These also add to the size and blocky shape of the head. Here is a photo of Jake, a mature male. Notice the fatty bumps behind the eye and above the ear. This is Brownie, who is also a mature male. This photo, taken from underneath the chin, gives a great view of the swollen jowls.
Males also tend to have longer dorsal spikes along their back, especially along the neck area.
Another indication that an iguana is a male is the large pores that are visible along the inner thigh. These pores, called femoral pores, are easily visible in males, and are often filled with a waxy substance. Here is another photo of Jake. Notice his large, easily visible femoral pores. This photo was taken when Jake was not in breeding season.