Aurelians were a bipedal, ornithoid race. They stood taller than most Humans, and had bright yellow feathers and blue eyes. Although resembling birds, the Aurelians did have an additional set of humanoid appendages (an extra pair of arms) allowing them the capability of using devices like a tricorder. (TAS: "Yesteryear")
The Aurelian species were identified by name in the script of "Yesteryear" by way of identifying Aleek-Om. Furthermore, in the stage directions from the script, he was described as "a native of the planet Aurelia, and he is a bird-like creature of blue-green hue." In the actual episode, he is instead a golden color. The novelization of "Yesteryear" (in Star Trek Log 1) describes the Aurelian Aleek-Om as having an "intricate scroll" – a sign of manhood – tattooed on his beak, "wide, black eyes," as well as a "brilliant gold and blue-green plumage."
The Aurelians very much resemble the Skorr, as the animated Aurelian character design was reused for the Skorr as a budget-saving measure. (Star Trek Magazine issue 158, p. 52) In the text commentary to "Yesteryear", Aleek-Om is even described as a member of the Skorr. The Aurelians were not the only species to be reused in TAS; the swooper animations were also used, modified slightly, for the Maravel dragon and mechanized sentinel.