By | September 9, 2016

The diplodocoids were a group of giant plant-eating dinosaurs that walked on all fours. They had incredibly long necks, balanced by even longer whiplike tails, which they used to lash out at enemies. Their legs were longer at the back than the front, which may have helped them to stand up, using the tail as a prop. One of the largest diplodocoids was Amphicoelias—a dinosaur as long as a football field and as heavy as a blue whale.


Key features
■ Long, flexible necks
■ Long, slender tails
■ Small heads and large bodies

Diplodocoids first appeared in the Middle Jurassic, 170 million years ago. They died out at the start of the Late Cretaceous, 99 million years ago.

Dicraeosaurus (DIE-cray-oh-SORE-us)


When: 150 million years ago (Late Jurassic)

Fossil location: Tanzania

Habitat: Woodlands

Length: 39 ft (12 m)

Diet: Plants

Dicraeosaurus had a shorter neck than other diplodocoids, so it probably fed on bushes rather than trees. Its tail was also shorter, which suggests it wasn’t used like a whip. A layer of skin may have stretched between bony spines that ran along the dinosaur’s neck and back, forming a sail. This perhaps helped to regulate body temperature, or it may have been used for defense or communicating with other members of the species.

Diplodocus (dip-LOD-oh-kuss)


When: 150–145 million years ago (Late Jurassic)

Fossil location: USA

Habitat: Plains

Length: 82 ft (25 m)

Diet: Leaves

Diplodocus is the longest dinosaur known from a complete skeleton. It had an incredibly long tail—as long as the rest of its body— which it could move at an amazing speed, creating a whiplike crack. Diplodocus’s neck was almost three times the length of a giraffe’s neck and was probably held up at a high angle. Its backbone was strong enough to support its enormous weight, but the bones were hollow. Some scientists think it was a tree-browser, using the peglike teeth at the front of its jaws to strip leaves off branches.
Others think it couldn’t lift its head high enough and probably swung it from side to side to browse on low shrubs. Diplodocus may have grown at a very fast rate, taking around 10 years to become a full-sized adult.



Diplodocus’s skeleton

To support its long neck and tail, Diplodocus’s backbone acted like the cables in a suspension bridge. The cables take the weight of the road (the neck and tail) and pass it down through the piers (the legs), which anchor it to the ground.

Amargasaurus (ah-MAR-gah-SORE-us)


When: 130 million years ago (Early Cretaceous)

Fossil location: Argentina

Habitat: Woodlands

Length: 36 ft (11 m)

Diet: Plants

This relatively small and short-necked diplodocoid was unusual because it had a double row of spines running along its neck and back that became a single line down its tail. There may have been a web of skin running between the spines, forming a double sail. Why it had a sail on its back is a mystery, but perhaps Amargasaurus used it for display. Some scientists think it didn’t have a sail and simply rattled the spines to make a noise.

Apatosaurus (a-PAT-oh-SORE-us)


When: 150 million years ago (Late Jurassic)

Fossil location: USA

Habitat: Woodlands

Length: 75 ft (23 m)

Diet: Plants

Weighing as much as four elephants, Apatosaurus (or Brontosaurus, as it is popularly known) was shorter and heavier than its relatives, with thicker legs. Some scientists think that instead of rearing up to feed from trees, Apatosaurus may have used its strong limbs and massive weight to knock trees down, as elephants do today. Pencil-like teeth lined the front of its broad muzzle.



The Morrison Formation in the US has revealed many bones and footprints of giant diplodocoids such as Apatosaurus and Diplodocus, along with fossils of the trees and plants they ate.

Barosaurus (BAH-roe-SORE-us)


When: 155–145 million years ago (Late Jurassic)

Fossil location: USA

Habitat: Plains of N. America

Length: 92 ft (28 m)

Diet: Plants

The first Barosaurus remains were found during the “Bone Wars” of the late 1800s, when a number of fossil hunters raced to out-do each other with new dinosaur fossil discoveries. In 1922, three Barosaurus skeletons were found at Carnegie Quarry in Utah, suggesting that Barosaurus may have roamed in herds.

Feeding on stones Barosaurus’s large peglike teeth were perfect for pulling leaves off trees, but not for chewing them. Some scientists thought it swallowed stones to help grind food in its stomach, but recent research has shown that it used bacteria in its gut to digest food.

Sticking its neck out?

In 1993, a model Barosaurus was mounted rearing on its hind legs. Some scientists think this position is incorrect—the heart could not have been strong enough to pump blood vertically upward to the brain. New research suggests that with the right-sized heart, this is indeed possible.

Spiny back

No one is sure why Barosaurus had spines running along its back—they may have been used for defense, or may simply have been a decorative feature. These spines were bony plates fixed in the skin and were not attached to the skeleton. Barosaurus’s rough, scaly skin gave it much needed protection against scratches and bite wounds. It also helped reduce moisture loss from its body when the climate turned dry.


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