What is the Morrison formation?

The world-famous Morrison formation is a specific layer of sedimentary rock made up of deposits of sand, mud, and volcanic ash. It formed approximately 141 to 156 million years ago during the Late Jurassic period. This rock is one of the richest dinosaur fossil spots in the United States, usually yielding excellent specimens. It was first discovered near Morrison, Colorado, in the late 1800s hence its name.

What Colorado sites have been historically fruitful in terms dinosaurs finds?

Colorado contains four major historically significant dinosaur sites, especially in terms of the nature and number of finds. These sites are Dinosaur Ridge, Garden Park, the Grand Junction area, and Dinosaur National Monument. The reason for the success of these areas, and others in Colorado, is the presence of exposed rocks from the Morrison formation of the Jurassic period.

What is Dinosaur Ridge?

Dinosaur Ridge is composed mostly of rock from the Morrison formation. It is located north of the town of Morrison, just west of Denver, Colorado. This site was first discovered in 1877 by Arthur Lakes (1844-1917) and was subsequently excavated during the great Bone Wars; the fossil site was worked by Othniel Charles Marsh (1831-1899) and his crew.

The Yampa and Green Rivers meet at Steamboat Rock in Colorados Dinosaur National Monument. This area has proven to be rich in dinosaur fossils (Big Stock Photo).

What is the significance of the Hogback Ridge on the Colorado and Utah border?

Originally, from 1909 to 1922, the Hogback Ridge at Split Mountain was worked by American paleontologist Earl Douglass (1862-1931) for the Carnegie Museum (the site was called the Carnegie Quarry). On October 4, 1915, President Woodrow Wilson designated the spot as Dinosaur National Monument because of its importance to paleontology and to stop any future development of the area.

In 1909, Douglass found the dorsal bones of an Apatosaurus at this site; it took six more years to remove the skeleton from the rock and mount it at the Carnegie Museum. After 1922, Douglass worked the quarry for two more years (for the University of Utah and the Smithsonian Institution) finding a Diplodocus that is currently mounted at the Smithsonian. Today, tourists at the visitors center at Hogback Ridge can view the quarry face that acts as the north wall of the building; the bones were left in place after the overlying rocks were removed.

Where and what is Como Bluff?

Como Bluff is a long, east-west oriented ridge located in southern Wyoming. It is also the site of a famous Jurassic dinosaur fossil bed excavated during the great Bone Wars of the late 1800s. It was discovered by two employees of the Union Pacific Railway, W.E. Carlin and Bill Reed, as a new rail line was being built through the general area. They secretly contacted Othniel Charles Marsh (1831-1899), trying to sell him some gigantic bones. Marsh subsequently sent his assistant S.W. Williston (1851-1918) to investigate the situation. Williston informed Marsh that the bones extend for seven miles and are by the ton.... The bones are very thick, well preserved, and easy to get out. Because of Willistons words, Marsh hired Carlin and Reed to work the beds exclusively for him and to send the fossil bones back to Yale University. From samples of bones uncovered at Como Bluff, Marsh named the dinosaurs Stegosaurus, Allosaurus, Nanosaurus, Camptosaurus, and Brontosaurus (now known to be the same animal as Apatosaurus). Excavations at Como Bluff were discontinued after 1889.

When was the first complete fossil skeleton of a Stegosaurus found in the United States?

In 1886, near Canyon City, Colorado, the fossilized remains of a Stegosaurus were found by Othniel Charles Marshs crew. The animals dorsal armor plates were arranged in two rows along the back, with the plates alternating position. This skeleton was subsequently displayed in the Smithsonian Institution in Washington, D.C., exactly as it was found in the field.

Where is the largest known collection of theropod skeletons in the world?

The largest mass accumulation of theropod skeletons in the world was found at the Ghost Ranch quarry in northwestern New Mexico. In 1947, George Whitaker and Edwin Harris Colbert (1905-2001), members of an expedition from the American Museum of Natural History, found over 100 skeletons of the Late Triassic period dinosaur Coelophysis. They found the dinosaur skeletons in Arroyo Seco (Dry Canyon) on the lands of the Ghost Ranch.

There are a number of sites aroudn the world considered to be fossil parks, places rich in large collections of dinosaur fossils (iStock).

The skulls in this bone bed show considerable variations in size, ranging from 3 to 10 inches (8 to 26 centimeters) in length, indicating the presence of both juveniles and adults. In 1948, during further excavations, George Whitaker and Carl Sorenson discovered two skeletons of Coelophysis with juveniles inside the stomach areas. This was thought to indicate that this species was cannibalistic.

It is still a mystery why so many of these animals ended up in such a small area.

Some paleontologists suggest that a herd of Coelophysis was overwhelmed by a flood, perhaps while crossing a river. If this is true, then this discovery is the first evidence for herding behavior among a dinosaur species.

When was the first Triceratops fossil discovered in the United States?

A fossilized skull of a three-horned, Cretaceous period, herbivorous dinosaur was discovered by John Bell Hatcher (1861-1904) and Othniel Charles Marsh (1831-1899) in 1888 in the Judith River beds of Montana. This dinosaur would subsequently be named Triceratops.

When was the first Tyrannosaurus rex fossil discovered in the United States?

The first Tyrannosaurus rex skeleton was discovered in the United States in 1902 by Barnum Brown (1873-1963), who was perhaps the greatest collector of dinosaur fossils. Brown, working for the American Museum of Natural History, discovered the remains in the area of Hell Creek, Montana.

Where was the first known fossilized dinosaur skin found in the United States?

In 1908, the fossil impression of a duck-billed dinosaurs skin was discovered in Wyoming by paleontologist Charles H. Sternberg (1850-1943) and his three sons: Charles M., George, and Levi Sternberg.

Where was an almost complete skeleton of an Apatosaurus (formerly known as a Brontosaurus) found in the United States?

In 1909, American paleontologist Earl Douglass (1862-1931) discovered an Apatosaurus skeleton in the Carnegie Quarry (now Dinosaur National Monument) on the border between Utah and Colorado. Through 1923, further excavations in this area uncovered the largest known concentration of Jurassic period dinosaurs in the United States.

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