A North Carolina aquarium says a stingray that got pregnant this winter despite not having shared a tank with a male of her species for many years has died.
(Most animal classes in the animal kingdom have parthenogenetic species, but there are no known cases in mammals that have not been artificially induced.)
It's weird, but it makes sense as a last ditch effort to bridge a population bottleneck. Just because we haven't witnessed something doesn't make it impossible.
I don't mean to suggest it's impossible. Clearly it is possible to artificially induce parthenogenesis in mammals because it has been done, although the offspring have not been healthy so far.