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).

3D-printed ammonite shell (left) and nautilus shell (right) show their respective complexities. Image: David Peterman. ... Peterman’s team 3D-printed models of ammonite and nautilus shells.

A cross section of a chambered nautilus shell shows the newly defined shape, the "soft cell," repeating outward in a spiral. FlamingPumpkin via Getty Images When humans cover a space using tiles ...

As the nautilus matures and grows, it periodically seals off the shell behind it and creates a new, larger living chamber. The shells of adults may have as many as 30 such chambers.