Draco (lizard)

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Draco is a genus of agamid lizards<ref name=RDB/> 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 Template:Convert have been recorded, over which the animal loses only Template:Convert in height which makes for a glide ratio of 6:1. This is done by a lizard of only around Template:Convert in total length, tail included.<ref name=ross>Piper, Ross (2007). 'Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals'. Santa Barbara, California: Greenwood Press{{ safesubst:#invoke:Unsubst||date=__DATE__ |$B= Template:Fix }}.</ref> They are found across Southeast Asia and Southern India and are fairly common in forests, areca gardens, teak plantations and shrub jungle.

History of discoveryEdit

File:Flying Dragon Mivart.png

Skeleton of Draco

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 dragons of mythology. 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.<ref name=":0" />

DistributionEdit

Species of Draco are widely distributed in the forests of Southeast Asia, with one species, Draco dussumieri, inhabiting Southern India.<ref>Template:Cite journal</ref>

Habitat and ecologyEdit

Members of Draco are primarily arboreal, inhabiting tropical rainforests, and are almost never found on the forest floor.<ref name=":0" /> They are insectivorous, primarily feeding on eusocial insects such as ants and termites.<ref>Template:Cite journal</ref> The colour of the patagium is strongly correlated to the colour of falling leaves in their range, which complements their cryptic camouflage resembling tree bark; both are likely to be camouflage against predatory birds.<ref>Template:Cite journal</ref>

GlidingEdit

File:Draco takeoff.gif

Takeoff and initial stages of gliding, slowed down 10x, showing the attachment of the forelimbs to the gliding membrane

File:Draco landing.gif

Landing, slowed down 20x

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.<ref>Template:Cite journal</ref> The hindlimbs in cross section form a streamlined and contoured airfoil, and are also probably involved in generating lift.<ref name=":0" /> Gliding is both used to escape predators, and as the primary means of moving through their forest habitat.<ref name=":0">Template:Cite journal</ref> The folding and unfolding of the membrane is controlled by the iliocostalis and intercostal muscles, which 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.<ref name=":2">Template:Cite journal</ref> 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.<ref name=":1">Template:Cite journal</ref>

Life historyEdit

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 brightly-colored dewlap that contrasts with their camouflaged body scalation.<ref name=":0" /> The dewlap is translucent, and deliberately orientated perpendicular to the orientation of the sun during display in order to enhance visibility.<ref>Template:Cite journal</ref> Draco is sexually dimorphic, with females being larger than males.<ref>Template:Cite journal</ref><ref>Template:Cite journal "Similarly, in some Draco it has been suggested that females have larger heads for their body size than males to counterbalance an increased weight burden that is displaced posteriorly during gravidity."</ref> 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 a clutch of 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.<ref name=ross/>

PhylogeneticsEdit

Within Agamidae, Draco is a member of the subfamily Draconinae. Within Draconinae, Draco is most closely related to the genera Japalura and Ptyctolaemus.<ref>Template:Cite journal</ref>

SpeciesEdit

File:Draco lizard display.gif

Male D. dussumieri displaying for females by extending his dewlap, from Dandeli, India

File:Five-lined Flying Dragon (Draco quinquefasciatus) (14136387745).jpg

Size of D. quinquefasciatus in comparison to a human hand, from Sarawak, Malaysia

File:2005-Draco-dussumieri.jpg

Highly camouflaged D. dussumieri from Bandipur National Park, India

The following 41 species are recognized:<ref name=RDB>Template:NRDB genus</ref><ref>"Draco ". Dahms Tierleben. www.dahmstierleben.de.</ref>

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

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

Similar prehistoric reptilesEdit

File:Weigeltisaurus reconstruction.png

Life restoration of the weigeltisaurid Weigeltisaurus jaekeli, one of the oldest known gliding reptiles

Several other lineages of reptile known from the fossil record have convergently evolved similar gliding mechanisms consisting of a patagium or plate flanking the torso; the weigeltisaurids are the oldest of these, living in the Late Permian from around 258 to 252 million years ago. Other lineages include the Triassic kuehneosaurids and Mecistotrachelos, and the Cretaceous lizard Xianglong.<ref name=":0" /><ref name=":2" />

ReferencesEdit

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