Dragons

Dragons are a quadrupedal species of giant, warm-blooded reptiles capable of bipedal movement when young and semi-bipedal movement when fully grown. Their homeland is unknown, however they migrate every year and nest in a south-western area of Equestria known as the Dragon Lair. Dragons are capable of flight, and some races of dragons grow horns. This makes them able to directly control magical energy. All dragons, regardless of race, are able to breathe fire from birth. They are notoriously greedy, and in fact their biological growth is accelerated exponentially when they succumb to their innate desire to horde treasure.

Physiology
When young, dragons tend to walk on their hind legs using bipedal locomotion. When grown, their weight and size makes them unable to walk on two legs, rendering them quadrupedal. However, they are able to sit on their haunches and use their front legs so long as they don't need to move from their current position.

Baby dragons are unable to fly, as their wings do not grow in until they reach adolescence. Some races of dragons grow horns, and are theoretically capable of learning how to control magic. All dragons are capable of breathing fire, as it is their specie's unique magic.

Races
Note: Due to the lack of social development amongst dragons, few know how to use magic. Thus renders the differences between the two known races purely cosmetic.

Horned Dragons
Dragons who grow horns, and are thus able to use magic. They are not native to Equestria, however they often find their way there during the Great Dragon Migration or due to their frequent wandering.

Hornless Dragons
Dragons who do not grow horns, and thus are not able to directly use magic. They are the most common race of dragon found in Equestria.

Magic
Dragons are unable to directly manipulate magic unless they grow horns. However, all dragons are able to use their specie's unique magic, fire-breathing.

Unique Magic: Fire-Breathing
One of the only spells that most dragons ever cast in their lifetime is fire breathing. It is their unique magic, and thus all dragons are able to cast it from birth - though the dragon-fire of young dragons isn't very potent. Dragons use their fire for many things, including combat and the magical transference of items.

Technology
While certain legends do suggest that dragons once had an impressive grasp of technology, they have since lost this knowledge and have degraded into a base animalistic mentality and tribal society.