Lower Carboniferous vs Missippian period

Lower Carboniferous and Missippian period both are nouns.

Word	Noun	Adjective	Verb	Adverb
Lower Carboniferous	Yes	No	No	No
Missippian period	Yes	No	No	No

As nouns, Lower Carboniferous and Missippian period are synonyms defined as:

Lower Carboniferous and Missippian period: the period from 345 million to 310 million years ago; characterized by an increase of land areas, primitive ammonites and winged insects

Other synonyms of Lower Carboniferous include Lower Carboniferous period, Mississippian.

Lower Carboniferous (noun)	Missippian period (noun)
the period from 345 million to 310 million years ago; characterized by an increase of land areas, primitive ammonites and winged insects	the period from 345 million to 310 million years ago; characterized by an increase of land areas, primitive ammonites and winged insects