Missippian period vs Lower Carboniferous

Missippian period and Lower Carboniferous both are nouns.

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

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

Missippian period and Lower Carboniferous: 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 Missippian period include Lower Carboniferous period, Mississippian.

Missippian period (noun)	Lower Carboniferous (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