Dakota (fossil)

Dakota is the nickname given to a fossil Edmontosaurus annectens found in the Hell Creek Formation in North Dakota. It is about 67 million years old, placing it in the Maastrichtian, the last stage of the Cretaceous period. It was about 11 m (35 ft) long and weighed about 3.5 tons.

The fossil is unusual and scientifically valuable because soft tissue including skin and muscle have been fossilized, giving researchers the rare opportunity to study more than bones, as with most vertebrate fossils. Preliminary research results indicate that hadrosaurs had heavier tails and were able to run faster than was previously thought.

Dinosaur fossils with Dakota's degree of preservation are extremely rare because many different factors must come together to allow it to occur. The carcass first must escape scavengers as well as degradation by the elements. The soft tissue must then be mineralized before it decomposes. Finally, as with all fossils, the mineralized body must escape destruction by geological forces over millions of years.

News reports have referred to Dakota as "mummified"; however, it is actually a fossil of a mummified dinosaur, where the animal's dried tissues have been transformed to rock through fossilization.

Dakota was first discovered by paleontology student Tyler Lyson on his family's North Dakota property in 1999 while he was a high school student, but he did not investigate the site in detail until 2004, when he discovered the soft tissue preservation. Lyson teamed with British paleontologist Phillip Manning, and the site was excavated in summer 2006.

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