In 2015, a study recovered mDNA from ancient canid specimens that were discovered on Zhokhov Island and the Yana river, arctic Siberia. These specimens included the mandible of a 360,000–400,000 YBP "Canis c.f. variabilis" (where c.f. is a Latin term meaning uncertain). Phylogenetic analyses of these canids revealed nine mDNA haplotypes not detected before. The "Canis c.f. variabilis" specimen clustered with other wolf samples from across Russia and Asia. The mDNA haplotypes of one 8,750 YBP specimen and some 28,000 YBP specimens matched with those of geographically widely-spread modern dogs. One 47,000 YBP canid from Duvanny Yar (which was once a part of western Beringia) was distinct from wolves but was only a few mutations away from those haplotypes found in modern dogs. The authors concluded that the structure of the modern dog gene pool was contributed to from ancient Siberian wolves and possibly from "Canis c.f. variabilis".