Xenon's Seventh Circle

There's some remarkable talent in palaeontology, although of course the current lot have some great pioneers to thank. Basically, if you have enough of the skeleton to go on, you can look at the variations. Things like joints, teeth, horns, etc. There's a lot of pure luck involved though. When you consider the destructive effects of plate tectonics, it's remarkable that anything survives long enough to be found! And plenty of stuff works its way to the surface, and just weathers away before it can be found.