pen-tail vs tree shrew

pen-tail and tree shrew both are nouns.

Word	Noun	Adjective	Verb	Adverb
pen-tail	Yes	No	No	No
tree shrew	Yes	No	No	No

As nouns, tree shrew is a hypernym of pen-tail; that is, tree shrew is a word with a broader meaning than pen-tail:

pen-tail: brown tree shrew having a naked tail bilaterally fringed with long stiff hairs on the distal third; of Malaysia
tree shrew: insectivorous arboreal mammal of southeast Asia that resembles a squirrel with large eyes and long sharp snout

pen-tail (noun)	tree shrew (noun)
brown tree shrew having a naked tail bilaterally fringed with long stiff hairs on the distal third; of Malaysia	insectivorous arboreal mammal of southeast Asia that resembles a squirrel with large eyes and long sharp snout