Mascroscaphites

Ammonites can amaze us with their bizarrely shaped shells, which often came about close to the many great crises they suffered during the long 300-million-year life. Macroscaphites starts off as a normal ammonite rolled up in planispiral shape, then straightening out and ending with a hooklike bend. The planispiral, gas-filled part kept the shell stable in the water, while the organism itself lived in the hooklike section.