How do limb proportions provide clues to pigmentation and hairiness? I understand the environment part, but the inclusion of limb proportions I don't.
I am not positive on this one.
Limb proportions can determine whether the individual was arboreal or terrestrial, and this leads to an estimate of whether, and how much, the individual lived within a relatively dense tree canopy vs. the more open grasslands. If the latter, the individual would likely be more exposed to sunlight, requiring a better cooling system (i.e., less hair), but at the same time there would be more exposure to ultraviolet light, requiring darker pigmentation.
I got it. If the limb proportions most likely indicate he was terrestrial. From this they conclude hairless, and dark pigmented. Do those two features pretty much go hand in hand? At least in the environment this fossil was found?