Common Flying Dragon (Draco volans)

Adult Size: Approximately 19 cm to 22 cm long (7.5 in to 8.5 in) [1]
Points of Interest: Lizard that glides from tree to tree

Draco Volans

Illustration 1. Draco volans Skeleton Diagram. © Kylie 'drago' McCormick.

The Common Flying Dragon of Southeast Asia is an important member of the lizard family. While some lizards have adapted gliding skills, the members of the genus Draco have a special take on gliding. In this instance, reference will be made specifically to Draco Volans, as illustrated above.

Draco volans has adapted its ribs between the fore limbs and the hind limbs to be long and slender, except for the first so-called true ribs that connect to the sternum. These specialized ribs enable a flap of skin, called the patagium, to be used for gliding.

The common flying dragon uses the muscles associated with these ribs only to expand and to fold up the membrane used for gliding. [5] They use their tails to help steer through the air as they glide from branch to branch. [7] They do not keep their patagium spread at all times; they can spread it outward from the body as needed for gliding, but also can fold up the delicate membrane. [6]

Despite their diminutive size, their unique adaptation for gliding is an important consideration for many flying or swimming dragons, which could use elongated ribs along their tails as anatomical rudders in flight or for swimming.

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Anurans (Frogs and Toads)

Size Range: From less than 1 cm (approximately 0.4 in) long to over 30 cm (12 in) [3]
Points of Interest: Limb adaptation, Leaping, Eyes and Eyesight, and Toxins

Frog Skeleton

Illustration 2. Anuran Skeleton Diagram. © Kylie 'drago' McCormick.

Terminology can prove to be an issue here, since the term "frog" is sometimes used to describe all tailless amphibians, despite being a more appropriate term for the species of the family Ranidae, so-called "true frogs." [2] The term "Anuran" also applies to tailless amphibians, or frogs and toads. The distinctions between frogs and toads is not helpful scientifically, since the terms "toad" and "frog" arose to describe similar species without understanding their true biological relation to one another. For this reason, the term "anuran" will be used. [8]

Anurans share a simple design that has been adapted in habitats all over the world. The general anuran has only a few vertebrae (between five and ten). [9] The latter bones of the front limbs and hind limbs have been fused, stressing their leaping ability for speed. [9] As in Illustration 2, the fore limb has a radioulna instead of the two separate bones of radius and ulna, as found in other vertebrates. Similarly, the hind limb has a tibiofibula instead of the tibia and fibula found in other vertebrates.

The shortness of the anuran vertebral column has caused other adaptations. Since most anurans have no neck, they have to move their entire bodies to look in a new direction. For this reason, frogs have huge, protruding eyes that provide almost 360° vision. [9] Anurans also have very sharp eyesight as both a precaution to detect predators and an aid in hunting to guide their tongues to their prey. [9]

Anurans are ectotherms, or animals that obtain their body heat from external sources in order to maintain their body temperature. [10] The term "cold blooded" is commonly used to describe ectotherms, but this is a complete misnomer, [10] since an ectotherms' body temperature can be maintained by obtaining heat from other sources or hiding from the sun on days, or in areas, where the heat would be too much for the animal. Also, the term "cold blooded has become pejorative, for it has been used to imply a vicious nature of cruelty. [11]

The largest anuran species living in the world is the Conraua goliatha, or the Goliath Frog, which lives in parts of Africa. This anuran can grow up to 30 cm (12 in) and weigh in at 3 kg (6.6 lbs). [3] The smallest anuran living today is the Tiny Gold Frog (Psyllophryne didactyla) found in Brazil, averaging a size of less than 1 cm (0.4 in) long. [3]

Toads, specifically so-called true toads from the family Bufonidae, are also important to consider here. [13] Many toads are terrestrial, [12] and they are characterized by their warty epidermis. [13] They generally have squat, heavy bodies with tough, leathery skin. [14]

Most toads contain powerful toxins within their warts and glands on their backs, causing reactions from an unpleasant taste to death in predators, depending on the species. [15] Unlike the venom in snakes, however, the toxins found in the skins of anurans, frogs and toads alike, is used for defense alone, not for subduing prey. [16] Some species even advertise their toxicity, like the Poison Dart Frogs, which present bright, enamel-like colors to warn predators of their dangerous skin and prevent attacks all together. [15]

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Footnotes

  1. Whitfield 428
  2. Parsons ix
  3. Parsons 26
  4. Crocodilian Biology Database: Locomotion (gallop)
  5. Owen 265
  6. Zabludoff 42
  7. Zabludoff 43
  8. Parsons 2
  9. Parsons 6
  10. Parsons 9
  11. Parsons 10
  12. Parsons 13
  13. Parsons 19
  14. Parsons 21
  15. Parsons 70
  16. Parsons 73

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

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