Regnellidium diphyllum vs regnellidium

Regnellidium diphyllum and regnellidium both are nouns.

Word	Noun	Adjective	Verb	Adverb
Regnellidium diphyllum	Yes	No	No	No
regnellidium	Yes	No	No	No

As nouns, Regnellidium diphyllum and regnellidium are synonyms defined as:

Regnellidium diphyllum and regnellidium: small latex-containing aquatic fern of southern Brazil

Regnellidium diphyllum (noun)	regnellidium (noun)
small latex-containing aquatic fern of southern Brazil	small latex-containing aquatic fern of southern Brazil