The ammonite is an odd creature, it looks quite archaic to be honest and that's because it is extinct. The ammonite was quite literally a squid with a shell. It was indeed carnivorous, it's closest living ancestor is the squid.

Ammonite


 

Ammonites died out hundreds of years ago, under unknown circumstances, but they are perhaps the most common fossils people tend to find. So, if you ever find an ammonite fossil, don't be too proud, they are pretty much worthless :)

Back in the day, when more primitive people found the ammonite , they assumed it was a coiled up snake, turned to stone. People usually thought such things were cursed, and associated possessors with witchcraft.

Nevertheless, some of these things were the size of great white sharks, and they were strictly carnivorous, so we should be glad they are not around anymore :) Imagine being grappled by one's tentacles, and eaten, not even harpoons could pierce it's massive shell, there would be no saving you! And it's sharp beak would rip you apart in seconds.

Man compared to ammonite