We think it’s more likely that ammonites would have had eight arms rather than lots of tentacles like a nautilus, though the shell is more similar to that of a nautilus.' Ammonites were born with tiny ...

The half-cut shell of the modern Nautilus (right). 3D-printed half-cut ammonite shell (left). Chamber model from the current study, cut to show internal geometry (top). Disclaimer: AAAS and ...

Based on the fossil record, ammonites came in a wide range of sizes and shapes, from smaller than an inch to as large as nine feet wide. Some ammonites had long, straight shells, while others had ...