Swabb

Swabb was the first mate of Captain Kaliko on the Black Gold. He was really in league with Oil Corp., who promised him a proper body. His race is unknown, but his appearance was a human skeleton. The rest of the crew of the Black Gold were the same.

Swabb turned on Kaliko when he thought the Doctor and Martha Jones were Oil Corp. spies. He controlled the Oil rigs to attack the ship, and it was destroyed. Swabb survived, and threatened Martha to use her body to replace his. The Doctor used his Sonic screwdriver to flip Swabb off the deck. Swabb survived the fall, vowing revenge. His subsequent fate is unknown.

Like his Black Gold crewmates, it is not known exactly how or why Swabb ended up as a living skeleton. (DW: The Infinite Quest)

Behind the scenes
Although the story does not follow this detail, Swabb's interest in taking on Martha's body might be an LBGT reference.