Draco (lizard)

''Draco'' is a genus of agamid lizards that are also known as flying lizards, flying dragons or gliding lizards. These lizards are capable of gliding flight via membranes that may be extended to create wings (patagia), formed by an enlarged set of ribs. They are arboreal insectivores.

While not capable of powered flight they often obtain lift in the course of their gliding flights. Glides as long as have been recorded, over which the animal loses only in height, which is quite some distance, considering that one lizard is only around in total length, tail included. Piper, Ross (2007). 'Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals'. Santa Barbara, California: Greenwood Press. They are found across Southeast Asia and southern India. and are fairly common in forests, areca gardens, teak plantations and shrub jungle.

History of discovery

Carl Linnaeus described the genus in 1758, with the type species being ''Draco volans.'' The name of the genus is from the Latin term for mythological dragons. In the early and mid 20th century, there was controversy about their gliding capabilities, with some authors suggesting that the patagia were solely for display, but research in the late 1950s firmly established the gliding function of the patagia.

Gliding

The lizards are well known for their "display structures" and ability to glide long distances using their wing-like, patagial membranes supported by elongated thoracic ribs to generate lift forces. The hindlimbs in cross section form a streamlined and contoured airfoil, and are also probably involved in generating lift. Gliding is both used to escape predators, and as the primary means of moving through their forest habitat. The folding and unfolding of the membrane is controlled by the iliocostalis and intercostal muscles, that in other lizards are used to control breathing. At takeoff, the lizard jumps and descends headfirst, orientating itself so that the underside of the body is parallel to the ground. During flight, the back arches, forming the patagium into a cambered surface, and the forelimbs grab the front of the patagium, forming a straight front edge to the aerofoil. The forelimbs are used to manipulate the patagium in order to adjust the trajectory during flight. Maximum gliding speeds have been found to be between 5.2 and 7.6 metres per second, depending on the species. During the landing process, the glide is mostly horizontal. Immediately before landing, the forelimbs release the patagium. The landing is forefeet-first, followed by hindfeet. The shape of the gliding membrane does not correlate with body size, meaning the larger species have proportionately less lift-generating surface area and consequently higher wing loading.

Habitat and ecology

Members of ''Draco'' are primarily arboreal, inhabiting tropical rainforests, and are almost never found on the forest floor. They are insectivorous, primarily feeding on ants and termites. The colour of the patagium is strongly correlated to the colour of the local falling leaves, likely as camouflage against predatory birds.

Social behaviour and reproduction

''Draco'' lizards are highly territorial, with the home range consisting of one or a few trees. The trees are actively guarded by males, with territory-less males searching the forest landscape in search of vacant areas. Experimental studies have determined that suitable unoccupied territories were claimed within a few hours of the removal of a dominant male. Females move freely through the territories. The patagium is used as a display structure during courtship and territorial disputes between rival males, alongside the opening of a colourful dewlap. The dewlap is translucent, and deliberately orientated perpendicular to the orientation of the sun during display in order to enhance visibility. ''Draco'' is sexually dimorphic, with females being larger than males. The only time a female flying lizard ventures to the ground is when she is ready to lay her eggs. She descends the tree she is on and makes a nest hole by forcing her head into the soil. She then lays 2–5 eggs before filling the hole and guards the eggs for approximately 24 hours, but then leaves and has nothing more to do with her offspring.

Distribution

Species of ''Draco'' are widely distributed in the forests of Southeast Asia, and one species, ''Draco dussumieri,'' inhabits Southern India.

Phylogenetics

Within Agamidae, ''Draco'' is a member of the subfamily Draconinae. Within Draconinae, ''Draco'' is most closely related to the genera ''Japalura'' and ''Ptyctolaemus.''

Species

The following 40 species are recognized:

* '' Draco abbreviatus'' – Singapore flying dragon
* ''Draco beccarii'' Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). ''The Eponym Dictionary of Reptiles''. Baltimore: Johns Hopkins University Press. xiii + 296 pp. . (''Draco beccarii'', p. 21).
* ''Draco biaro'' – Lazell's flying dragon
* ''Draco bimaculatus'' – two-spotted flying lizard
* '' Draco blanfordii'' – Blanford's flying dragon, Blandford’s flying lizard, Blanford's gliding lizard
* ''Draco boschmai''
* '' Draco caerulhians''
* ''Draco cornutus''
* ''Draco cristatellus'' – crested flying dragon
* ''Draco cyanopterus''
* ''Draco dussumieri'' – Indian flying lizard, Western Ghats flying lizard, southern flying lizard
* ''Draco fimbriatus'' – fringed flying dragon, crested gliding lizard
* ''Draco formosus'' – dusky gliding lizard
* ''Draco guentheri'' – Günther's flying lizard, Guenther's flying lizard
* ''Draco haematopogon'' – red-bearded flying dragon, yellow-bearded gliding lizard
* '' Draco indochinensis'' – Indochinese flying lizard, Indochinese gliding lizard
* ''Draco iskandari''
* ''Draco jareckii''
* ''Draco lineatus'' – lined flying dragon
* ''Draco maculatus'' – spotted flying dragon
* ''Draco maximus'' – great flying dragon, giant gliding lizard
* '' Draco melanopogon'' – black-bearded gliding lizard, black-barbed flying dragon
* '' Draco mindanensis'' – Mindanao flying dragon, Mindanao flying lizard
* '' Draco modiglianii'' – lined flying dragon
* ''Draco norvillii'' – Norvill's flying lizard
* ''Draco obscurus'' – dusky gliding lizard
* ''Draco ornatus'' – white-spotted flying lizard
* ''Draco palawanensis''
* ''Draco quadrasi'' – Quadras's flying lizard
* ''Draco quinquefasciatus'' – five-lined flying dragon, five-banded gliding lizard
* ''Draco reticulatus''
* '' Draco rhytisma''
* ''Draco spilonotus'' – Sulawesi lined gliding lizard
* ''Draco spilopterus'' – Philippine flying dragon
* ''Draco sumatranus'' – common gliding lizard
* ''Draco supriatnai''
* '' Draco taeniopterus'' – Thai flying dragon, barred flying dragon, barred gliding lizard
* ''Draco timoriensis'' – Timor flying dragon
* ''Draco volans'' – common flying dragon
* ''Draco walkeri''

''Nota bene'': a binomial authority in parentheses indicates that the species was originally described in a genus other than ''Draco''.

Prehistoric analogues

Several other lineages of reptile known from the fossil record have convergently evolved similar gliding mechanisms, the oldest of these being the weigeltisaurids, known from the Late Permian, around 258 to 252 million years ago. Other lineages include the Triassic kuehneosaurids and ''Mecistotrachelos,'' and the Cretaceous lizard '' Xianglong''.

See also

* Flying and gliding animals
* ''Chrysopelea'' gliding snake

References

Further reading

* Goin CJ, Goin OB, Zug GR (1978). ''Introduction to Herpetology, Third Edition''. San Francisco: W.H. Freeman & Company. xi + 378 pp. . (Genus ''Draco'', pp. 41, 86, 112, 279, 288).
* 33 pp.
* Linnaeus C (1758). ''Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, diferentiis, synonymis, locis. Tomus I. Editio Decima, Reformata.'' Stockholm: L. Salvius. 824 pp. (Genus ''Draco'', p. 199).
*

{{DEFAULTSORT:Draco (Genus)
Draco
Lizard genera
Gliding animals
Taxa named by Carl Linnaeus