Sauropodomorpha

The Sauropodomorpha began as relatively small animals. Early members, such as the Eoraptor-grade taxa from the Late Triassic Ischigualasto Formation and the later European Plateosaurus, were bipedal dinosaurs measuring between 2 and 8 m. Their serrated, leaf-shaped teeth indicate they were likely omnivorous. Over roughly 30 million years, their descendants transitioned to four-legged movement and grew significantly. They developed exceptionally long necks and column-like limbs, achieving body masses far greater than any previous terrestrial animal.

The evolution of sauropods involved several interconnected adaptations. A small head reduced the mechanical strain on the long neck, which was itself lightened by air-filled vertebrae linked to a bird-like respiratory system. These dinosaurs consumed large amounts of high-fibre plants with minimal chewing, relying instead on massive guts for fermentation. Sturdy, columnar limbs provided the necessary support for their enormous weight. Within the group, different lineages evolved specialized feeding habits. Diplodocids were suited for horizontal browsing near the ground, while titanosaurs and brachiosaurids developed the ability to reach high into the canopy.

The clade thrived for 165 million years and was found on every continent. Titanosauria, the most successful lineage of the Cretaceous, was globally distributed and included the largest animals ever to live on land.

Sauropods were bulk herbivores that consumed conifers, cycads, ginkgos, ferns, and eventually flowering plants. Their strategy involved swallowing leaves whole and processing them in their digestive tracts. Fossil trackways provide evidence that these animals travelled in herds. At nesting sites like the Auca Mahuevo colony in Argentina, researchers have found tens of thousands of egg clutches, indicating communal nesting. Hatchlings weighed about 5 kg, but analysis of bone histology suggests they grew rapidly, sometimes doubling their mass every year as juveniles and reaching maturity within 20 to 30 years. Species often coexisted in the same environment by occupying different ecological niches, defined by their varying neck lengths and tooth shapes.

• Plateosaurus engelhardti Trossingen quarry — dozens of articulated individuals, multiple European museums.
• Massospondylus carinatus Rooidraai nesting site — Early Jurassic eggs and embryos, Bernard Price Institute, South Africa.
• Brachiosaurus altithorax holotype (FMNH P 25107) — Field Museum.
• Auca Mahuevo titanosaur eggs (MCF-PVPH) — embryos with skin impressions, Patagonia.

Whether prosauropods (the basal, pre-sauropod sauropodomorphs like Plateosaurus) form a real clade or a paraphyletic grade has flipped multiple times. Current consensus treats them as a grade. Maximum sauropod size estimates (Argentinosaurus, Patagotitan, Bruhathkayosaurus, Maraapunisaurus) are contested because the largest specimens are mostly fragmentary; published mass figures swing by ±30% per study. The thermal physiology of giant sauropods — full endothermy vs gigantothermy / inertial homeothermy — is also unresolved.

Brachiosaurus's wide-eyed appearance in Jurassic Park (1993) is one of the most famous sauropod scenes ever filmed. Apatosaurus / "Brontosaurus" remains the platonic dinosaur shape in children's books, despite long having had its head replaced and its name argued over.

• diplodocidae
• brachiosauridae
• diplodocus
• brachiosaurus
• argentinosaurus
• patagotitan

• Sander, P. M., et al. (2011). Biology of the sauropod dinosaurs: the evolution of gigantism. Biological Reviews, 86, 117–155.
• Yates, A. M. (2007). The first complete skull of the Triassic dinosaur Melanorosaurus. Special Papers in Palaeontology, 77, 9–55.
• Carballido, J. L., et al. (2017). A new giant titanosaur sheds light on body mass evolution among sauropod dinosaurs. Proc. R. Soc. B, 284, 20171219.
• Wedel, M. J. (2003). Vertebral pneumaticity, air sacs, and the physiology of sauropod dinosaurs. Paleobiology, 29, 243–255.