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Anchisaurus

Anchisaurus is a genus of dinosaurs.

Discovery

The first discovery of Anchisaurus ("near lizard") leftovers was made before anything was known about the dinosaurs, and it was almost certainly the first dinosaur discovery in North America. When, in 1818, some large bones were discovered in Connecticut, USA, it was unspecified that they were of human origin. Gradually, as a result of further finds in Massachusetts, the number of these bones began to accumulate and by 1855 they were at least recognized as reptilian. Hitchcock collected these bones under the name "Megadactylus" in 1865. The great paleontologist Othniel Charles Marsh named Anchisaurus in 1885, and Megadactylus become part of the genus Anchisaurus. More bones belonging to the genus were found in South Africa, suggesting that those two landmasses were at the time joined in one super-continent (Pangaea). A revival from Nova Scotia may also be Anchisaurus but this is unconfirmed.

Today, parts of Anchisaurus' skeleton are still missing. Reconstructions typically assume that the tail and neck are like that of other dinosaurs of the same family, prosauropods. Anchisaurus was quite characteristic of this group and so this assumption is probably justified. Description In order to have been wrong for human bones, one would expect Anchisaurus to be a rather small dinosaur - and, with a length of just over 2 meters, indeed it was. It most likely weighed around 27 kg. However, Marsh's species A. major was larger, from 2.5 m up to 4 m, and some estimates give it a weight of up to 70 kg. All species lived through the late Jurassic era; more specifically, the Pliensbachian to Toarcian periods, 200 to 188 million years ago.

Digesting plant matter is a much more concentrated biochemical process than digesting meat, and so herbivorous dinosaurs needed a huge gut. Since this had to be positioned in front of the pelvis, complementary on two legs became increasingly tricky, and they gradually evolved into the quadripedal position that characterizes the later sauropods such as Diplodocus. Prosauropods, then, represented a center phase between the earliest bipedal herbivores, and the later giant sauropods. Anchisaurus was characteristic of this group that flourished briefly during the late Triassic and Jurassic. It would have spent most of its time on four legs, but could have risen up on its hind legs to reach higher plants.

On the new hand, paleontologists believe Anchisaurus may also have eaten meat, as it was in the transition between these two ultimately separate groups. The teeth were blunt but with file-like edges, suggesting mostly plant matter was eaten, and the jaw hinge was set in a way not entirely suited for tearing meat. Nevertheless, there is still some debate. The thumb had a huge claw, and the large eyes were not entirely on the side (as would be expected in an animal used to being prey).

As a quadropedal/bipedal crossover, Anchisaurus had to have flexible front legs. As hands, they could be turned inwards and be used for grasping. It had a simple reversible first finger, similar to a thumb. As feet, the five toes could be located flat against the floor and were strong at the ankle. This unspecialized design is typical of the early dinosaurs.

Classification

Order: Saurischia
Suborder: Sauropodomorpha
Infraorder: Prosauropoda
Family: Anchisauridae
Genus: Anchisaurus
Anchisaurus is sometimes known as Yaleosaurus, due to Huene (1932).

Marsh was initially happy with Hitchcock's name Megadactylus, but this name was already taken. Therefore, he renamed it Amphisropoda
Family: Anchisauridae
Genus: Anchisaurus
Anchisaurus is sometimes known as Yaleosaurus, due to Huene (1932).

Marsh was initially happy with Hitchcock's name Megadactylus, but this name was already taken. Therefore, he renamed it Amphisaurus in 1882. However, this name was also worried! Therefore, it became Anchisaurus in 1885.

The type species is Hitchcock's A. polyzelus. Marsh's A. major ("greater near lizard") is still measured among the Anchisaurs. However, his A. colurus of 1891 is now generally established as a female A. polyzelus, and his A. solus of 1892 is now reclassified as Ammosaurus major. However, Ammosaurus itself may well be a synonym of A. polyzelus. Broom named "Gyposaurus" in 1911, from the bones exposed in South Africa, but Peter Galton officially named it A. capensis in 1971. This genus has since been reclassified again, and is now Massospondylus carinatus. Other specimens are still pending reclassification. This confusion is typical of the first dinosaurs to be exposed, when classification was not considered such a significant process.