Primary Exhibit
Open Year-round

Siebel Dinosaur Complex

Museum of the Rockies (MOR) is a center of active research and exploration into the ancient past. Fossils have been found across much of Montana and the paleontology department at MOR is dedicated to researching the deep past of the state and surrounding regions. Within the museum’s walls is one of the largest collections of North American dinosaurs in the world, including many examples of the gigantic carnivorous Tyrannosaurus rex and a growth series of the horned Triceratops which ranges from juveniles to giants.

Many of these fossils are on display in the museum’s Siebel Dinosaur Complex, where visitors can view Montana’s T.rex, one of the few mounted Tyrannosaurus rex skeletons in the United States, the bones of Big Al, a nearly complete Allosaurus that lived during the Jurassic Period, numerous dinosaur eggs and babies, and more. 

In addition to dinosaurs, the museum contains a large collection of prehistoric mammals that once roamed the state, including mammoths, rhinos, and bone-crushing dogs. These fossils and more are on exhibit in the museum’s Cenozoic Corridor.

Visitors to the museum can see fossil preparators at work in the Bowman Dinosaur Viewing Lab where they carefully remove the rock that has encased fossils for millions of years so that the specimens can be studied. Every day, new discoveries are being made at MOR. 

Each year the paleontology field crew sets off into the rocky outcrops of the Treasure State in order to collect more information about what the world was like millions of years ago and how it and the creatures that have inhabited it have changed through time.

This data-rich exhibit engages visitors in the science of paleontology: how we know what we think we know about dinosaurs. At every turn, you will encounter the latest research on life in the Mesozoic Era, abundantly evident in Montana, as well as the processes of research. Visitors are challenged to formulate their own hypotheses about dinosaur growth, development, behavior, and interactions with their environments. As new discoveries and scientific breakthroughs are made, visitors will see changes in the exhibit.

The Siebel Dinosaur Complex houses the Dinosaurs Under The Big Sky exhibit, one of the largest and most up-to-date dinosaur exhibits in the world. In 2003, Thomas and Stacey Siebel donated $2 million to help triple the museum's dinosaur exhibit space. They were impressed by the museum's user-friendly approach to explaining complex concepts, especially for children. The Siebel Dinosaur Complex was built based on the children's book "Dinosaurs Under the Big Sky" authored by renowned paleontologist and MOR's then Curator of Paleontology Jack Horner, who also contribute to the exhibit's design. 

A new exhibit, Cretaceous Crossroads, will be unveiled within the Siebel Dinosaur Complex in the coming years.

Highlights include:

Did you know that some of the oldest rocks in North America are found in Montana? Travel through 4.6 billion years of Earth’s dynamic prehistory as you begin your journey through time in the Siebel Dinosaur Complex. Walk through the reconstruction of a 2.7 billion-year-old fissure, explore how mountains have risen and seas have spread, and encounter some of the many organisms that evolved in the northern Rocky Mountains region.

Visit the Bowman Dinosaur Viewing Lab and see the process of fossil preparation. Watch MOR volunteer preparators remove rock from around the bones of dinosaurs and other ancient creatures and carefully piece the fossils back together. Preparators are happy to answer your questions and explain how they ready these specimens for study. The lab is active seven days a week between the hours of 9 a.m. – 5 p.m.

How do fossils get to a museum? Explore the process of paleontology, from the small fragments of bone that first reveal that a dinosaur skeleton is nearby, through the collection, preparation, curation, and study of the creatures found in the Siebel Dinosaur Complex. This vantage point provides an overview of the skeleton of Big Al and the other inhabitants of the Hall of Giants.

A staircase located adjacent to the Bowman Dinosaur Viewing Laboratory will lead you up to the Overlook. Alternate access to the Overlook can be achieved via elevator by inquiring at the Front Desk.

Begin your journey through the Age of Dinosaurs in the Hall of Giants. Enter the Jurassic Period and encounter ‘Big Al’, one of the most complete Allosaurus ever discovered. This Jurassic carnivore’s skeleton records evidence of a hard life, including injuries and infections.

As you enter the Cretaceous Period, you will meet Deinonychus. The discovery of this relative of Velociraptor helped cement the link between ancient dinosaurs and modern birds.

As the tides change, dip under the surface of the seaway that covered much of North America during the Cretaceous, and keep an eye out for carnivorous marine reptiles.

Then, peek inside the lair of Oryctodromeus, the first dinosaur discovered inside a burrow.

The world of Maiasaura, the state fossil of Montana, is brought to life through the original artwork of paleoartist Douglas Henderson.

These classic pieces, in pastel, graphite, and gouache, depict what life may have been like 76 million years ago, near the site known as Egg Mountain.

Much of the art in this exhibit was made for the book Maia: A Dinosaur Grows Up by Jack Horner and James Gorman.

Even giant dinosaurs started off as tiny babies. View spectacular examples of dinosaur eggs, embryos, and hatchlings in the Hall of Growth and Behavior.

Learn how paleontologists can look inside the bones of dinosaurs to understand how they grew.

Examine how the skulls of some dinosaurs changed as they aged, including Daspletosaurus horneri, a relative of T. rex that lived about 10 million years earlier, the crested duck-billed dinosaur Hypacrosaurus, and the horned dinosaur Achelousaurus.

While dinosaurs roamed the land, different creatures inhabited a vast seaway that covered much of this region. Come face to face with Mosasaurus, a large carnivorous marine lizard that lurked off the shore in the Cretaceous.

This hall was made possible by a gift from Paulena, Max, Gus, & Gideon Prager.

Enter the world of the Hell Creek Formation and meet some of the last non-avian dinosaurs to roam Montana, includingTriceratops and Tyrannosaurus rex!

  • Tyrant Kings - Come face to face with a world-class T. rex fossil collection including the largest and smallest skulls ever discovered! Explore what this famous dinosaur ate and how it lived. Tyrannosaurus rex, meaning “tyrant lizard king,” roamed the earth 65 million years ago. Now among only a handful of museums in the world to display a fossilized T. rex skeleton, this exhibit presents one of the most spectacular specimens ever unearthed called Montana’s T. rex. Discovered near the Fort Peck Dam and one of the most complete T. rex skeletons ever found, Montana’s T. rex stands 12 feet tall and approximately 40 feet from nose to tail. It would have weighed almost seven tons as it walked the eastern regions of the state. The Tyrant Kings, featuring Montana’s T. rex presents the science and research of Tyrannosaurus rex in a very, very big way.
  • Triceratops – Grow up with Triceratops as one of the largest collections of this famous three-horned giant reveals how this animal grew and evolved. From baby to behemoth, learn how MOR’s Triceratops discoveries have shed light on dinosaur biology, growth, and diversity. See Triceratops develop from baby to adult in a series of skulls, ending with one of the largest dinosaur skulls ever discovered! Skeletons of an adult and a juvenile Triceratops pace warily near Montana’s T. rex, and a tyrannosaur-bitten hip bone shows what happened when these animals got too close!

Sixty-six million years ago, a mass extinction event ended the reign of the non-avian dinosaurs and brought the Mesozoic Era to an end. This marked the beginning of the Cenozoic Era, a time when mammals, a group of animals that had lived in the shadows of the dinosaurs for over 100 million years, came to dominate the Earth.

The Cenozoic Corridor highlights the fossils of mammals and other creatures that roamed Montana after the ‘Age of Reptiles’, including ancient horses, bison, mammoth, rhinoceros, and a bone-crushing dog.