Species

Elf- Elves are naturally lean and fast, tending to bond with their dragons within a week or two.
Human- Humans vary in size, tending to bond with their dragons after half a month to a month.
Halfbreeds- Halfbreeds are naturally muscular and what they lack in speed, they gain in strength.  They tend to bond with their dragons after a month and a half.

Dragon Types

Fire- Fire dragons aren't quite muscular, not quite lean.  They're often yellow, red, and orange, and breathe flames.
Water- Water dragons are more lean, often varying between green, blue, and purple.  They breathe water, the temperature on a scale of freezing to boiling.
Ice- Ice dragons aren't quite muscular, not quite lean.  They're often pale blue and white, and breathe ice.
Earth- Earth dragons are more muscular, often red/brown, brown, green, and pale yellow.
Sand- Sand dragons are quite lean, often gold, yellow, and white.
Pocket- Pocket dragons are small and lean, can be any colour, and breathe flames.