On Earth, organisms including fish, reptiles, birds and mammals all share the same basic body plan - 4 limbs with 5 digits on each, a head with two eyes and a mouth, etc. If you started with a different body plan, and tried to explore permutations to occupy different ecological niches, what would you come up with? These creatures are a thought experiment, they are all descended from the same 6 legged "ancestor" skeleton, made with 123D Creature. This came out of a brainstorming session about how to use 123D Creature in teaching evolutionary biology, taking advantage of the feature that lets you re-use a skeleton and then sculpt a different creature.You can just print these critters as is. They will need to have support material enabled. I made sure to give their feet flat bottoms, so they should stick nicely to the build platform. If you have the 123D Creature iPad app, you can open them from the community (search for "mars evolution"), or you can open the "ancestor" skeleton and make your own variations.