These 30-ton Apatosaurus are giant fortresses of flesh. However, they are too large to attack, even by fully grown Allosaurus.
— Allen, describing Apatosaurus

Apatosaurus (a-pat-oh-sore-us; name meaning “Deceptive Lizard") originally known as Brontosaurus (which means "Thunder Lizard"), is a genus of giant herbivorous sauropod dinosaur that lived during the Late Jurassic period in the United States of America, 154-145 million years ago. It belongs to the Diplodocidae Sauropods, obviously a relative of Diplodocus. It was a 23-27 meters long, bulky 35-40 tonne sauropod; a 'fortress of flesh'. As such, they were hunted by creatures, such as Allosaurus and other predators. It is arguably the most famous sauropod dinosaur.



Apatosaurus lived during the Late Jurassic Period 155-145 million years ago. It shared the environment with other herbivores, including other sauropods, as well as Dryosaurus, Stegosaurus, and Allosaurus. They were first discovered and named by Othniel Marsh in 1877 because the chevron bones were similar to those of a prehistoric marine lizard, Tylosaurus.



Apatosaurus was one of the largest sauruopds of the Jurassic and as well as one of the largest dinosaurs the ever existed. They grew to a staggering 15-20 feet (4.5-6 m) tall at the hips, measured 70-75 feet (21-23 m) in length, and weighed up to 30 tons (60,000 lbs.), more than 12 times heavier than an elephant.

Apatosaurus were prey for most predators, described as "giant fortresses of flesh", but were too large for any predator to attack, even the largest fully grown Allosaurus. Only the young, injured, sick or old were at risk of predation. However, a healthy old individual could be virtually untouchable beyond a certain age, for sheer size alone. A lone Allosaurus, or even a pack, could stand little chance of taking on a fully grown and mature Apatosaurus, hence why they would likely target smaller, weaker and generally more vulnerable animals.

Apatosaurus was heavy, with a long muscular neck and elephant-like legs. It, like their close relatives Diplodocus, had a long whiplike tail that may have been used as a defense against large predators such as Allosaurus. It also had a sharp claw on each thumb that may have deterred attackers when it reared up on its hind legs to defend itself or reach for higher vegetation. 


Like all sauropods and other kinds of herbivorous dinosaurs, Apatosaurus were dinosaurs that traveled in herds and probably migrated looking for food throughout the year from area to area. Herds of adults and sub-adults would collectively have weighed hundreds of tonnes, all moving together.

These dinosaurs had to eat a lot of food to keep their massive bodies going. They had to have an enormously long gut to digest all the plant material that it ate. They may have swallowed plant matter whole and ground it up with a gizzard, much as birds do today to grind up there food. They did this because they had very weak chewing teeth but had perfect nipping incisors to pull a vegetation.