“You would think they are somehow protective but really they are a decoy there for blocking the teeth or claws of whatever wants to eat them,” Mr. Scherz said of the giant scales. “They get stuck in those jaws or claws and allow the gecko to escape naked and alive.”

Fish-scale geckos have long mesmerized herpetologists with their Houdiniesque escapes, but scientists are still not sure how many species of the lizards exist. A genetic analysis in 2013 suggested there might be about 10 species, but, including the new discovery, only five have been recognized so far. Researchers are working to confirm the new species through different methods.

Mr. Scherz and his colleagues ascertained that G. megalepis was its own species by using a micro-CT scan to compare its skeletal structure with the previously recognized species of Geckolepis. The subtle differences they found in its eye bones and other parts of its body, in addition to the enormous size of its scales, led them to determine that it was distinct, and the first new Geckolepis to be discovered in about 75 years.

Though Mr. Scherz has never grabbed G. megalepis in the wild, he said he had had plenty of experiences trying to snag their kin. Because of their speed, agility and tearaway scales, “they are nightmares to catch.”