Can you help me with a layman’s explanation of how paleontologists will take just the skull of an unknown animal – then figure out what it looked like and how it lived. Say the Pakicetus for example.

This is a re-submit. Actually this is my son's question to me, I picked the area of Science history, because my original answer to him (after he studies whale evolution) was that they can "map genomes and stuff" - - I have no idea if that's right, and I'd love to give a better answer - including how they did it before DNA studies.

Actually genomes have nothing to do with this. You have an exalted idea of what we can tell from a genome! You can't get anatomy from a genome (yet), and you can't get a genome from a fossil, anyhow.

Paleoartists (and paleontologists) are, first and foremost, excellent anatomists. In reconstructing a dead animal, they work from fossils -- which have marks on them indicating muscle attachments and other soft structures such as blood vessels and beaks -- and from careful study of living animals and how they move and are put together.

If they don't have a complete skeleton (such as your example of "just the skull") scientists and artists will work from their knowledge of related animals to fill in the missing material. The caricature is that paleontologists conjecture entire animals from just a tooth or a small piece of bone, but the truth is that they are much more conservative than that.

There's a pretty thorough discussion of the process that is currently available online, in the Medill Reports of the Medill School of Journalism at Northwestern University.

For more, try this Google search.

Dan Berger