Board Thread:General Discussion/@comment-27441478-20161211142759/@comment-679780-20161213142938

Shadow and Silver are in a sense, unique cases.

Shadow is an artificially created lifeform, cloned from Hedgehog and Black Dooms DNA which means he could be a unique species of hedgehog.

Silver, while I believe is more hedgehog than Shadow, it is believed his psychokinesis is due to evolution, so he could be a brand new species of hedgehog yet to exist on Sonic's world.

But I believed my previous post is a more accurate estimation who species of hedgehog they all are.