Dax's species

From Memory Alpha, the free Star Trek reference.

Not to be confused with the Trills, which were the species of the Dax symbiont's hosts.

Dax's species was a humanoid species from the Alpha or Beta Quadrant. By 2293, members of this species were serving on Starfleet vessels.

They had some enhanced facial features, though their most distinguishing characteristic was their large, unusually-shaped feet, which made it impossible for them to wear the same footwear as most humanoids. This species apparently did not have footwear of its own either, making their feet that much most noticeable. (Star Trek VI: The Undiscovered Country)