large, spinose scales and small, keeled scales. Jacky dragons also have spinose scales on the sides of their necks. The tympanum is medium-sized and fairly conspicuous. The average size of a jacky dragon is 9 in (22.86 cm) including the tail, though they have been recorded at lengths up to 17.5 in (44.45 cm). The length of the tail is generally twice as long as that of the body. The average mass of the jacky dragon is 30 g. The largest dragons, however, have been recorded at around 67 g. The size of the dragons' heads can be used to differentiate between sexes, with males usually having conspicuously larger heads. Reproduction and life cycle Gravid females are found from October until February. Females lay up to eight eggs. Clutch size tends to be positively correlated with female body size. Most adult females lay at least one clutch every summer. They tend to lay their clutches under sheets of bark or decaying vegetation over sandy deposits. The first young begin to appear at the end of December and are abundant by February. Jacky dragons are usually about three inches in length immediately following hatching. The sex of the hatchlings is determined by the temperature of the nest, a process known as temperature-dependent sex determination (TSD). The hatchlings are females in low- and high-temperature environments and males in medium-temperature environments. This causes young dragons from clutches laid earlier in the season to be predominately male. Shine suggests, however, that the sex of the hatchling is determined soon after oviposition when the mother still has considerable control over the temperature of the nest. This may falsify the hypothesis that TSD evolved in lizards so as to match the sex of the offspring with environmental conditions that may be unpredictable when the clutch is laid, as is most likely the case for turtles, tuataras, and crocodiles. In fact, recent research suggests TSD has evolved in lizards so as to ensure reproductive success in the offspring. The jacky dragon reaches sexual maturity rapidly. Females can lay clutches within one year of hatching. The average lifespan of the jacky dragon is four years, which is significantly shorter than most lizards. Ecology Distribution Jacky dragons are found along the southeastern coast of Australia. They have been found as far north as central Queensland, in New South Wales, Victoria, and in the southeastern portion of South Australia. Habitat