This puzzle starts as a simple crossword. All of the given body parts can be found in the grid like so:
The letters which are not part of any word spell out the message YOU HAVE A SKULL, YET WHERE ARE THE CROSSBONES? THERE YOU WILL FIND YOUR ANSWER. This hints that solvers should look for crossbones – that is, places where bones cross. Highlighting only the bones in the grid gives this:
The bone names cross or overlap in exactly seven places. From top to bottom, these crossing letters spell out the answer FOSSILS.