A fossil shell is filled with mud. The shell dissolves, leaving an impression of its inside surface on the shell- filling lump of mudstone. What type of fossil is this?

Question

Quizplus · Accepted Answer

This is an example of an internal mould, where the internal structure of the organism is preserved as an impression after the original biological material has dissolved away, leaving behind a cast of its internal features in the sediment that filled it.

A Fossil Shell Is Filled with Mud