Sauropods were the heaviest animals ever to walk on land
Sauropoda—lizard-footed saurischian dinosaurs—carried very long necks and tails, small heads relative to bulk, and four pillar-like legs. Some species reached the largest sizes of any land animal. Famous genera include Apatosaurus, Brachiosaurus, Diplodocus, and Argentinosaurus.
Unequivocal sauropods appear in the Early Jurassic; claimed Triassic forms such as Isanosaurus and Antetonitrus had their ages or status questioned, though Late Triassic sauropod-like tracks from Greenland’s Fleming Fjord Formation hint at earlier presence. By the Late Jurassic about one hundred fifty million years ago the group was diverse and widespread. Othniel Charles Marsh coined Sauropoda in eighteen seventy-eight from Greek for lizard foot.
Complete skeletons are extremely rare. Many species, especially giants, are known from scattered bones; near-complete finds often lack heads, tail tips, or limbs. They were herbivorous quadrupeds, usually long-necked, often with spatulate teeth, tiny heads, massive trunks, and long tails. Hind feet were club-like with five toes but claws mainly on the inner three or four; forelimbs were slenderer pillars.
Popular culture fixed on their enormity, yet the fossil record forces humility: the biggest bodies are puzzles assembled from fragments. Still, the body plan—neck for high browsing, column legs for mass, small head to lighten the cantilever—remains one of evolution’s clearest megafaunal designs.
The numbers are staggering. Argentinosaurus may have weighed 65 to 80 tonnes, against at most 10.4 for today's largest land animal, the bush elephant, and Supersaurus stretched 33 to 34 metres. Necks topped 15 metres, six times longer than any giraffe's on record, carried on as many as 19 neck vertebrae where nearly all mammals have seven. The trick was air: bird-like sacs hollowed the vertebrae until some were about 60 percent empty space, so much that one nineteenth-century specimen, Ornithopsis, was first mistaken for a pterosaur. Feeding was relentless too; Nigersaurus seems to have replaced each tooth every 14 days. At the other extreme, the island dwarf Europasaurus grew to just 6.2 metres.
Source: Sauropoda
