For those of you who don't know, here's an explanation of science fantasy. My idea:

On the planet Hydra-VII, the economy is based around one thing: pit fighting. While humans are common, even more so are the dragons and wyverns. These majestic reptavians are native to the planet, and have been domesticated by humans. The story will revolve around two fighters and their dragons.

Alright, so it's a blend of the Pit Dragon Trilogy, "Dragon Booster", and Bionicle's Bara Magna. I have a few key things for the story:

Dragon- Large, flightless reptilian creatures. Most are carnivorous, and range in size from a Terran horse, up to the size of a Tyrannosaurus. Warm blooded, with a relatively high metabolism. Genetic diversity is so great that hatchling from the same clutch of eggs may look extremely different. Despite how closely related they are, dragons cannot breed with wyverns.
Wyvern- Large reptavians. All are carnivorous, and can grow more than ten feet at the hip (with a 45 foot wingspan), although larger specimens are exceedingly rare. Wyverns are divided into two subtypes: feathered and unfeathered. Feathered wyverns have wings like birds; unfeathered wyverns possess wings more similar to Terran bats or pterosaurs.
Sand lizard- Small, cold- blooded reptiles that fill diverse ecological niches. Some have been domesticated by humans as pets.
Crowdrake- Essentially small wyverns, crowdrakes are mostly scavengers. Although not as intelligent as their larger cousins, they have the ability to mimic human speech.
Scale- The currency of Hydra-VII, these are small, gold disks, quite similar in appearance to dragon scales.

If interested, please send a PM!