Which is extinct, the Russian tracker or Norfolk Terrier.?
Russian tracker The Russian Tracker or Russian Retriever is an extinct breed of domestic dog. It is uncertain when precisely the breed ceased to exist; it could still be found in the late 1800s. The Tracker was of Asiatic Russian origin. It was used for hundreds of years to protect and herd the flocks of the Indo-Aryan people in the wind-beaten, snow-swept Caucasus Mountains.
Vietnam mouse-deer The Vietnam mouse-deer (Tragulus versicolor), also known as the silver-backed chevrotain, is a species of even-toed ungulate in the family Tragulidae that at present only is known from Vietnam. Until 2004, it was generally treated as a subspecies of the greater mouse-deer ("T. napu"), though it more closely resembles the lesser mouse-deer ("T. kanchil"). Recent records of this very poorly known species are missing, but this is more likely due to the difficulty involved in separating it from other mouse-deer and the general absence of field work within its presumed range than it being extinct. The Silver-backed Chevrotain is among the 25 “most wanted lost” species that are the focus of Global Wildlife Conservation’s “Search for Lost Species” initiative.