crustose thallus vs thallus

crustose thallus and thallus both are nouns.

Word	Noun	Adjective	Verb	Adverb
crustose thallus	Yes	No	No	No
thallus	Yes	No	No	No

As nouns, thallus is a hypernym of crustose thallus; that is, thallus is a word with a broader meaning than crustose thallus:

crustose thallus: thin crusty lichen thallus; adheres closely to or is embedded in the surface on which it grows
thallus: a plant body without true stems or roots or leaves or vascular system; characteristic of the thallophytes

crustose thallus (noun)	thallus (noun)
thin crusty lichen thallus; adheres closely to or is embedded in the surface on which it grows	a plant body without true stems or roots or leaves or vascular system; characteristic of the thallophytes