Sulfur-based lifeforms that were driven to extinction on their world, but who preserved their species with an advanced Gadmeer terraformer ship that transplanted their DNA and cultural records to a new homeworld. A highly intelligent and peaceful species that once thrived for some 10,000 years, the Gadmeer were wiped out by an enemy with whom they were at war many hundreds of years ago -- possibly the Goa'uld.
The Gadmeer are somewhere between lizards and insects physiologically. They are bipedal and primarily upright, and are green with long tails. Their faces are beaked by a hummingbird-like protrusion. Their heads are large with cylindrical eyes, which might be an indicator to their intelligence. Protruding from the back of their heads is some sort of conduit, or tether, which connects into the back.
To prevent the loss of their entire civilization, the Gadmeer constructed a space-fairing terraformer, in which massive databanks stored the genetic codes of all the original world's lifeforms, music, and other cultural records. The Gadmeer were authors of beautiful art, particularly music, but samples of the art are so alien to humanoid ears that is, frankly, painful to listen to. Their ship was designed to search the galaxy and scan all planets it encountered, and compute suitable replacement planets to settle and ultimately rebuild the civilization.
Because the creatures live in a sulfur-based environment, the target planet's atmosphere had to be terraformed to meet their needs. Unfortunately, after a planet was found and the process began, it was discovered that SG-1 had relocated a lost tribe of Enkarans to the planet. Jack O'Neill attempted to destroy the terraformer -- and the remains of the Gadmeer civilization -- rather than let it wipe out the Enkarans, who could not be relocated to another world. But with the help of Daniel Jackson, Lotan, an artificial lifeform created by the ship to interface with the Enkarans, learned that the ship had found the original Enkaran homeworld and returned the lost tribe.
It is presumed that the ship was successful in returning to the planet to finish the terraforming process, and giving new birth to the advanced Gadmeer race. But because the environment is now hostile to human life, future contact by Earth seems unlikely.
Scorched Earth - SG-1 learns of an ancient species, the Gadmeer, that built a vessel to carry their genetic code to rebirth their species on a new world before going extinct.