What Is a Sauropod? The Long-Necked Giant Dinosaurs

Q: What does quadrupedal mean?

A quadrupedal animal walks on all four legs. All sauropods, like Saltasaurus, were quadrupedal. So were the horned dinosaurs, the armoured dinosaurs, the plated dinosaurs, and most large duck-bills. Plant-eaters need huge digestive systems to break down tough vegetation, which means a huge gut shifts the body's centre of mass forwards, making two-legged walking impossible.

Q: Were there any small sauropods?

Yes. Magyarosaurus, which lived in what is now Romania during the Late Cretaceous, measured only about 6 metres from head to tail. At the time, Europe was a chain of islands, and small body size on islands is a well-known evolutionary pattern called insular dwarfism: when food is limited and predators are absent, animals tend to shrink over generations.

Q: How long was the longest neck?

The record-holder is probably Mamenchisaurus, a Chinese Jurassic sauropod whose neck reached an extraordinary 14-15 metres - longer than a school bus and roughly half its body length. The neck was built from 19 vertebrae (the highest count of any dinosaur), each hollow and laced with air sacs, braced by bony struts. The hollow neck bones were likely connected to a bird-like air-sac respiratory system.

Q: Who had the longest tail?

Diplodocus had one of the longest dinosaur tails, around 14 metres of it, built from about 80 vertebrae that became progressively smaller toward the whip-thin tip. Computer modelling has suggested that Diplodocus might have been able to flick the tip of its tail at supersonic speeds, producing a crack like a bullwhip, although this remains debated. The tail also acted as a counterbalance for the long neck.

Q: Did sauropods have thick skin?

Yes, sauropod skin was thick and tough. Fossilized skin from Saltasaurus reveals a knobby pebbled surface set with small bony plates called osteoderms - a kind of light armour unusual among sauropods. Other sauropods may have had smoother scalier skin. Some species may have had small spines or low ridges along their backs. Recent fossils have also shown some sauropods may have had soft tissue keels or sails along the back.

Sauropods were the long-necked, long-tailed, four-legged plant-eating dinosaurs - the largest land animals ever to have walked the Earth. They all shared the same basic body plan: a relatively small head perched on an enormously long neck, a barrel-shaped body supported by four pillar-like legs, and a long whip-like or club-like tail. Brachiosaurus, shown here, was 22 metres (72 feet) long and stood roughly 12 metres (39 feet) tall - taller than a four-storey building. All sauropods were strict plant-eaters, and although they belonged to the lizard-hipped saurischian group like the predatory theropods, they evolved in a completely different direction - towards sheer, world-record-breaking size.

Which was the biggest sauropod of them all?

Several sauropods compete for the title of biggest land animal of all time. Argentinosaurus, discovered in Argentina in 1987, may have been around 35-40 metres (115-130 feet) long and weighed up to 75-100 tonnes - as heavy as 15 African elephants. Patagotitan, also from Argentina, may have rivalled it, with one specimen estimated at 37 metres long and 60-70 tonnes. Supersaurus, from the Jurassic of North America, may have been the longest at 39-42 metres (128-138 feet). Because no complete skeleton of any of these giants exists, the exact "winner" is still debated - and there may be even bigger sauropods waiting to be found.

What does quadrupedal mean?

A quadrupedal animal walks on all four legs. All sauropods, like Saltasaurus, were quadrupedal. So were the horned dinosaurs (ceratopsians), the armoured dinosaurs (ankylosaurs), the plated dinosaurs (stegosaurs), and most large duck-bills. The reason is straightforward: plant-eaters need huge digestive systems to break down tough vegetation, which means a huge gut - and a huge gut shifts the body's centre of mass forwards, making two-legged walking impossible. Two-legged plant-eaters like Iguanodon only existed because they were small enough to balance over their hips, and even they often dropped to all fours.

Were there any small sauropods?

Yes - some sauropods were dwarfs by sauropod standards. One of the smallest is Magyarosaurus, which lived in what is now Romania during the Late Cretaceous. It measured only about 6 metres (20 feet) from head to tail - smaller than many cars. At the time, Europe was a chain of islands, and small body size on islands is a well-known evolutionary pattern called insular dwarfism: when food is limited and predators are absent, animals tend to shrink over generations. The same process produced dwarf elephants on Mediterranean islands much more recently.

How long was the longest neck?

The record-holder is probably Mamenchisaurus, a Chinese Jurassic sauropod whose neck reached an extraordinary 14-15 metres (46-49 feet) - longer than a school bus and roughly half the length of its entire body. The neck was built from 19 vertebrae (the highest count of any dinosaur), each one hollow and laced with air sacs to keep it light, and braced by bony struts that made the neck stiff and strong. The sauropod's hollow neck bones were likely connected to a bird-like air-sac respiratory system, which would have helped pump oxygen efficiently through the giant's body.

Who had the longest tail?

Diplodocus had one of the longest dinosaur tails - around 14 metres (46 feet) of it, built from approximately 80 vertebrae that became progressively smaller toward the whip-thin tip. Computer modelling has suggested that Diplodocus might have been able to flick the tip of its tail at supersonic speeds, producing a crack like a bullwhip - although this remains debated. The tail also acted as a counterbalance for the long neck, balanced over the hip joint like a giant see-saw. Diplodocus probably did not drag its tail along the ground, despite older illustrations showing it that way.

Did sauropods have thick skin?

Yes - sauropod skin was thick and tough, although its exact texture varied between species. Fossilized skin impressions from Saltasaurus reveal a knobby, pebbled surface set with small bony plates called osteoderms - a kind of light armour unusual among sauropods. Other sauropods may have had smoother, scalier skin similar to that of a modern reptile. Some species, including some titanosaurs, may have had small spines or low ridges running along their backs. Recent fossils have also shown that at least some sauropods may have had soft tissue keels or sails along the back.

More Dinosaur Facts

Sauropod babies were tiny compared to their parents - the infant Mussaurus ("mouse lizard") was only about 30 cm (12 in) long, though adults reached 6 metres.
Sauropod bones were sometimes used in traditional Chinese medicine - locals once called them "dragon bones" and ground them up to feed to children.
Despite having necks longer than buses, sauropods had brains smaller than a tennis ball.
The largest land animal alive today, the African bush elephant, weighs only about a tenth as much as the largest sauropod.
A sauropod heart had to pump blood up to a head as much as 12 metres above the ground - it was probably enormously powerful, perhaps with multiple chambers.

What is a sauropod?