Retrosaur 9

Erikidorsus (hedgehog back) lived during the early/mid Jurassic and was either a very ancient member or a bizarre offshoot of the Spike Tail family. Had a special organ within it’s lower spine to act as a ‘second brain’ in order to give it enough fine control over its tail, to that point that the tail was quasi-prehensile. How did this this thing mate? Most paleontologists agree that they don’t know.

Based on this piece of paleoart, which allegedly depicts a stegosaur.