Allosaurus

About the Museon Allosaurus fossil

The Museon Allosaurus is 8 metres long and its height at the head is 3.30 metres. At the hips, the height is 2.70 metres. The Allosaurus was found on the territory of a private ranch on the border of Utah and Wyoming (United States), 30 kilometres east of the city Jensen.

Almost complete
When the Museon Allosaurus was found, it was nearly  complete. Lacking were only a lower jaw half, some parts of the legs, a small quantity of ribs and projections from a number of vertebrae which are only seldom preserved. To complete our Allosaurus, we used casts from another Allosaurus. The rest of the Allosaurus, including all teeth, is completely original.

From discovery to skeleton
Preparing the skeleton was an immense task. For example, the pelvis had to be freed from rock-hard sandstone. Here, the problem was the fact that the fossil material was nearly as hard as the rock from which the bones were to be released. In such a case, it is very difficult to determine the boundary between  bone and stone, so releasing the bones will take a lot of time. The cervical vertebrae were hidden in slate. This caused other problems in releasing them, namely, that the vertebrae had been deformed considerably. The preparator has managed to reconstruct them magnificently and has created a slightly S-shaped neck. This shape is known from reconstructions made earlier . The Allosaurus has been displayed in an active position, as if the skeleton is walking.

Brown
The skeleton is mainly brown, due to ferric oxide (rust) present.  The fossil material shows  whitish spots as well. These spots were probably created by an unknown mineral that has dissolved part of the ferric oxide during disintegration, allowing the spots to arise. 

Where was the Allosaurus found?
The Museon Allosaurus was found in the world-famous Morrison Formation. This is a sediment that was formed in the central part of the United States between 155 and 148 million years ago. The Morrison Formation covers a surface of 1.5 million km². These sediments have been formed in an era when the climate was much warmer than it is today. A subtropical climate prevailed up to 60° north latitude (now the south points of Greenland and Finland). There are indications that there were dry seasons as well.

In the southern part of the Morrison Formation, there are sandstones that were formed as dunes in a desert. To the north, the Morrison Formation is comprised of sediments that were deposited by meandering rivers. They have left traces in the form of sandy midstreams. The Allosaurus was found in these river sediments.

 

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