For nearly two decades, no one had spotted the world’s smallest-known snake. Some scientists worried that maybe the Barbados threadsnake had become extinct, but one sunny morning, Connor Blades lifted a rock in a tiny forest in the eastern Caribbean island and held his breath.

The Barbados threadsnake was among 4,800 species of plants, animals and fungi once believed to be lost to science.

I was making a joke and in my head I said, ‘I smell a threadsnake,'” Justin Springer, Caribbean program officer for the NGO Re:wild, recalled. “I just had a feeling, but I couldn’t be sure because we turned over a lot of rocks before that and we saw nothing.