Never meant to imply that any style of pizza was more authentic than any other, but I do know that it would be difficult to find information about the origins of Napolitan pizza without acknowledging that Naples used to be a part of Spain/Kingdom of Aragon. The history of pizza is intertwined and inseparable from the history of cocas, cocques (the name itself is over a thousand years old). I used to have great chats with Toni from the Llorens bakery in Alicante about the local food and its origins and how little there is documenting the food eaten by ordinary people in history. Seems word of his passion spread so a film crew came round and he gives a run down of what he's learned over the years, including his understanding of what a historical coca/pizza would be like. There is a huge, enormous variation in cocas today, they are still eaten across Spain, including on the Eastern Coast as well as in Mallorca and the other Mediterranean Islands. Cocas, as a Spaniard would recognise them, are also still eaten in Italy. Seems to me that the Pizza Romana or Rustica branched off from the coca tradition in different ways and at different times to the Neopolitan style pizza, the Romana/rustica style does appear to bear just a little more resemblance to a coca.

Even if you don't speak Spanish, Toni's recreation of an ancient coca is quite interesting (I think so, anyway)
http://m.youtube.com/watch?v=diFm-c3_b54