There is a well-developed theory for the measurement of intelligence. And even if there wasn't, even a child can rank-order the intelligence of different anima

There is a well-developed theory for the measurement of intelligence. And even if there wasn't, even a child can rank-order the intelligence of different animals, or different humans that they personally know. It's true that trying to quantify the intelligence of creatures more intelligent than any we've seen before would constitute extrapolating beyond the dataset; this doesn't imply there is nothing beyond the dataset. Imagining that the current dataset limits the possible scope of outcomes is simple anchoring bias.