A recent journal article detailing the diploid and octoploid relationships between Pacman Frogs (Horned Frogs), particularly the Chacoan Horned Frog (Ceratophrys cranwelli) and Ornate Horned Frog (Ceratophrys ornata).

http://www.bioone.org/doi/abs/10.2994/SAJH-D-14-00032.1

You can get the full article from the authors here:

https://www.researchgate.net/profile...tophryidae.pdf