Taxonomically, dragons have always been considered an isolated group. According to the Monster Manual, they are all members of the same genus (Draco) and, apparently, only distantly related to the reptiles. However, from faraway Drogasia comes word of a form that is obviously related to the Draconian dragons, but also merits distinction as a separate group.
The Drogasian land dragons, or "landragons," as they are called by the natives, have breath-weapon abilities like their cousins do, but they lack the ability to fly. However, they have stunted wing appendages (often put to use for purposes other than flight) that serve as evidence of the strong evolutionary link between the two groups. Other noteworthy differences between the types include the bulkier build of the Drogasians, the shorter, thicker tail, often used as a defensive weapon, and a different growth pattern from that of all flying dragons. Also, few of these flightless dragons show the intelligence associated with their better-known counterparts.
These differences have led sages to place the three documented species of "landragons" of Drogasia in a separate genus, that being Drogas. Dragons of this genus have the same fear aura ability as their flying cousins, but they never possess any magical ability. All three species have developed strong physical abilities, of both offensive and defensive nature, to offset their lack of flight and magic, and overall they can be at least as formidable as the Draconians.
A land dragon found outside its lair will not be asleep. One (or more) will be asleep whenever encountered inside a lair (usually a cave or an old dungeon), unless the party awakens the dweller(s) of the lair in its approach.