[Sapphire]

There's a term, "homologous structures", I believe, which refers to a similar, evolved structure of a body part across unrelated species. This occurs because the animals fill a similar niche, or have a similar need for a structure like that. In this case, the "finger-face" look would probably be a homologous structure, a trait that's simply common throughout the Oddworld creature design spectrum. Other things, like no eyes, thick forearms and skinny upper arms, residual tails and limbs that end in a single claw are probably things that the artists use to tie all of the creatures together and make them feel like they belong in the same world.