Via BBC Science:
... Now, exquisite X-ray images featured in Science magazine are providing new insights on how the ammonites lived and perhaps also on why they died out...
They reveal the mouthparts of three ammonite specimens discovered in Belle Fourche, South Dakota, US, a place renowned for the excellent preservation of fossils.
The fossils are actually from a grouping of straight, or uncoiled, ammonites known as Baculites but the implications should hold across a great swathe of species.
Beautiful 3D reconstructions lay bare the physical characteristics of the molluscs' jaws and a tongue-like structure called the radula...