Sexing by skull shape?

[lovenokia]

So I couldn't quite get the angle right, but as you can see these two greens are roughly the same length but have different head shape/size. The one on the left has a much wider head and a longer snout. I've been thinking that the individual on the left is a female, and the one on the right is a male. What do you think?

My frog looks exactly like the one on the right, the darker colored frog.
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