Dragon Anatomy and Physiology

Avian Anatomy

• Avian Classification and Number of Species
• General Description of Size
• Survey of Avian Biology
• Avian Skeleton
• Considerations on Dragon Anatomy and Physiology
• Footnotes

Diagram 1. The scientific classification of birds.

Birds are part of the Animalia Kingdom and the Chordata phylum, which refers to vertebrates and a few closely related invertebrate species. The class Aves has two superorders with twenty-nine orders. Across these orders, there are 10,000 species and 22,000 subspecies.²

There are many highly-adapted avian species across the world. Some, like the Arctic Skua (Stercorarius parasiticus), live in the harsh climates of the polar regions, spanning from Alaska to Siberia and as far south as Scotland; some live off the southern coasts of Australia, South America, and southern Africa.³ Other avian species, like the Torrent Duck (Merganetta armata), have webbed feet to hunt in water and live on land, as all the members of the Anatidae family, including ducks, geese, and swans.⁴

While avian species are well-known for their ability to fly, there are many flightless birds, including members of the order Sphenisciformes, which includes species like the Rockhopper Penguin (Eudyptes chrysocome) that have adapted their physiology to have fore flippers instead of flight-capable wings.⁷ Other flightless species, including the Ostrich (Struthio camelus), are believed to have evolve feathers for insulation but not for flight.

Flying birds have a wide range of wing structure, generally adapted in relation to their flight patterns. Aerial performance has some standard measurements that indicate maneuverability and speed.⁸ Two parameters include aspect ratio⁸ and wing loading.⁹

Aspect ratio is defined as the total wingspan of the bird, including the shoulder width, divided by the wing breadth.⁹ Birds with high aspect ratios generally have patterns of long distance, soaring flight with few flaps, such as the albatross.⁸ Birds with short, tapered wings have low aspect ratios, requiring more flapping but also provided much more maneuverability, such as the falcon.⁸

Wing Loading is another standard measurement, examining the property of lift given a certain wing design. It is calculated as the ratio of the animal's body weight versus the surface area of the wing.⁹ Wing Loading is also used to assess the capability of a gliding animal's movement through the air.⁹

Avian anatomy varies with the adaptation of the forelimb, such as flippers for swimming and wings for flying. Flying birds have additional adaptations, such as lighter bones and, in some instances like the hummingbird, fewer organs, in order to maximize flight capabilities.

Illustration 1. General Avian Anatomy. © Kylie 'drago' McCormick.

Birds have a special adaptation for flight, called the furcula, sometimes call the wishbone in culture and culinary tradition, which helps protect the animal's thorax during flight. Other specific bone structures of interest include the number of fused bones in the skeleton, such as the tibiotarsus and hypotarsus (or tarsometatarsus) in the hind legs and feet. The pygostyle is a series of fused caudal vertebrae that serve as supports for the tail feathers of the bird.

The fusion of multiple bones for the specialization of flight is interesting for comparative anatomy, especially when attempting to identify possible configurations for flight-capable dragon anatomy.

However, one of the most important aspects of bird anatomy to dragon anatomy is the sizes of flight-capable birds. Since the wandering albatross has the largest avian wingspan, with a maximum size of 3.63 m (11 ft 11 in),¹ it is likely that dragon anatomy based upon bird anatomy would have a similar limit in size.

1. Bird 70
2. Avibase - The World Bird Database
3. Spilling 203
4. Spilling 21
5. Raptor Information Network: Family Names
6. Strigiformes Order: Owl Families
7. Spilling 468
8. Shipman 249
9. Shipman 186
10. Bird 7

For more information on footnotes and references, please see the Bibliography.