are there buildable units not on the tech tree?

[Mr White]

In my last english campaign, I could build turcopoles in palestine or somewhere in that area. It wasn't on my tech tree (the one on this site) so I was pleasantly surprised that I could build horse archers. This was a lucky break as the required buildings where there allready and I wasn't planning on building them.

Are there other 'hidden' units in the game?

[Mithrandir]

Well you can dismount certain knights, these could be considered "hidden" since you can't train them directly :).

[Ludens]

In my last english campaign, I could build turcopoles in palestine or somewhere in that area. It wasn't on my tech tree (the one on this site) so I was pleasantly surprised that I could build horse archers. This was a lucky break as the required buildings where there allready and I wasn't planning on building them.

Are there other 'hidden' units in the game?
No, though the tech tree that comes with the game is rather bad. Turcopoles can be built by all Catholic factions in Edessa, Antioch (valour bonus), Tripolis and Syria.