Komodo dragon (Varanus komodoensis)

If you think of dragons as supersize reptiles with a nasty bite, the Komodo dragon is the real deal. Up to 3m long and weighing as much as 70kg, they are the world's biggest lizards.

They can't breathe fire, but they kill pigs, deer and water buffalo with their mouths. In the past it was assumed that bacteria in their saliva caused blood poisoning. But in 2009 scientists discovered that Komodo dragons have venomous saliva that floods the wounds inflicted by their razor-sharp teeth.

The tale of how the dragons earned their nickname is suitably legendary. In 1926, W. Douglas Burden, grandson of a wealthy railway magnate, set off to the Lower Sunda Islands of Indonesia to capture a dozen giant lizards for the American Museum of Natural History.

In his memoir of the expedition, Dragon Lizards of Komodo, Burden describes one animal as "a hoary customer, black as dead lava, whose very aspect spoke of indefinite existence". He also details his wife's damsel-in-distress moment, when she was rescued from a dragon by the gun of a fellow explorer. The adventure immortalised the Komodo dragon, and inspired the film King Kong.

Dragonsnake (Xenodermus javanicus)

The dragonsnake is native to Indonesia and Malaysia, and sometimes turns up in Thailand and Myanmar. It is a mysterious species that goes by several names, including Javan mudsnake, Javan tubercle snake and rough-backed litter snake.

Its mythical name was inspired by its characteristic scales. Xenodermus means 'strange skin', and refers to the rows of knobbly black scales that run in raised ridges down the snake's body. Dragonsnakes commonly measure 60cm (2 feet), with females slightly larger than males.

There is only one species of dragonsnake. In 2013, a genetic analysis suggested they are a sister group to the primitive, aquatic file snakes of Australia and Indonesia.

Despite being discovered way back in 1836 and hunting on rice paddies, not much is known about dragonsnakes. They mostly hunt at night, for frogs.

Bearded dragons (Pogona sp.)

Bearded dragons are a favourite with pet owners around the world. The eight species in the Pogona genus all come from central Australia.

These dragons puff out their throats to create an imposing ruff of spiked scales. This 'beard' also turns black during courtship, aggression and times of stress.

In 2014 it emerged that the central bearded dragon actually changes its shade in sync with its circadian rhythms. It starts the day dark and becomes progressively lighter, appearing cream at night. The colour change may help it absorb heat during the day and stay warm through cold nights.

The central bearded dragon has also surprised scientists with its ability to learn. In 2015 Anna Wilkinson of the University of Lincoln in the UK and her colleagues found that the lizards could imitate a fellow dragon to complete a task – pushing a door open in a particular direction.

Shocking pink dragon millipede (Desmoxytes purpurosea)

At the smaller end of the real dragon scale we have the millipedes. Dragon millipedes are found throughout South East Asia and named for the elaborate spikey protrusions, or 'paranota', that are thought to shield their many legs.

One of the most striking species was discovered in 2007 in Thailand, living in a limestone cavern. Researchers came across the shocking pink dragon millipede sitting in the leaf litter. At 3cm long, it is one of the largest dragon millipedes.

This millipede smells of almonds. That may not sound like an off-putting scent, but it is a signature of poison. Like many other Polydesmida millipedes, the shocking pink dragon millipede produces hydrogen cyanide from its defensive glands. Its bright pink shade warns predators that it is toxic.

More species of dragon millipede have since been discovered in Laos, the Philippines and southern China.

Flying dragon (Draco sp.)

For purists that believe dragons should fly, meet the Draco genus of lizards. They are true gliding reptiles, an adaptation that serves them well in the tropical forests of South East Asia.

Much like aircraft wings are built of struts with a membrane stretched across, these flying dragons have elongated ribs that support a flap of skin, called the patagia. This allows them to glide an average of 8m as they jump between trees. Their slender tails act as rudders for steering.

Thanks to specialised muscles, the dragons can deploy their wings at will, or fold them against their body when not in use.

The lizards are a mottled brown colour for camouflage, but their wings are often brightly decorated. A courting male will extend his bright wings and the flap on his throat to make himself appear bigger.

Giant petaltail dragonfly (Petalura ingentissima)

Dragonflies are found on every continent except Antarctica, with around 5000 species globally. The bulkiest such insect is the giant petaltail, found in Queensland, Australia.

These black-and-yellow striped dragonflies live alongside rainforest streams, their 12cm-long bodies held aloft by wings that span 16 cm. Petaltails are thought to be the most ancient of dragonflies, with a fossil record dating back to the Jurassic.

Experts on western folklore have suggested that dragonflies were named for their dizzying aerial acrobatics, which were thought by Europeans in the Middle Ages to be the devil's work. Dragons and the devil were synonymous at this time. The slender insects were viewed with considerable suspicion: they were falsely accused of biting horses and even of sewing up the eyes and mouths of sleeping children.

Dragonfly larvae do have a fearsome reputation as voracious predators, using their highly modified mouth parts as a hydraulic grabber to lunge at prey. Most petaltail larvae develop in burrows beside rivers, where they wait for passing prey.

Dragonets (Callionymidae)

Tales of dragons aren't restricted to the land and air. In Asian mythology dragons are often associated with water, and there are many sea animals that are named accordingly.

Some of the most attractive are dragonets, tropical fish found in the Indo-Pacific. These "little dragons" are named for their large dorsal fins, which can resemble spectacular articulated wings in species such as the Japanese dragonet and Seychelles dragonet.

Dragonets are found close to the sea bed, and many sport sandy colours to disguise themselves from predators. However, the mandarinfish flaunts a psychedelic mix of electric blue and fierce orange to blend in with its colourful coral reef home in the Pacific. In 2013 scientists found that mandarinfish have unique pigment cells that can glow either blue or red.

To protect itself from predators, the mandarinfish secretes a toxin in the thick mucus that covers its body. This slimy mucus is common among dragonets, and has an unpleasant smell and taste. This could explain the name Australians have given some of their local species: stinkfish.

Black dragonfish (Idiacanthus atlanticus)

The black dragonfish looks like the grimmest of fairy-tale villains, with a long, black body and terrifying, fang-like teeth.

It is a deep-sea fish, living as much as 2000m below the surface of the Atlantic Ocean, and is uniquely adapted to the darkness, cold and extreme pressure found at such depths.

It eats marine invertebrates and fish. To lure them, the female dragonfish has a barbel: a thread-like organ that dangles from her chin, with a luminescent blue tip. Adult fish can be 48cm long, with oversized jaws that allow them to swallow huge prey items.

They also have light-emitting organs called photophores scattered across their heads and bodies. These help the fish to find prey, communicate and hide from larger predators.

All this is true of female black dragonfish, but not of males. They are just 5cm long, dark brown and toothless with no functioning gut. Fishermen encounter females when they swim upwards at night to hunt, but males remain in the deep.

Blue dragon nudibranch (Glaucus atlanticus)

The blue dragon nudibranch is a kind of sea slug. Specimens have been found washed up on the shores of Australia, Africa and the south-east US, and recently they have been appearing along the eastern coast of India.

Rather than flying, this marine dragon floats on its back wherever the wind takes it. It travels on the surface tension of the water, using a bubble of air in its stomach for buoyancy. It evades predators by appearing silver to fish below and blue to birds above.

Up to 84 finger-like 'cerata' grow out from the sea slug's body in feathery, wing-like projections. They have earned comparisons with angels and swallows, but these wings are more aptly linked to ferocious dragons. They contain weapons taken from the sea slug's prey – the infamous Portugese Man o'War.

This creature's tentacles contain stinging cells that paralyse fish and deliver searing pain to unwary swimmers. The blue dragon eats the tentacles, and transfers the stinging cells to specialised pouches for its own defence. It may only grow to 3cm long, but it can punch far above its weight.

Seadragons (various species in the Syngnathidae family)

Don't be fooled, seadragons are fish. They are related to seahorses, but rather more flamboyant. The newest species to science is the ruby seadragon, which was discovered in early 2015.

Scientists were already familiar with leafy and weedy seadragons. Both are named for fleshy appendages that mimic sea weeds, to disguise them from predators, and are only found off southern Australia.

Josefin Stiller of the Scripps Institute of Oceanography in La Jolla, California and her colleagues took tissue samples from seadragons from this area, and found they weren't quite as expected. Eventually they found that the specimens they were studying had subtly different skeletons, suggesting they belonged to a new species.

The ruby seadragon was named for its bright red colour. It may live at lower depths, where red-orange light is rapidly absorbed, making its colour an effective camouflage.

Stiller's team has since examined the records of the Western Australia Museum, and found another specimen that washed up on a Perth beach almost a century ago. The story suggests there are more dragon species to be discovered.