| Jurassic National Monument | |
|---|---|
 Cleveland-Lloyd Dinosaur Quarry Visitor Center | |
  Map ofUtah | |
| Location | Emery County,Utah |
| Nearest city | Cleveland |
| Coordinates | 39°19′22″N110°41′22″W / 39.32282°N 110.68951°W /39.32282; -110.68951 |
| Governing body | Bureau of Land Management |
| www | |
| Designated | 1965 |
Jurassic National Monument, at the site of theCleveland-Lloyd Dinosaur Quarry, well known for containing the densest concentration ofJurassicdinosaur fossils ever found, is a paleontological site located nearCleveland, Utah, in theSan Rafael Swell, a part of thegeological layers known as theMorrison Formation.
Well over 15,000 bones have been excavated from this Jurassic excavation site and there are many thousands more awaiting excavation and study. It was designated aNational Natural Landmark in October 1965.[1] TheJohn D. Dingell Jr. Conservation, Management, and Recreation Act, signed into law by President Donald Trump on March 12, 2019, named it as anational monument.[2]
All of these bones, belonging to different species, are found disarticulated and indistinctly mixed together. It was hypothesized byPeter Dodson in 1980 that this strong concentration of mixed fossilized bones was due to a "predator trap", however it is more likely that this site was actually caused by an extreme drought.[3][4] No strictscientific consensus currently exists.
The visitor center is administered by theBureau of Land Management. There is a skeleton reconstruction of an adultAllosaurus (and other bones) on display in the visitor center, along with many other exhibits. A renovated and expanded quarry visitor center was dedicated on April 28, 2007. The visitor center is open seasonally with variable hours.
The quarry was found by sheepherders and cattlemen as they drove their animals through the area during the late 19th century. In 1927, the Department of Geology at theUniversity of Utah, under the direction of Chairman F.F. Hintze, visited the area and collected 800 bones. In 1939-41 a field party ofPrinceton University, led byWilliam Lee Stokes (1915–1994, known as the "Father of Utah geology"), came on site to extensively dig up specimens. Because of the proximity to Cleveland, Utah, and because these expeditions were financed by Malcolm Lloyd, the site was later known as the Cleveland-Lloyd Quarry.[5] In three summers, the 1939-1941 Princeton expeditions collected 1,200 bones. A part of these bones was sent toPrinceton and eventually the bones were sorted to mount a complete composite skeleton ofAllosaurus, but World War II broke out and the skeleton was not mounted and exhibited in the university until February 1961. ThisAllosaurus skeleton,still nowadays on display at Guyot Hall, in the campus of New Jersey, is most likely the firstAllosaurus skeletal mount obtained from the quarry. In the meantime, and because excavations had been interrupted by the war, work started again in 1960, when young paleontologistJames Henry Madsen Jr. (1932–2009) was hired within the University of Utah to assist William Lee Stokes with the excavations.
As of 1960 Stokes and Madsen founded the "University of Utah Cooperative Dinosaur Project",[6] with funds of the University of Utah. This project granted casts or specimens of dinosaurs to museums and institutions from the US but also from countries all around the world, in exchange of financial and excavation assistance.[6] The project continued until 1976 when the University of Utah interrupted the funding. Madsen managed to continue excavating the quarry by means of a private company he founded the same year, Dinolab, intended to sell casts of dinosaur skeletons to museums, institutions and private buyers. Before that, in 1974, a new dinosaur had been described by Madsen, then assistant research professor ofgeology andgeophysics in the University of Utah. He named itStokesosaurus clevelandi, honoring his mentor, professor William Lee Stokes. In 1976, another new dinosaur was described from fossils found in the quarry by Madsen. He named itMarshosaurus bicentesimus, honoring American paleontologistOthniel Charles Marsh (1831–1899). In 1987,Brigham Young University paleontologists excavated a fossil dinosaur egg, at the time the oldest such egg ever found.
Over the years, excavations led by the University of Utah and theNatural History Museum of Utah have resulted in the collection of more than 12,000 fossil bones from the quarry. While most of the original fossils are currently housed at the Natural History Museum of Utah, many skeletons reproduced from Cleveland-Lloyd dinosaur remains are now on exhibit in more than 65 museums worldwide. Original specimens from the quarry remain on public exhibit in Utah at the Natural History Museum of Utah inSalt Lake City, theUtah State University Eastern Prehistoric Museum[7] inPrice and the Earth Science Museum atBrigham Young University inProvo.
The U.S. Department of the Interior,Bureau of Land Management (BLM) opened a visitor center at the Cleveland-Lloyd Dinosaur Quarry in 1968. This was the first-ever BLM visitor center. On April 28, 2007, a new, larger facility was dedicated that has updated exhibits. The new visitor center generates its own electricity from rooftop solar panels.
Early in 2019, the quarry reached the official status of "national monument" under the name of "Jurassic National Monument".[8][9]
The Cleveland-Lloyd Dinosaur Quarry of east central Utah has produced one of the most prolific dinosaurs bone assemblages in the Upper Jurassic beds of North America. The quarry is part of the Brushy Basin Member of theMorrison Formation. The fossil deposit consists of acalcareoussmectiticmudstone which accumulated on the floodplain of an anastomosing river system. Ananastomosing river system consists of multiple interconnected channels confined by prominentlevees separated by interchannel topographic lows. The depositional environment of the quarrymudstone was an interchannel seasonal accumulation of clay nested in a topographic low between channel levees called a floodpond.
Dinosaurs came to the floodpond during a drought in search of water, with the herbivores and smaller carnivores falling prey to the largetheropods present for food. As the drought continued, the dinosaurs present dwindled until eventually adultAllosaurus would resort to cannibalizing juvenile individuals for survival. The preserved fauna consists of almost all dinosaurs with the majority being carnivorous dinosaurs includingAllosaurus (material from at least 44 individuals make up almost 67% of all remains),Torvosaurus (1),Ceratosaurus (1),Stokesosaurus (2),Marshosaurus (2), and aTanycolagreus (1). Herbivorous dinosaurs includeCamarasaurus (3),Diplodocus (1),Barosaurus (1),Apatosaurus (1),Camptosaurus (5), andStegosaurus (4).[10] Non-dinosaurian fauna include a crocodile (Goniopholis), 2 turtles (Glyptops), 4 genera of gastropoda (snails), and 4 genera of charophyte.
For a long time, the atypical predator/prey ratio (3:1) represented at the quarry was thought to be the result of possible pack hunting tendencies ofAllosaurus. The high percentage of smaller individual allosaurs suggests that juveniles coordinated their efforts to capture and kill prey. They may have followed their prey into the floodpond and subsequently became mired themselves. The close spatial proximity of skull elements (most belonging toAllosaurus) seemingly supported this hypothesis. Larger individual theropods almost certainly became mired while attempting to scavenge the carcasses of other entrapped dinosaurs (Richmond and Morris, 1996). However, more recent studies suggest that the mass deaths were in fact a result of a drought, and not a predator trap.[3] One comparison with theLa Brea Tar Pits suggests that multiple, non-migratory groups ofAllosaurus may have come to the area looking to find water, dying due to the harsh conditions and perhaps from diseases caused by drinking contaminated water due to rotting carcasses and feces being present. The evidence for this theory is strengthened by the fact that a large proportion of theAllosaurus specimens are juveniles, but until more evidence is recovered, this cannot yet be vindicated.[4]
Fossil taxa discovered at the Cleveland-Lloyd site include:
Color key
| Notes Uncertain or tentative taxa are insmall text; |
| Ornithischians reported from the Cleveland-Lloyd Quarry | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Notes | Images | |||
C. dispar |  | |||||
S. stenops | The largestornithischian reported from the quarry | |||||
| Sauropods reported from the Cleveland-Lloyd Quarry | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Notes | Images | |||
A. sp |   | |||||
B. sp | ||||||
C. lentus | 3 skeletons were unearthed | |||||
D. sp | ||||||
| Theropods reported from the Cleveland-Lloyd Quarry | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Amount | Notes | Images | ||
A. fragilis | 44 - 60 | The largesttheropod reported from the quarry |   | |||
C. dentisulcatus (may just represent the adult form ofC. nasicornis) | 1 | The raresttheropod species in the quarry | ||||
M. bicentesimus | 2 | |||||
S. clevelandi | 2 | The largestcoelurosaur reported from the quarry | ||||
T. topwilsoni | 1 | Remains originally referred toStokesosaurus clevelandi. | ||||
T. tanneri | 1 | |||||
Year designated: 1965
