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Apatosaurus: Facts About the 'Deceptive Lizard'

While Apatosaurus is sometimes still referred to by some outside of the scientific community as Brontosaurus, the name Brontosaurus was a result of a fossil mix-up.

American paleontologist Othniel C. Marsh named one of his fossil discoveries — an incomplete set of remains — Apatosaurus ajax in 1877. Two years later in 1879, he named a more complete specimen Brontosaurus excelsus. However, it was later learned that the bones that were used to reconstruct Brontosaurus were actually mostly from an Apatosaurus with the head of a Camarasaurus.

Once this mash-up of dinosaur fossils was sorted out, the name Apatosaurus took precedence since it was first. However, Brontosaurus is still a well-known moniker and remained in popular use until a few decades ago. The U.S. Postal Service even used the name in 1989 when it issued a series of dinosaur stamps, contending that the name was more familiar to the general public than Apatosaurus. The Flintstones' pet dinosaur, Dino, was also described as a Brontosaurus.

Infographic: skeleton of Apatosaurus dinosaur
Artwork by Scott Hartman reveals the bone structure of Apatosaurus.
Credit: © Scott Hartman / All rights reserved

The term Apatosaurus comes from the Greek words apate/apatelos, meaning "deceptive," and sauro, meaning "lizard." It was given this name because even before the Brontosaurus confusion, it was mistaken for a Mosasaurus, an aquatic reptile.

The herbivore Apatosaurus is a sauropod dinosaur that lived from about 154 million to 150 million years ago, during the Kimmeridgian and early Tithonian ages of the Jurrasic Period.

It is believed to be one of the biggest land animals to have roamed the Earth, with an average length of 75 feet (23 meters). Estimates of its weight have been as high as 39 tons (35,380 kilograms), but using modern modeling technology puts its average weight closer to 18 tons (16,329 kilograms). It was 85 feet (26 meters) long and 15 feet (4.6 meters) tall at the hip.

Like other sauropods, the vertebrae were made up of paired spines, producing a very wide and thick neck. But its neck was not as heavy as it might have been, thanks to a system of air sacs that kept it relatively light for its size.

Due to potential issues maintaining its blood pressure when its neck was held high — 17 feet (5.4 meters) off the ground — many scientists believe that the dinosaur held it nearly parallel to the ground for a good portion of the time.

Its legs were sturdier and not as elongated compared with other sauropods, such as Brachiosaurus, and its hind limbs were larger than its forelimbs. Like most sauropods, Apatosaurus had only a single large claw on each forelimb, with the first three toes on the hind limb possessing claws.

apatosaurus
Apatosaurus
Credit: Linda Bucklin | Shutterstock

Its tail was slim and possibly used as a whip to deter predators, but because it was so large it was possibly used to clear a path to food or even pull it toward its mouth.

It was a fairly slow and lumbering beast, but hatchlings of Apatosaurus were thought to have been able to run fairly quickly on their two hind legs to evade predators. However, full-grown Apatosauruses had little need to make a quick getaway.

Apatosaurus, like its close relative Supersaurus, had unusually tall spines on its vertebrae, which make up more than half the height of the individual bones.

The shape of the tail is slender when compared with other dinosaurs in its genus, due to the vertebral spines rapidly decreasing in height the farther they are from the hips.

Apatosaurus also had very long ribs compared with most other diplodocids, giving it an unusually deep chest. The apparently massive neck was, however, filled with an extensive system of air sacs to lighten the load.

Its skull is thought to be comparatively small at less than 2 feet (61 centimeters) long, but based on more recent research scientists believe it may have been somewhat larger. The skull contained pencil-shape teeth, suited to an herbivorous diet.

What did Apatosaurus eat?

It is believed that Apatosaurus primarily fed on low-lying plants, but its long neck may have enabled this sauropod to eat soft leaves on higher trees. Apatosaurus may have swallowed large chunks of plants without chewing and ingested stones to help with digestion.

Fossil finds

Apatosaurus fossils have been unearthed in Nine Mile Quarry and Bone Cabin Quarry in Wyoming as well as in areas of Colorado, Oklahoma and Utah.

Marsh discovered the first Apatosaurus in 1877 and followed that up with his inaccurate description of the Brontosaurus two years later.

In 1903, paleontologist Elmer Riggs re-examined the fossils and re-classified the Brontosaurus as Apatosaurus excelsus. Since Riggs published his opinions, almost all paleontologists have agreed that the two species should be classified together in a single genus.

Apatosaurus louisae was named by William Holland in 1915 in honor of Louise Carnegie, wife of Andrew Carnegie who funded field research to find complete dinosaur skeletons in the American West. Apatosaurus louisae is known from one partial skeleton which was found in Utah.

In 2008, footprints of a juvenile Apatosaurus were found in Quarry Five in Morrison, Colo. Discovered Matthew Mossbrucker, these footprints indicated that juveniles could run on their hind legs.

Infographic: Dinosaur profile of the plant-eating dinosaur Apatosaurus.
Learn about the Jurassic-era plant eating dinosaur Apatosaurus.
Credit: Ross Toro, Livescience contributor

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