How did the hammerhead shark evolve?

Ordinary shark crossed with a t-bone steak innit

maybe the mouth just got flattened and wider to break up coral or whatever with evoloution, or maybe God just thought, "wouldn't it be cool to have a shark with a head like a hammer".
The latter for me :)

blame the nail fish

Surely the Hammer head shark was around before the Hammer?? so what was it called before the hammer was invented?

Sphyrna lewini (NAP)

marmota monax

Cruises over sand and reefs in search of prey. Pins stingrays to the sand with hammer whilst disabling them.

The Valuev of the shark world.