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Anchisaurus Dinosaur Facts | Yaleosaurus

The Anchisaurus, originally known as Megadactylus but also frequently referred to as Yaleosaurus, is a small prosauropod dinosaur that lived at the end of the Triassic and early Jurassic era some 194 million years ago. The prosauropods would have been an intermediate species between the first bipedal herbivorous dinosaurs and the late sauropod giant as the Diplodocus. This evolution was necessary because having to digest plant matter required that herbivorous dinosaurs have a large intestine. As the bowel is positioned in front of the pelvis, it became increasingly difficult to stay on two legs.

First discoveries

Fossile de Anchisaurus

The first discoveries of Anchisaurus remains were made well before anything was known about the dinosaurs and these are the first fossils to be dug up in North America. It was in 1818 that a small skeleton was found in the sandstone of a building material quarry in Connecticut, USA, and it was initially thought that it was human remains. Gradually, the finds multiplied in Massachusetts and the number of bones began to accumulate. By 1855, the remains were recognized as being reptilian in nature. Edward Hitchcock first collected these bones under the name of Megadactylus in 1865. The name Anchisaurus was only officially granted to this dinosaur in 1885 by the famous paleontologist Othniel Charles Marsh and the Megadactylus became an integral part of the genus Anchisaurus. The complete skeleton of Anchisaurus is on display at the Yale Museum. Several more bones of the same type have been found in South Africa, suggesting that these two land masses once formed a super-continent, Pangea.

Even today, several parts of the Anchisaurus dinosaur skeleton are still untraceable. The reconstructions generally assume that the tail and the neck are like those of the dinosaurs of the same family, the prosauropods. Anchisaurus was quite characteristic of this group and therefore this assumption is probably justified.

Physical appearances

Measuring 6 feet long from head to tail and 8 feet high and weighing around 27 kg (60 lbs), Anchisaurus was not very imposing. It was barely bigger than a sheep. Anchisaurus had a small frail head but had a slender body compared to the general size of the other prosauropods. Its relatively long neck and tail, its powerful hind legs, and its weaker front legs as well as its banana-shaped claw were typical of the peculiarities of the prosauropods. And like almost every animal related to it, Anchisaurus could stand on its hind legs. Nevertheless, it almost always moved on all fours. Its rounded teeth were used to chop the plants it ate.


Anchisaurus would have lived in the New England region at a time when the Atlantic Ocean was just beginning to form. This region was a rift, similar to the Great African Rift that we know today. The hot, humid climate was favorable for the growth of huge fern forests. They offered it plenty of food, but it also allowed it to protect itself from predators. Other small prosauropods, related to Anchisaurus, have been found in Europe and Africa, and it is possible that remnants from Australia and Asia may also have belonged to close relatives.


Anchisaurus was almost certainly herbivorous. Modern paleontologists believe, however, that this dinosaur may have been carnivorous as well, since it is located in a transition zone between two distinct groups. Its teeth were blunt but with leaf-like rims, suggesting a diet consisting mainly of plant material. In addition, the hinge of his jaw was arranged in a way that was not well adapted to the consumption of meat. Nevertheless, the debate still remains. Its thumb was orned with a huge claw and its big eyes were not completely on the sides like animals accustomed to being on the prey side of the food chain. Being in transition between bipedalism and quadripedia, Anchisaurus had flexible front legs. Used as hands, they could be turned inward allowing it to grab. Its first finger was reversible like a thumb. Used as a foot, the five toes could be firmly pressed to the ground and were solidified at the ankle. This non-specific design is typical of early dinosaurs.

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