Fuligo septica is not a true fungus, but a form of slime mold that is actually a lower life form than fungus.
From the ocregister.com
The oomycetes are not true fungi but are fungus-like organisms.
From the en.wikipedia.org
Yes, something this delicious is in fact a fungus and not a true vegetable, but not even an unattractive name can keep me away from this tasty treat.
From the newsobserver.com
It was in the 19th Century that the true nature of lichens, as organisms consisting of an alga and a fungus in specific association, was demonstrated by Schwendener in 1867.