When a new pothos leaf grows, it extends and unfurls from an older leaf. Alternatively, a Philodendron produces a cataphyll that protects new leaves on the vine. A cataphyll is a paper thin, waxy, opaque sheath.
Instead of photosynthesis, a cataphyll’s main functions are storage, structural support, or protection. Definitely acting as a little protective layer for the emerging leaf, and then die. If you see a cataphyll growing from a stem node, then odds are it’s a philodendron and not a pothos.
Additionally, new philodendron leaves have a pink or brown tint. They darken as they mature. Pothos leaves unfurl a lighter shade than the original mature leaf color.