The article also mentions a reference to a study done on the olm showing that the species may be not one single species but many distinct species that immigrated into the cave system and independently developed similar physical traits or morphology. (Sket, B. 1997. Distribution of Proteus (Amphibia: Urodela: Proteidae) and its possible explanation. Journal of Biogeography 24, 263-280.)
They are even looked at as a national treasure. Slovenia, one of the county's where this species occurs, has even issued currency featuring this salamander.