The Mastadge (or Mastidge) was a beast of burden found on Abydos. They are large, hairy quadrupeds with a long neck, larger than a horse, with a considerably keen sense of smell. Though the origins of the Mastadge are unclear, these creatures may be related to Terran horses who adapted in the harsh heat of day and cold of night in the Abydos desert. They were apparently well suited to living on the harsh desert climate, and also appeared to be able to breathe during sandstorms.
The Mastadge has been domesticated for the Abydonians and, among being used for food and clothing, aided in labor during the thousands of years the population was oppressed by Ra. It is capable of galloping at great speeds. (Stargate)
In the Stargate Atlantis episode Rising, Part 2 during the scene where colonel Marshall Sumner is being interrogated by the Wraith Keeper, the animal head present on the table bears a resemblance to that of a Mastadge.