Hmm... Onix.
Could it be the personification of the earth? A mixture of the creatures that tend to dwell in it (burrowing, digging, slithering, etc.) and the element in which it occurs (dirt, mud, stone).
Dunsparce. Perhaps it represents that those that are hidden from the sun's beauty, do not inherit it's beauty. That's all I could think of. xD
Mew. (Should be an easy one. ;))