Upper Carboniferous period vs Pennsylvanian period

Upper Carboniferous period and Pennsylvanian period both are nouns.

Word	Noun	Adjective	Verb	Adverb
Upper Carboniferous period	Yes	No	No	No
Pennsylvanian period	Yes	No	No	No

As nouns, Upper Carboniferous period and Pennsylvanian period are synonyms defined as:

Upper Carboniferous period and Pennsylvanian period: the period from 310 million to 280 million years ago; characterized by warm climate and swampy land

Other synonyms of Upper Carboniferous period include Pennsylvanian, Upper Carboniferous.

Upper Carboniferous period (noun)	Pennsylvanian period (noun)
the period from 310 million to 280 million years ago; characterized by warm climate and swampy land	the period from 310 million to 280 million years ago; characterized by warm climate and swampy land