The genus Pogona is in the subfamily Amphibolurinae of the lizard family Agamidae. Characteristics include broad, triangular heads and flattened bodies with spiny scales arranged in rows and clusters. These are found on the throat, which can be expanded when threatened, and at the back of the head. These scales are used to scare off predators, yet they are not very sharp. Bearded dragons display a hand-waving gesture to show submission (most often when acknowledging another bearded dragon’s territory), and a head-bobbing display to show dominance between dragons. Some have the ability to slightly change colour during rivalry challenges between males, in response to ambient temperature changes such as turning black to absorb heat, and other stimuli. Males grow up to 60 cm (24 in) long, and females up to 51 cm (20 in). Bearded dragons also produce a mild venom originating from primitive venom glands. Although generally harmless towards humans, it is effective towards smaller-sized animals.