The thorny devil grows up to 20 cm (7.9 in) long and can live for 15 to 20 years. The females are larger than the males. Most of these lizards are colored in camouflaging shades of desert browns and tans. These colors change from pale colors during warm weather and to darker colors during cold weather. These animals are covered entirely with conical spines that are mostly uncalcified (not bony).