Russell today started explaining something to me about sharks living in dens. It sounded plausible to me, and he's probably better informed about sharks than I am, so I just said, "Really?"
A minute or two later he added brightly: "Julie, did you know that sharks sometimes catch fish, and then they use it as wallpaper or insulation for their home. And then they pile rocks around it and catch more fish."
I suppose sharks are also outvertebrates. That's what Russell insists non-invertebrate animals are.