The taxonomic position of Przewalski 's horse has always been problematic and no consensus exists whether it is a full species ( Equus przewalskii ) , a subspecies of the wild horse ( Equus ferus przewalskii ) , or even a sub-population of the horse ( Equus ferus ) .
Przewalski 's horse is a rare and endangered subspecies of the wild horse , Equus ferus .