Let's face it: that's one adorable frog. The trouble is that its relatives are all adorable too—adorable in the exact same way. Hyalinobatrachium frogs look remarkably similar, and since they're hard to find in the wild biologists sometimes have to turn to museum specimens instead. Preserved glassfrogs don't look like they do in real life, not just because their tiny eyes go all dead and cold, but because the act of preserving them changes certain physical traits. Melanophores, the pigment-containing cells that are responsible for black and brown markings in amphibians, can fade over time, especially if the specimen isn't properly cared for. And if all that distinguishes one species from another is a speckled pattern of brown dots on one frog's back, even the best biologists won't be able to see a difference once that pattern has faded away. Sometimes species look essentially identical in life, but live in isolated patches separately from each other. These distinct breeding groups might qualify as separate species if biologists can find the frogs in their natural habitat. Museum specimens just might not have enough information to differentiate populations from each other.