dead-men's-fingers vs fungus

dead-men's-fingers and fungus both are nouns.

Word	Noun	Adjective	Verb	Adverb
dead-men's-fingers	Yes	No	No	No
fungus	Yes	No	No	No

As nouns, fungus is a hypernym of dead-men's-fingers; that is, fungus is a word with a broader meaning than dead-men's-fingers:

dead-men's-fingers: the fruiting bodies of the fungi of the genus Xylaria
fungus: an organism of the kingdom Fungi lacking chlorophyll and feeding on organic matter; ranging from unicellular or multicellular organisms to spore-bearing syncytia

dead-men's-fingers (noun)	fungus (noun)
the fruiting bodies of the fungi of the genus Xylaria	an organism of the kingdom Fungi lacking chlorophyll and feeding on organic matter; ranging from unicellular or multicellular organisms to spore-bearing syncytia