Fossil Nautiloid, Orthoceras sp., dating to around 350 Million Years ago , from Morocco. 15cm These interesting sea creatures have a present-day equivalent in the chambered nautilus shells of the modern squid . While modern shells curve, these ancient versions were ‘straight’. Cut & polished out of a black marble stone, you can still see their internal shell divisions in dramatic detail. These chambers could be either filled with air to give buoyancy – or with water to allow diving – much like modern submarines!