There are plenty of examples of convergent evolution around (i.e. unrelated creatures displaying similar features).
Wolves look very similar to thylacines (marsupial 'wolves'), yet are more closely related to Man. Good point about cephalopods and vertebrates independently evolving eyes -- box jellyfish have nicely developed eyes, too, I seem to remember.
However... lots of things have rundimentary vision -- after all, it's just a development of sensory pits found on plenty of Cambrian animals (trilobites, for example). Similarly, the thylacine/wolf similarity occurred because both are running quadruped predators -- long limbs, big jaws, etc.
Flight feathers are a different matter, however. There's no easy path of progression from scales to flight feathers -- down (or fur), yes; flight feathers, no. Indeed, the whole development of flight is a pretty suspicious business anyhow. Compared to flying, this eye business is a piece of cake...
In conclusion, there were the beginnings of visual organs in most early creatures, and it is not unreasonable to assume that Coelentrates (jellies and anemones), vertebrates and cephalopods had a common ancestor capable of light/dark perception. Similarly, whether feathered flight evolved alongside the dinosauria or from it, it is likely only to have evolved once in its rudimentary form (i.e. to the point where it slows falling or assists jumping and hence provides selection pressure for flight).
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Wolves look very similar to thylacines (marsupial 'wolves'), yet are more closely related to Man. Good point about cephalopods and vertebrates independently evolving eyes -- box jellyfish have nicely developed eyes, too, I seem to remember.
However... lots of things have rundimentary vision -- after all, it's just a development of sensory pits found on plenty of Cambrian animals (trilobites, for example). Similarly, the thylacine/wolf similarity occurred because both are running quadruped predators -- long limbs, big jaws, etc.
Flight feathers are a different matter, however. There's no easy path of progression from scales to flight feathers -- down (or fur), yes; flight feathers, no. Indeed, the whole development of flight is a pretty suspicious business anyhow. Compared to flying, this eye business is a piece of cake...
In conclusion, there were the beginnings of visual organs in most early creatures, and it is not unreasonable to assume that Coelentrates (jellies and anemones), vertebrates and cephalopods had a common ancestor capable of light/dark perception. Similarly, whether feathered flight evolved alongside the dinosauria or from it, it is likely only to have evolved once in its rudimentary form (i.e. to the point where it slows falling or assists jumping and hence provides selection pressure for flight).
Hope that made sense. --L.