This does not sound like the Droyne, nor does the description of the aliens’ lifestyle as it evolved in a corrosive atmosphere. However, other aspects of the adventure and some other traveller materials point clearly to the aliens of Shadows being Ancient Droyne.The pyramid structure on Yorbund was constructed perhaps 50,000 years ago by a minor alien race originating far to coreward. … The aliens themselves are vaguely reptilian, derived from quadrupedal carnivore stock; now upright, they utilize their thick tails for balance, incidentally freeing a three-fingered hand with twin opposable thumbs for grasping.
1. Shadows is part of a series of Ancients adventures
In CT Adventure 2, Twilight’s Peak, you’ll find this paragraph:
Together with these later adventures, Shadows is part of a series that puts the Travellers on the path of discovering that the Droyne are the Ancients, ending with an encounter with some actual Ancient Droyne beneath the Octagon shelter in Twilight’s Peak.… this adventure is itself an extension of two previously published Traveller adventures - Research Station Gamma (Adventure 2), and Shadows (part of Double Adventure 1).
2. The aliens in Shadows have Droyne coyns
In location 14 players may find a single gold Coyn, and in location 20 they may find the skeleton of one of the reptilian aliens with a pouch containing the rest of the set with 37 more such coyns. The coyn in location 14 is described as having a symbol of a flame on its face. This seems to be a set of 38 Droyne Coyns.
So who are these aliens? Their description indicates that they are not Droyne, yet their place in the series of adventures and the presence of an ancient set of Coyns would indicate otherwise. I wonder if the aliens in Shadows represent an early conception of the Ancients, which had changed by the time of Adventure 2, which contains Chirpers.