Yep, thats the problem they are all very very similar looking. as far as I am concerned it is most likely oplurus cuvieri. which is cool because I have read that they tame down well with regular handling. the south and central american spiny iguanas tend to be more aggressive and a challenge to tame.
its a shame that I still can't find a whole lot of information about the madagascan spiny tail either. would be nice to find a caresheet or something. are they a pretty uncommon species? cause I might consider trying to breed them if there would be a demand for offspring.
can I also confirm with you guys, the 2 pictures i posted are of two males. I have a suspicion that they are two seperate species or do you guys think that they are both definately Oplurus cuvieri?