u/DanteDilphosaurus

I want to start a project based on a lineage of aliens that evolved from ancestors with only 2 front fins, I'm wondering if this would be plausible for land life and how the aliens would evolve. They would be vertebrates/vertebrate analogs and would evolve on a relatively low gravity planet maybe around 0.5 to 0.6g with a higher oxygen percentage than earth. Would it be plausible for them to become tall 2 legged herbivores kind of like the striders from no mans sky. Is it actually plausible for an ancestral vertebrate to start out with 2 fins or would it likely evolve 4 fins before it moves onto land. If the strider body plan is implausible what would be a more realistic body plan for complex 2 legged life. I imagine the legs would evolve from the pectoral fins.