The Sargasso troops were yellow winged humanoid bat-like aliens. They had pointy ears on the top of their heads that could project energy. They were also roughly the same size as a human, and had the ability of flight.
It is possible that they were not a race at all, but rather just the male members of Sirena's race. This is conjecture based upon the fact that they were the only males who were seen and the only green skinned humanoid seen was Sirena herself, who was clearly female.
This isn't a stretch, it is entirely possible that both genders of the same species could look drastically different. As an example, the Culacaon males were humanoid, but the females resembled giant snails.