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Tyrannosaurus Rex


It was about this time in 1905 that H. F. Osborn revealed the discovery of the “Dynamosaurus” or “dynamic lizard.” Now known as the Tyrannosaurus, or T. rex, this nasty carnivore literally surfaced for the first time just across the border in Montana.

The discovery was in what’s known as the Hell Creek Formation, which is visible in quite a few locations; in addition to areas of Montana, it also occurs in North and South Dakota, and a few other spots under different names. In North Dakota, the Hell Creek Formation is about 300 feet thick in western ND and about 150 feet thick in the Bismarck area.

As you may remember, a sub-tropical sea covered a great deal of ND 65 million years ago. Feeder rivers flowing east from the Rocky Mountain area created huge silt deposits the size of today’s Mississippi Delta on the west side of the sea.

ND Paleontologist John Hoganson writes, “This delta was teaming with life, including T. rex and about 10 other kinds of dinosaurs, several other kinds of creatures like crocodiles, turtles, fish, salamanders – even small mammals. We know this because we find fossils of these animals in the Hell Creek rocks in ND. There were also exotic plants growing here at that time, including palm trees. It was hot and humid, a great place for reptiles like T. rex and humans drinking pina coladas.”

The word Tyrannosaurus translates to “tyrant reptile.” As someone aptly said, the Tyrannosaurus was “the most terrifying engine of destruction ever to have walked the earth.” At about 40' long and roughly 20' tall, it weighed around eight tons – more than a modern African bull elephant. Its head alone was more than four feet long, and its jaws were lined with 60 six-inch teeth. Because its head was so large, it’s neck was short, thick and powerful, and it used its tail as a counterbalance. Support came from monolithic hind-legs ending in three-toed feet tipped with long sharp talons. In stark contrast were its very small forelimbs and tiny two-clawed hands.

Paleontologist Dean Pearson discovered the first Tyrannosaurus in North Dakota. It’s the largest collection of T. rex bones yet to be found in this state. Due, in part, to his discovery, Pearson was given the Harrell L. Strimple Award in 2001 – at 43, he was the youngest person to ever win this honor. Pearson and others excavated the bones in the southwest part of the state, and they are now displayed at the Pioneer Trails Regional Museum in Bowman.

Based on research conducted by Hoganson and others, the farthest east the T. rex lived in North America was near Bismarck. Hoganson says scientists have found T. rex remains in about six spots south of Bismarck and Mandan and several in the Marmarth area. In almost all these areas, only a few parts of the animal have been found, mostly teeth.

At least 14 partial skeletons have been found at different sites, but nobody has yet found an entire skeleton. That doesn’t mean others sites haven’t been discovered, however. Some fossils are dug and sold commercially, sometimes going unreported. Others are collected and taken from the state illegally, which is a major concern for scientists.

Here’s the scoop on digging for fossils: a permit is required to dig on public or government-owned land. It’s legal to dig for fossils on private land with the landowner's permission, but any fossil found on private land belongs to the landowner, unless other arrangements are made ahead of time.

Sources: Johnson, Kirk R. Presentation of the Harrell L. Strimple Award to Dean Pearson / Response by Dean Pearson. Journal of Paleontology. July, 2001.

Osborn, H. F. 1905. Tyrannosaurus and other Cretaceous carnivorous dinosaurs. Bulletin of the American Museum of Natural History 21: 259-265.

Hoganson, John. Written correspondence, 2005.

Cataldo, Rosie. Digging for dollars: Ninth District dinosaurs still have an (economic) impact. Fedgazette. July 2001

Dakota Datebook written by Merry Helm