Not an evolutionary specialist, but was wondering about the evolutionary processes that goes from : what I understand was water based life to land based walking animals.

I think a Snell might be considered to have 1 foot. But then creatures jump to 4, 6, 8 and centipede millipedes . Bipedal being rare I think. Then maybe somewhat lastly winged creatures with feet.

If evolutionarily processes invents a new creature that doesn't survive long then it just could not survive to reproduce to keep population flourishing.

So, what is it about the odd numbered feet that is not as evolutionarly fit? Why no abundance of 1 foot, 3 feet, 5 feet, 7 feet equiped creatures?