Meskeen

The so-called "Captain's race", the Meskeen are an amphibious race that resemble terran frogs with digits. They occupy almost the same positions in the ISC as Humans do in the United Federation of Planets, having similar intellectual abilities, ambition, and assertiveness. Meskeen do not die of old age, or stop growing, consequently the oldest being thousands of years old and five meters tall, yet the average Meskeen is about the same size and composition as a human.

(Star Trek: Starfleet Command II-Empires at War).