The frilled lizard (Chlamydosaurus kingii), also known commonly as the frilled agama, frillneck lizard, frill-necked lizard or frilled dragon, is a species of lizard in the family Agamidae. The species is native to northern Australia and southern New Guinea and is the only member of the genus Chlamydosaurus. Its common names refer to the large frill around its neck, which usually stays folded against the lizard's body. The frilled lizard grows to from head to tail tip and can weigh . Males are larger and more robust than females. The lizard's body is generally grey, brown, orangish-brown, or black in colour. The frills have red, orange, yellow, or white colours.
The frilled lizard is largely arboreal, spending most of its time in trees. Its diet consists mainly of insects and other invertebrates. It is more active during the wet season, when it spends more time near or on the ground, and is less observed during the dry season, during which it seeks shade in the branches of the upper canopy. It breeds in the late dry season and early wet season. The lizard uses its frill to scare off predators and display to other individuals. The species is considered to be of least concern by the International Union for Conservation of Nature.
Taxonomy
British zoologist John Edward Gray described the frilled lizard in 1825 as Clamydosaurus kingii. He used a specimen collected by botanist Allan Cunningham at Careening Bay, off north-western Australia, while part of an expedition conducted by Captain Phillip Parker King in . The generic name, Chlamydosaurus, is derived from the Ancient Greek chlamydo (χλαμύς), meaning "cloaked" or "mantled", and Latin saurus (sauros), meaning "lizard". The specific name, kingii, is a Latinised form of King. It is the only species classified in its genus. A 2017 mitochondrial DNA analysis of the species across its range revealed three lineages demarcated by the Ord River and the southeast corner of the Gulf of Carpentaria (Carpentarian Gap). One lineage ranged across Queensland and southern New Guinea and is sister to one that ranged from western Queensland to the Ord River. The ancestor of these two split from a lineage that populates the Kimberley. Frilled lizards entered southern New Guinea possibly around 17,000 years ago during a glacial cycle, when sea levels were lower and a land bridge connected the island to Cape York. The study upholds C. kingii as one species with the different populations being "shallow allopatric clades".
The following cladogram is based on Pyron and colleagues (2013).
Description
thumb|left|Anatomy of the frill of Chlamydosaurus kingii
The frilled lizard can reach a total length of around and a head-body length of , and weighs at least . It has a particularly large and wide head; a long neck to accommodate the frill; long legs and a tail that makes most of its total length. The species is sexually dimorphic, males being larger than females The corners of the frilled lizard's eyes are pointed and the rounded nostrils face away from each other and angle downward. Most of the lizard's scales are keeled, having a ridge down the centre. From the backbone to the sides, the scales alternate between small and large. The frill is laterally symmetrical; the right and left sides are attached at the bottom in a V-shape, and cartilage-like connective tissue (Grey's cartilage) connects the top ends to each side of the head near the ear openings. The frill is supported by rod-like hyoid bones, and is spread out by movements of these bones, the lower jaw and Grey's cartilage. There is no evidence for other suggested functions, such as food storage, gliding or temperature regulation.
thumb|right|A frilled lizard in a reptile display (frill folded)
Frilled lizards vary between grey, brown, orangish-brown, and black dorsally, the underside being paler white or yellow. Males have a dark belly but a lighter chest. The underside and lateral sides of the species are sprinkled with dark brown markings that merge to create bands on the tail.
Distribution and habitat
The frilled lizard inhabits northern Australia and southern New Guinea. Its Australian range stretches from the Kimberley region of Western Australia east through the Top End of the Northern Territory to Queensland's Cape York Peninsula and nearby islands of Muralug, Badu, and Moa, and south to Brisbane. Frilled lizards also prefer areas with less vegetation on the ground, as they can then better spot prey from above. Male lizards assert their boundaries with frill displays.
These lizards are more active during the wet season, when they select smaller trees and are more commonly seen near the ground; during the dry season, they use larger trees and are found at greater heights. Frilled lizards do not enter torpidity during the dry season, but they can greatly reduce their energy usage and metabolic rate in response to less food and water. Body temperatures can approach . When it gets hotter during day, they climb higher in the canopy for shade.
thumb|left|Frilled lizard in threat display
Frilled lizards primarily feed on insects and other invertebrates, and very rarely take vertebrates. Prominent prey includes termites, ants and centipedes; termites are particularly important food during the dry season, and moth larvae become important during the wet season. There is at least one record of an individual dying of cryptosporidiosis.
Frilled lizards can breed during the late dry and early wet seasons. They can lay multiple clutches per season, and the number of eggs in a clutch can vary from four to over 20. The incubation period can last two to four months, Juvenile males also disperse further from their hatching area. The species reaches sexual maturity within two years; males live up to six years compared to four years for females. Being difficult to breed in captivity, many presumed captive bred lizards are likely to have been taken from the wild. Frilled lizards may also be threatened by feral cats,
Relationship with humans
right|thumb|Frilled lizard from Narrative of a Survey Volume 2, by [[Phillip Parker King, 1827]]
The frilled lizard is considered to be among the most iconic Australian animals along with the kangaroo and koala. In the late 19th century, William Saville-Kent brought a live lizard to England where it was observed by fellow biologists. Another specimen was kept at a reptile display in Paris, as reptiles were becoming more popular in captivity. The species has been featured on some Australian coins.