WWF has more fun facts about snow leopards.

Davis, Li and Murphy (2010) “Supermatrix and species tree methods resolve phylogenetic relationships within the big cats, Panthera (Carnivora: Felidae)” looks at several earlier works on big cat phylogeny and discusses some issues with them, mainly that they couldn’t agree on the same topology. Through their own data-analysis they “yield a robust consensus topology supporting the monophyly of lion and leopard, with jaguar sister to these species, as well as a sister species relationship of tiger and snow leopard.”