Sip back as we explore the 41st U.S. State of Montana that has the nickname as the "Treasure State" signifying its abundance in having natural resources, minerals, precious metals as well in its richness for Cretaceous Period dinosaur fossils. Montana’s geology has unlocked many fossils including one of the first nearly complete Tyrannosaurus rex skeletons back in 1902 and Triceratops from the well known Hell Creek Formation. But it’s from the Two Medicine Formation we turn our attention to and the fossil site of Egg Mountain found in the Badlands of Montana on the Willow Creek Anticline near Chouteau. In 1978 the Two Medicine Formation uncovered the bone beds of the large plant eating Hadrosaurid or duck-billed dinosaur called Maiasaura peeblesorum (meaning "good mother lizard") along with a number of nests, eggs, hatchlings, juveniles and adults. Maiasaura peeblesorum was designated as Montana’s State Dinosaur in 1985.
The U.S State of Montana is among the richest fossil locations in the world for Cretaceous Period dinosaurs. They once lived on a vast semi-tropical flood plain with a hot and humid subtropical climate. Today, this fossil location is at the heart of the Rocky Mountain Front where the Rocky Mountains converge with the vast prairies and Big Sky Country.
This is still a landscape that holds all the echoes of the infamous Corps of Discovery Expedition also known as the Lewis and Clark Expedition (1804-1806) following the Louisiana Purchase Treaty where France officially transferred ownership of several territories including Montana to the United States for US $15 million.
Montana's landscape during the Upper Cretaceous Period was vastly different from that of today. During the Upper Cretaceous Epoch Montana was part of a tropical to subtropical environment whose ecosystems featured forests, floodplains, rivers, and deltas that supported a diverse range of dinosaur species.
Many of the dinosaurs lived in low-lying areas near to the rivers and lakes, where flooding was common. When these animals died, their remains were often quickly buried under layers of flooded sediment. This rapid burial reduced decomposition and protected the bones from scavengers setting the scene for fossilisation. Montana’s relatively dry climate today has also helped to preserve exposed fossils and the arid plains and rocky outcrops provide stable environments for fossil to be discovered.
Since the discover of Maiasaura peeblesorum named after the families of John and James Peebles on whose land the fossils were first discovered. A Team of notable researchers including Jack Horner, Holly Woodward, James Farlow, Marion Brandvold and Freedman Fowler et al have used techniques to explore how this dinosaur reproduced and developed.
It is understood that Maiasaura peeblesorum travelled great distances in huge herds in a North-South, and back, direction across the continent of North America following the seasons. Moving as herds provided safety in numbers making it harder for predators to catch a single animal and were sure to have used a "Many-Eyes Theory" where individuals in the herd scanned for predators and spread information quickly.
Migration may have been primarily driven by their food needs as such huge herds of Maiasaura peeblesorum would have required enormous amounts of fresh sources of gymnosperms, such as conifers, cycads, ginkgo and ferns to graze upon.
The fossil record shows that hatchling Maiasaura peeblesorum would weigh about 1Kg and within a 8 to 10 year period they would grow to weigh over 2,000 Kg and reach over 7.5 meters in length. Among the most striking features of female Maiasaura peeblesorum behaviour is believed to be the complex social behaviour of exhibiting parental care in establishing colonial nesting sites to nurture their eggs and protect their hatched young.
The development of Maiasaura peeblesorum is believed to have had six distinct but gradational growth stages including early and late nestling, early and late juvenile, sub-adult, and adult. Interestingly, research also indicates that juveniles walked primarily on two legs before they matured and became much larger where their prominent stance changed to walking on all four limbs.
One of the best ways to experience the dinosaurs of Montana is to visit The Museum of the Rockies in Bozeman MT or get a Prehistoric Passport and travel the Heritage and Cultural Tourism Award winning Montana Dinosaur Trail where you can visit a variety of dinosaur themed exhibits, displays or even book the opportunity to take part in a dinosaur dig.
In Central Montana near to the Willow Creek Anticline the Montana Dinosaur Trail takes in the sites of the Montana Dinosaur Center in Bynum, the Blaine County Museum in Chinook, the Old Trail Museum of Choteau, the Earl Clack Museum in Havre, the Upper Musselshell Museum of Harlowton and the Rudyard Depot Museum.
Along the way you will be introduced to both terrestrial and marine specimens including the full size Seismosaurus halli (meaning “earth-shaker lizard”) measuring 42 meters long and 7 meters tall at the hips as well as the Hadrosaur, Gorgosaurus, Ankylosaurusas, Lambeosaur, Gryposaurus, Avaceratops and marine reptiles of a Mosasaur and Plesiosaur.