it was found near Yakutsk in eastern Siberia last summer.
The male’s nose, teeth and fur are in remarkable condition.
It is “possibly the oldest dog ever found”, researcher Love Dalen said, adding that it was “amazingly well-preserved even before they cleaned it up”.
It feels like a “very recently dead animal”, he said.
The body’s age was measured by carbon dating its rib bone, but DNA tests have not confirmed its lineage.
David Stanton, a researcher at the Centre for Palaeogenetics in Sweden, said it was “normally relatively easy” to tell the difference between a dog and a wolf.
“We have a lot of data from it already, and with that amount of data, you’d expect to tell if it was one or the other,” he told CNN.
“The fact that we can’t might suggest that it’s from a population that was ancestral to both dogs and wolves.”
It is suspected that Dogor is from a time when dogs became domesticated, leading Mr Stanton to suggest he may be “halfway between” dogs and wolves.
That would chime with research published in the journal Nature Communications in 2017, which said dog domestication appeared to happen between 20,000 and 40,000 years ago.
The year before, an Oxford University study, published in the journal Science, said dogs had been domesticated twice, in Europe and Asia.