bottle-nosed dolphin vs bottlenose dolphin

bottle-nosed dolphin and bottlenose dolphin both are nouns.

Word	Noun	Adjective	Verb	Adverb
bottle-nosed dolphin	Yes	No	No	No
bottlenose dolphin	Yes	No	No	No

As nouns, bottle-nosed dolphin and bottlenose dolphin are synonyms defined as:

bottle-nosed dolphin and bottlenose dolphin: any of several dolphins with rounded forehead and well-developed beak; chiefly of northern Atlantic and Mediterranean

Other synonyms of bottle-nosed dolphin include bottlenose.

bottle-nosed dolphin (noun)	bottlenose dolphin (noun)
any of several dolphins with rounded forehead and well-developed beak; chiefly of northern Atlantic and Mediterranean	any of several dolphins with rounded forehead and well-developed beak; chiefly of northern Atlantic and Mediterranean