Photos by renan_ozturk / words by m_synnott / The goal of the 2021 natgeo Lost World Expedition was an "elevational transect" of the Upper Paikwa River Basin, near Guyana’s northwestern frontier with Brazil and Venezuela, to look for new species of amphibians and reptiles in one of the world’s richest and least explored hotspots of biodiversity. The final section of our transect led us through a pristine, untouched cloud forest and culminated with a first ascent of a 7,000-foot tepui called Weiassipu. The expedition was led by dr_bruce_means, an intrepid 80-year-old ecologist and evolutionary biologist whose life’s work has been to catalog and document the unique flora and fauna of South America’s tepui region. Tepuis, which rise high above the rainforest like tabletop mesas, are made from some of the oldest rock on Earth, iron-hard, orange quartzite that is 1.6 to 1.8 billion years old. These “lost worlds” represent the last vestiges of an ancient plateau called the Guiana Shield, an...