Thaumosaurs

For obvious reasons, most fantasy settings include the range of mundane beasts of vaious sorts: lions, tigers, and bears...

Equally obviously, most fantasy settings also include a range of magical beasts: dragons, unicorns, etc. Of course this makes sense, since in a magical universe you would expect too see creatures evolve magical capabilities as well as mundane ones.

Since dinosaurs are cool, a lot of fantasy settings also include regions where these creatures have not become extinct for whatever reason. And so PCs can find themselves going up against Tyrannosaurs, Velociraptors, and the rest. These represent an earlier branch of evolution, and are no bad thing in a setting.

But...

If you put those latter two together, you get a fourth segment of that square: what about those creatures that were part of that "earlier branch of evolution", but which were also those to evolve magical capabilities as well as mundane ones?

So that's the next thing on my to-do list: create the thaumosaurs - the magical beast equivalents for the mundane dinosaurs. Which, of course, will then probably never be used.