Elasmotherium sibiricum
If you google the name of this beast, most of the drawings show a much different looking image of this animal....
The Image in the article looks more like a horse, most of the google images look like a rhino...
Some of those images look like bison with a horn.
Rhinos are unichorns to aren't they
If they found one from 29kya, perhaps there were even a few that survived up to the time of historical/mythological memory.