There are 8 known species and one isn't seen often due to it being worse of a feeder than C. cornuta and the other could possibly be extinct, but I'm not sure. They are as follows;

Ceratophrys aurita(Brazilian Horned Frog)-rare, but sometimes available. Very high price tag even for babies.

C. calcarata(Venezualan Horned Frog)- trouble feeder.

C. cranwelli(Chacoan Horned Frog)-most available in the trade and most color morphs out there of all species.

C. cornuta(Amazonian/Surinam Horned Frog)- difficult feeder and sometimes hard to find.

C. joazeirensis(Caatinga Horned Frog)-rare, but becoming more available.

C. ornata(Argentine Horned Frog)-not as available as cranwelli, but not hard to find.

C. Stolzmani(Pacific Horned Frog) occationally available.

C. testudo(have never seen this one available anywhere. Thought to be exstinct by some)

I don't have any links available. Just look up the name.