Sauropods are a suborder of Saurischia ("lizard-hipped"), one of the two categories of dinosaur, the other being Ornithischia ("bird-hipped"). Sauropoda is one of the two great lineages of herbivorous dinosaurs alongside Ornithischia, which includes duck-billed dinosaurs, triceratops, stegosaurus, and many others. Sauropods are famous for being the largest land animals in the history of life on Earth.
Sauropods first emerged in the late Triassic period, 200 million years ago. The first sauropods were small by sauropod standards — 5 m (16 ft) in length, and a few meters tall, weighing about a ton. The early sauropods would have been roughly the size of an elephant. They would have been able to avoid predation due to their sheer size. Sauropods also possess long, tapering tails, which many paleontologists believe could have been cracked like a whip, producing sonic booms as loud as 200 decibels. Computer simulations have shown this would have easily been within the animal's capabilities. There is also circumstantial evidence, fossils of sauropods with fused or broken tail vertebrate.
By the late Jurassic, 150 million years ago, sauropods spread to every continent, where their fossils can still be found today. From very early in their evolution, sauropods grew to tremendous sizes. Some of the largest known are Brachiosaurus, thought for many decades to be the largest dinosaur; Supersaurus, the longest verified dinosaur at 40 m (130 ft) in length; Diplodocus, one of the most famous of sauropods; and Sauroposeidon, with the longest neck out of any known creature, at 18 m (60 ft). There is some sketchy evidence — literally just sketches, as the only fossil crumbled to dust over a century ago — for a sauropod rivaling the size of a Blue Whale, or Amphicoelias fragillimus, which would have been 40–60 meters (131–196 ft) in length and weighed 120 tons.
Sauropods had peg-like teeth that were adapted to stripping the leaves off of trees. They did not use them to chew, but rather had numerous large stones in their stomaches, called gastroliths, which ground up the leaf matter and helped digest it. Sauropods were an extremely successful suborder as they were able to reach high-up leaves that no other type of dinosaur would have been close to reaching.