Sauropods

No group of animals has ever matched the sheer physical scale of the sauropods. Patagotitan, Argentinosaurus, and their titanosaurian relatives reached masses exceeding 70 tonnes — more than twice a blue whale. Yet sauropodomorphs began humbly: the first members, like Plateosaurus in the Late Triassic, were modest bipedal browsers around 8 meters long.

The transition from prosauropod to true sauropod in the Early Jurassic marks one of the most consequential evolutionary shifts in dinosaur history. Quadrupedalism, columnar limbs, and extreme neck elongation — all evolved together as a feeding strategy for exploiting tall vegetation inaccessible to competitors. By the Late Jurassic, sauropods had achieved a near-global distribution, with the Morrison Formation of North America and the Tendaguru beds of Africa preserving some of the most spectacular assemblages.

The Cretaceous brought the rise of titanosaurs — a diverse group that survived until the very end of the Mesozoic and achieved global reach, with well-known forms on every continent. Their success was partly due to extreme reproductive strategy: titanosaurs laid large clutches of small eggs, sacrificing parental investment for sheer numbers. By the time the asteroid struck, sauropods had been Earth's largest land animals for over 150 million years.