callipygous vs callipygian

callipygous and callipygian both are adjectives.

Word	Noun	Adjective	Verb	Adverb
callipygous	No	Yes	No	No
callipygian	No	Yes	No	No

As adjectives, callipygous and callipygian are synonyms defined as:

callipygous and callipygian: pertaining to or having finely developed buttocks

callipygous (adjective)	callipygian (adjective)
pertaining to or having finely developed buttocks	pertaining to or having finely developed buttocks