[simiones]

> consciousness effectively hits zero somewhere around reptiles

Note that at least one species of fish have been shown to very consistently pass the mirror test (they try to clean up a mark on their body they can only see in a mirror, then go back to the mirror to check, and repeat a few times). So, at least if you consider the mirror test to be a sign of consciousness in animals, then you might want to extend this to at least all chordata.

[xyzsparetimexyz]

The mirror test is just about intelligence. A p-zombie could easily pass it.

[simiones]

The mirror test is essentially the only pseudo-objective argument we have for believing that non-human animals are conscious - it proves that said animals have a concept of themselves as opposed to the rest of the environment. You are right that it is not necessarily very convincing, but I don't think we have anything much better.

Also, the entire point of p-zombies is that they can, by definition, pass any objective test that we can currently conceive. A p-zombie is, by definition, "something that behaves exactly like a human, but doesn't have any inner consciousness". Of course, just because we can define something at this high level doesn't mean that this thing can actually exist (e.g. we can define the concept "numbers that are bigger than 3 but smaller than 2", despite no such number existing).