Ursus horribilis vs Ursus arctos horribilis

Ursus horribilis and Ursus arctos horribilis both are nouns.

Word	Noun	Adjective	Verb	Adverb
Ursus horribilis	Yes	No	No	No
Ursus arctos horribilis	Yes	No	No	No

As nouns, Ursus horribilis and Ursus arctos horribilis are synonyms defined as:

Ursus horribilis and Ursus arctos horribilis: powerful brownish-yellow bear of the uplands of western North America

Other synonyms of Ursus horribilis include grizzly, grizzly bear, silver-tip, silvertip.

Ursus horribilis (noun)	Ursus arctos horribilis (noun)
powerful brownish-yellow bear of the uplands of western North America	powerful brownish-yellow bear of the uplands of western North America