They are described as being bipedal, slightly taller than the average human, with two arms, four fingers on each hand. vestigial noses in the middle of their face and two eyes that are similar to human eyes but slightly larger in the front of their heads, small mouth under the nose, they have blood that is exactly like a humans, they eat the same food (although they can also digest meat uncooked). The major differences are more flexible bones, two joints on the elbow and spikes on the forearms and red skin (but it is skin, just as we have, and in different shades of red like we have different skin colours). Those similarities alone are absolutely remarkable on a biological level.
They sound like arborial decendents of Iguanadon to me. ;-)