Western Dragons: Descriptive Overview
Western Dragons possess both four legs and wings, which makes it difficult to identify them in the animal kingdom, especially among the vertebrates, which remain exclusively tetrapods. All species known to science that have solved the solution to the Flight Problem have been vertebrates as well.
Descriptions of Western dragons vary greatly, from depictions of Saint George and the dragon with the monster being smaller than a horse, to descriptions of dragons being a dozen feet (3.65 m) long to fifty feet (15.24 m) long.
Common traits of Western Dragons include the following:
- Reptilian appearance
- Wings and/or the Ability to Fly
- Tremendous Strength and/or Powerful Muscles
- Heavy Bodies, Terrible Jaws and Teeth
- Noxious Breath and/or the ability to spew water, fire, or venom
- Dangerous, even poisonous, blood
Some less than common traits of Western Dragons, yet still applicable in consideration, include the following:
- Association with a protected area, especially mountains or rocky regions or even bodies of water
- Fabulous Eyes
- Association with dangerous geography, such as volcanoes
Body Shape and Size
Many modern artists model western dragons off of mammals, such as felines, with additional wing appendages. While this representation can be a type of Western dragon, the model of a feline, or other similar mammals, leaves behind an important part of Western dragon description: reptilian appearance.
Reptiles, especially lizards, have low-slung bodies. Crocodiles are excellent examples of this, as are Komodo Dragons. Crocodiles do possess the ability to hoist themselves off the ground, and some can even gallop, but for the most part, they keep their bellies on the ground and move with them dragging on the ground, too. Felines, on the other hand, keep their core above the ground except when lying down. This is due to slight difference in the arrangement in the limb bones, despite the animals in question having very similar anatomy of the limbs, except that felines and other mammals have a patella, or kneecap.
Western dragons of enormous size would not necessarily need to have been particularly tall, as a large crocodile might remain low to the ground but still be up to twenty-five feet long. For this reason, Western dragon anatomy will be considered in terms of reptiles, especially Komodo Dragons and Crocodiles, with low-slung bodies and the rough shape of the hind limbs, including the lack of a kneecap.
The largest known crocodile species is the Estuarine Crocodile or the Saltwater Crocodile (Crocodylus parosus), with the average size of males being roughly 19 feet (5.8 m).  However, some individuals in the wild have been known to grow to a length of 22.5 ft (7 m) and weigh up to 2,205 lbs. (1,000 kg).  The largest known lizard is the Komodo Dragon (Varanus komodensis), which can grow to the size of 10 ft (3 m) and weigh up to 360 lbs (163.3 kg). 
Solving the Problem of Flight
Western Dragons are generally depicted with bat-style wings in art, but this does not mean that other wing formations would not be worth considering. Bats as considered denizens of the dark, living in caves and associated with the darker side of the world, such as their association with vampires. This may be the reason bat-style wings have been associated with dragons.
Bats are slower fliers than birds, but they have far more maneuverability than birds.  Often when discussing flight, the issue of aerodynamics and size come into play. Few birds are very large, and even those that are aren't the enormous monsters described in myth. Birds and bats also tend to be light in order to fly.
However, the third known model of flight resides in the pterosaur. Since they evolved flight much earlier than birds or bats, there was more time to develop a diverse range of wingspans and types. This same diversity can be seen in birds, which range from the hummingbird to the albatross.
The larges pterosaur currently known is the Quetzalcoatlus northropi, which had a wingspan of 39 ft (12 m) and weighed in at a hefty 280 lbs. (137 kg). 
Finally, many dragons are mentioned as winged without specific reference to flight. It may seem ridiculous for an animal to have wings without the ability to fly, but many novel structures in species can prove to be difficult to explain. For example, the giraffe's long neck has baffled many scientists for years.  Many people go immediately to the conclusion that giraffes have long necks for the sake of feeding on hard-to-reach vegetation, but in reality giraffes generally feed at shoulder-length height and their shape and size make drinking water quite difficult; they have to splay their legs to eat grass or drink water.  New research shows that a giraffe's long neck and legs have many different purposes, from the ability to see long distances as a defense mechanism to a special social hierarchy determination.  Giraffes are a social species with a hierarchy, and males will fight for dominance by using their long necks. 
In short, some novel or extraordinary adaptations of species may defy so-called 'obvious' reasons for their existence. Unfortunately, the known living models of animals with wings that cannot fly are flightless birds, many of which are believed to be transitional species toward flight. On the other hand, penguins are flightless birds that have highly successful marine locomotion due to their wings, which are flat, un-foldable paddles that propel them through the water, enabling them to swim underwater to catch food.  Therefore, a Western dragon's wings may have been a form of adaptation to marine life as opposed to an evolution in flight.
Noxious Breath and Blood
Many dragons are associated with noxious smells or breath, and in myth the blood of a slain dragon corrupts the ground onto which it falls. Sometimes the scent or breath of a Western dragon is compared to that of fire or poison.
Perhaps fire-breathing dragons are symbolic or exaggerations of a caustic scent. Most snakes have musk glands near the base of their tails, used for a number of inter-species communications, such as marking territory, but these can also be used for defense by offending a predator and enabling the snake to escape. 
While it may seem unlikely that a snake's musk could offend people to the point of comparing it to fire, consider the impact of cutting an onion. When cutting an onion, enzymes are freed, mixing to create propanethiol S-oxide, a volatile sulfur that 'burns' the eyes and commonly causes tears to form.  The tears wash away the irritant from the eyes, but continued exposure to the released chemicals can cause continued and more painful discomfort. And that's a common reaction to a vegetable that lacks fangs!
Another possibility can be found in the spitting cobra, which can eject venom not only through their fangs but also into the air. The few snake species known to spit venom have special modifications of the fangs, causing venom to be ejected from the glands into the air at a high speed and in the form of a fine mist.  These snakes have been known to spit venom for several meters with reasonable accuracy, and the snake raises its head before spitting venom, almost ensuring the victim will receive some venom to the eyes.  Immediate pain results, and in humans, temporary or even permanent blindness can result, especially in untreated cases. 
While actual flame would be an extremely novel development, not to mention dangerous for the animal itself, there are many offensive and defensive mechanisms that Western dragons could have possessed that associated them with 'fire breath.' Depending on the chemical compounds in the dragon's saliva and other bodily secretions, it is possible that the musk of a dragon could combine to create a particular acid that could cause pain to mammalian eyes, much like the onion. Venom spitting is a rare ability even among poisonous snakes, and it manifests itself as a spray-like weapon commonly used as defense. This could also be the source of a dragon's 'fire breath.'
In tales where the dragon's blood is considered noxious, it is very likely that the situation is much like the onion-cutting. Enzymes in the blood suddenly touch with the air, possibly combining with new chemicals and causing a volatile gas to be released. If this were a possible development, a Western dragon might also possess a defense mechanism known as autohaemorrhagy, which some snakes and lizards use. Autohaemorrhagy is the voluntary rupture of small blood vessels, causing blood to ooze out at various parts of the body. 
Tetrapod Western Dragon
The Western Dragon is known for having six limbs: four legs and two wings, generally putting it outside the realm of tetrapod. In Illustration 1, the skeleton of a tetrapod has evolved to have the appearance of six limbs.
Illustration 1. Tetrapod Western Dragon Skeleton. © Kylie 'drago' McCormick. Enlarged Version
The humerus attaches at the radius and ulna, but in this instance the joint allows the radius to be a fore limb while the ulna has adapted a flying structure. In this case, the wing of a bat, although the possibility of a more avian wing or pterodactyl wing could also be used, as well as another independent solution to the flight problem. The wing could be folded upwards when the dragon is on all fours, and the shortest metacarpals would be able to tuck behind the modified rib at the neck. Along the tail, elongated ribs form a tail rudder, much like the ribs in the gliding lizard Draco volans.
This hypothetical dragon skeleton would be able to fly, but its locomotion would not necessarily be impressive on the ground. Of course, neither is the crocodile, but that does not mean that it is not a formidable foe.
Illustration 2. Tetrapod Western Dragon. © Kylie 'drago' McCormick. Enlarged Version
The Western dragon with hypothetical skeletal structure as in Illustration 1. This illustration has semi-translucent wings to better display the underside of the dragon.
- Shedd 65
- Whitfield 469
- Estuarine Crocodile
- Shipman 238
- Whitfield 448
- The Giraffe's Short Neck
- What Good Is That Long Neck? Link defunct: <http://www.highlightskids.com/Science/Stories/SS0395_whatgoodislongneck.asp>
- Whitfield 298
- Mattison 136
- Mattison 137
- Why do onions make you cry?
For more information on footnotes and references, please see the bibliography.