spine vs aculeus

spine and aculeus both are nouns.

Word	Noun	Adjective	Verb	Adverb
spine	Yes	No	No	No
aculeus	Yes	No	No	No

As nouns, aculeus is a hypernym of spine; that is, aculeus is a word with a broader meaning than spine:

spine (noun)	aculeus (noun)
a sharp rigid animal process or appendage; as a porcupine quill or a ridge on a bone or a ray of a fish fin	a sharp-pointed process especially a sting of a hymenopterous insect
the part of a book's cover that encloses the inner side of the book's pages and that faces outward when the book is shelved	a stiff sharp-pointed plant process
the series of vertebrae forming the axis of the skeleton and protecting the spinal cord
a small sharp-pointed tip resembling a spike on a stem or leaf
any sharply pointed projection