common iguana vs Iguana iguana

common iguana and Iguana iguana both are nouns.

Word	Noun	Adjective	Verb	Adverb
common iguana	Yes	No	No	No
Iguana iguana	Yes	No	No	No

As nouns, common iguana and Iguana iguana are synonyms defined as:

common iguana and Iguana iguana: large herbivorous tropical American arboreal lizards with a spiny crest along the back; used as human food in Central America and South America

Other synonyms of common iguana include iguana.

common iguana (noun)	Iguana iguana (noun)
large herbivorous tropical American arboreal lizards with a spiny crest along the back; used as human food in Central America and South America	large herbivorous tropical American arboreal lizards with a spiny crest along the back; used as human food in Central America and South America