brachycephalic vs brachycranial

brachycephalic is a noun but brachycranial is not a noun.

Word	Noun	Adjective	Verb	Adverb
brachycephalic	Yes	Yes	No	No
brachycranial	No	Yes	No	No

As adjectives, brachycephalic and brachycranial are synonyms defined as:

brachycephalic and brachycranial: having a short broad head with a cephalic index of over 80

Other synonyms of brachycephalic include brachycranic.

brachycephalic (noun)	brachycranial (noun)
an adult with a short broad head

brachycephalic (adjective)	brachycranial (adjective)
having a short broad head with a cephalic index of over 80	having a short broad head with a cephalic index of over 80