The curtained letti replaced its ancestor and spread to the north and south taiga of Mason. The curtained letti gets it's name from the way it's "eyes" are set up. A short internal spine of rigid muscles provides support to these for part of there extent after which they hang limp. The spines are attached to many musses in the head that allow them to be move 90 degrees both horizontally and vertically giving the organism a large range of vision
Other changes include the breathing tube being open at both ends and narrowing sharply at the rear allowing the organism to "snort" for an emergency speed burst, the first pair of legs being moved to the front in order to better act as gaspers during feeding while the hind pair are lost and the apparency on a tail ending in the cloaca that is used as an ovipositor which allows laying of eggs without having to land.
In order to remain in the air longer the curtained letti retains some of the nitriods it sucks up during fulling in the gas bags. It then feeds them N2 collected from the atmosphere to stimulate ammonia production. As a result of this behavioral adaptation it can remain airborne for more than twice as long at a stretch when compared to its ancestor.