Biologists have discovered that a rare pink iguana found only on a single volcano in the Galapagos Islands is a surprising example of ancient evolutionary diversification—and Charles Darwin never even saw it.

Charles Darwin visited the Galapagos islands in 1835 but didn’t make it to the northernmost volcano, Volcan Wolf, which is the lone habitat for these pink lizards. Later travelers and scholars also seem to have missed or failed to report the curiously striped creature until 1986 when some Galapagos National Park rangers spotted the animals. Still, no scientists had looked into whether they represented a distinct species until now.

What they found was surprising. Instead of being some slight variation on the Galapagos iguana theme, the pink lizards represent a distinct and early branch of the genetic tree. The genomic analysis of the species suggests that they broke from other iguanas about five million years ago, much deeper in history than most other Galapagos species, like Darwin’s finches. In addition to the genetic differences, the pink iguanas also perform the characteristic mating ritual “head-bob” differently.