Nigersaurus

Nigersaurus was one of the strangest dinosaurs ever discovered — a sauropod that defied nearly every expectation of what a long-necked dinosaur should look like. Unlike its towering relatives that reached high into trees, Nigersaurus kept its head perpetually angled downward, grazing on ferns and horsetails close to the ground. Its skull was wider than it was long, ending in a straight edge packed with hundreds of tiny teeth arranged in rows, creating a remarkably efficient plant-harvesting tool.

This medium-sized sauropod lived in what is now the Sahara Desert during the Early Cretaceous, when the region was a lush river floodplain teeming with life. Nigersaurus shared its environment with crocodile-like predators, giant fish, and other dinosaurs including the sail-backed Ouranosaurus. Its lightweight, highly pneumatized skeleton — filled with air spaces like a bird's — made it relatively delicate for a sauropod.

French paleontologist Philippe Taquet first collected Nigersaurus fossils during expeditions to Niger in the 1970s, but the bones were so fragile and fragmentary that describing the animal proved difficult. It wasn't until Paul Sereno's expeditions in the 1990s and 2000s recovered more complete material, including a remarkable skull, that scientists could fully appreciate this dinosaur's bizarre adaptations. Sereno named the species in Taquet's honor in 1999.

Perhaps most remarkably, CT scans revealed that Nigersaurus replaced its teeth faster than any other dinosaur known — roughly once a month per tooth position. Behind each active tooth sat a column of up to nine replacement teeth waiting in line, ensuring its dental battery never dulled despite constant grinding against gritty plants.