Male with a subgular vocal sac, and the throat black.

They lack vocal sacs but all species are known to call.

When it calls, the throat swells, but the vocal sac is not visible.

There is a single vocal sac in the throat.

The head joins the body without a noticeable neck and there is no external vocal sac.

"A male would have this big vocal sac to make his calls."

The male has a pair of vocal sacs which are used during the mating season.

The development of the vocal sac is different in most species, however they mostly follow the same line.

The male has a white or grey vocal sac and the female a pale throat.

Male with two internal vocal sacs, the openings of which are very small.