shovelhead vs hammerhead shark

shovelhead and hammerhead shark both are nouns.

Word	Noun	Adjective	Verb	Adverb
shovelhead	Yes	No	No	No
hammerhead shark	Yes	No	No	No

As nouns, hammerhead shark is a hypernym of shovelhead; that is, hammerhead shark is a word with a broader meaning than shovelhead:

shovelhead: small harmless hammerhead having a spade-shaped head; abundant in bays and estuaries
hammerhead shark: medium-sized live-bearing shark with eyes at either end of a flattened hammer-shaped head; worldwide in warm waters; can be dangerous

Other hypernyms of shovelhead include hammerhead.

shovelhead (noun)	hammerhead shark (noun)
small harmless hammerhead having a spade-shaped head; abundant in bays and estuaries	medium-sized live-bearing shark with eyes at either end of a flattened hammer-shaped head; worldwide in warm waters; can be dangerous