Marco Polo's sheep vs Marco Polo sheep

Marco Polo's sheep and Marco Polo sheep both are nouns.

Word	Noun	Adjective	Verb	Adverb
Marco Polo's sheep	Yes	No	No	No
Marco Polo sheep	Yes	No	No	No

As nouns, Marco Polo's sheep and Marco Polo sheep are synonyms defined as:

Marco Polo's sheep and Marco Polo sheep: Asiatic wild sheep with exceptionally large horns; sometimes considered a variety of the argali (or Ovis ammon)

Other synonyms of Marco Polo's sheep include Ovis poli.

Marco Polo's sheep (noun)	Marco Polo sheep (noun)
Asiatic wild sheep with exceptionally large horns; sometimes considered a variety of the argali (or Ovis ammon)	Asiatic wild sheep with exceptionally large horns; sometimes considered a variety of the argali (or Ovis ammon)