The Zaldans were a humanoid species characterized by webbed hands. They were known to the Federation, and information about them was included in the Federation database as early as the mid-23rd century.
As a culture, Zaldans were easily infuriated by courtesy, as they viewed it as a form of phony social behavior designed to cover true feelings. This fact was not lost on Wesley Crusher who, in 2364, entered into a conflict with a Zaldan Starfleet officer on Relva VII named Rondon, when he accidentally collided with him in a corridor. When Rondon became belligerent, Wesley responded in kind, averting a confrontation.
It was later revealed that the incident had actually been staged, as a way to test Wesley's appreciation of cultural complexities, as a part of the Starfleet Academy entrance exam. (TNG: "Coming of Age")
They were called Maldans in an early version of the Coming of Age script.
According to an internal reference document, listing all the aliens seen in Star Trek: The Next Generation, which was circulated around the time of the production of TNG Season 5, the Zaldans were given the description of "Federation race completely humanoid in appearance save for a webbed membrane between the fingers."