Northernmost Record of the Merck's Rhinoceros Stephanorhinus kirchbergensis (Jager) and Taxonomic Status of Coelodonta jacuticus Russanov (Mammalia, Rhinocerotidae)

A lower jaw of Stephanorhinus kirchbergensis from the Mus Khaya locality on the Yana River in Yakutia is described. This jaw was previously designated as a paratype of Coelodonta jacuticus, but morphological and morphometric analysis has shown that it actually belongs to a typical S. kirchbergensis. Morphometric parameters of the holotype (skull) of C. jacuticus fall within the range of intraspecific variation of C. antiquitatis. The same results of a morphometric study were obtained for the subspecies Coelodonta antiquitatis pristinus and C. a. humilis. This suggests that C. jacuticus, Coelodonta antiquitatis pristinus, and C. a. humilis are invalid taxa which should be regarded as junior synonyms of C. antiquitatis. The find of S. kirchbergensis in northern Yakutia is the northernmost occurrence of this species.