Giant dog

I read about a breed of dog from Russia called a Medelan is a giant breed once used on royal hunts for bear. This dog was claimed to have been as a puppy, as big as a Great Dane! The adult dog were claimed to have been as big as a calf! These huge ferocious dogs were favored by the last Czar but had been kept by several Czars before him. Unfortunately when the Czar fell from power all of the dogs were killed and the breed is now extinct