Sorry, my question was rhetorical in reference to existing species, not a search for prior art.
If Neanderthal and Cro-Magnon did recognize each other with special status, that would be more of an example of the level of equality that would need to functionally exist between two species in order for there to be a real "understanding".
That level of relative equality in no way exists between humans and cetaceans, so proposals to pretend that they deserve equal status seems illogical to me. What's next, chickens have eyes like humans so we can't eat them? Green beans react to stimulii, humans do too, no eating green beans?
Slippery slopes, thy name is PETA.