P. imperator vs. P. dictator

[Terrena Laxamentum]

I know that with the recent shipments of certain large, black scorpions with lustrous sheens that there has been some debate whether they are Dictators or Emperors. This isn't a topic asking what I have, but more asking about the specific differences between the two. I have heard that Dictator have a far more granulated look and that Imperator has a triangular indentation towards the back of the head. One of my co-workers also stated that their tails look different (I have never heard of said difference, so I don't know how true that is).