Was this six-meter predator the first true dinosaur to roam the ancient Earth?

Nature · Published 3 October 2026 Swipe more like this →

In short: Discovered by an Andean goatherd in 1959, Herrerasaurus is a key to understanding the dawn of the dinosaur age. This Late Triassic carnivore, found in Argentina, has sparked decades of scientific debate over whether it represents the very base of the dinosaur family tree or a separate evolutionary experiment.

Herrerasaurus ischigualastensis lived during the Late Triassic period, roughly 231.4 million years ago. Its fossils were first unearthed in the Ischigualasto Formation of northwestern Argentina. The genus was named by paleontologist Osvaldo Reig to honor Victorino Herrera, the goatherd who initially spotted the remains in 1959. For years, the creature's classification remained elusive, with researchers variously labeling it a basal theropod, a sauropodomorph, or even a non-dinosaurian archosaur.

The mystery began to unravel in 1988 when a team led by Paul Sereno discovered a nearly complete skeleton and skull. This find provided the anatomical detail necessary to place the animal within the saurischian lineage. Measuring up to 6 meters in length and weighing approximately 350 kilograms, this bipedal predator possessed powerful hind legs and a relatively small head. Its discovery has been central to defining the monophyly of dinosaurs, forcing scientists to distinguish between traits inherited from a common ancestor and those that evolved independently through convergence.

The debate persists because the early evolution of dinosaurs was a period of rapid radiation. Some experts argue that if Herrerasaurus was a primitive theropod, then the major dinosaur lineages must have diverged much earlier than previously thought—potentially before the middle Carnian stage. This hypothesis is bolstered by the existence of large, three-toed footprints in older rock layers, which suggest that theropod-like dinosaurs were active millions of years before the known fossil record of Herrerasaurus itself. As a result, this predator remains a vital, if contested, link in the story of how dinosaurs became the dominant terrestrial life form of the Mesozoic Era.

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