Jurassic National Monument

The visitor center is administered by the Bureau of Land Management. There is a skeleton reconstruction of an adult Allosaurus (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. ==History==

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 the University of Utah, under the direction of Chairman F.F. Hintze, visited the area and collected 800 bones. In 1939-41 a field party of Princeton University, led by William 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. In three summers, the 1939-1941 Princeton expeditions collected 1,200 bones. A part of these bones was sent to Princeton and eventually the bones were sorted to mount a complete composite skeleton of Allosaurus, but World War II broke out and the skeleton was not mounted and exhibited in the university until February 1961. This Allosaurus skeleton, still nowadays on display at Guyot Hall, in the campus of New Jersey, is most likely the first Allosaurus 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 paleontologist James 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", in Price and the Earth Science Museum at Brigham Young University in Provo. 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". ==Geology==

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 the Morrison Formation. The fossil deposit consists of a calcareous smectitic mudstone which accumulated on the floodplain of an anastomosing river system. An anastomosing river system consists of multiple interconnected channels confined by prominent levees separated by interchannel topographic lows. The depositional environment of the quarry mudstone 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 large theropods present for food. As the drought continued, the dinosaurs present dwindled until eventually adult Allosaurus would resort to cannibalizing juvenile individuals for survival. The preserved fauna consists of almost all dinosaurs with the majority being carnivorous dinosaurs including Allosaurus (material from at least 44 individuals make up almost 67% of all remains), Torvosaurus (1), Ceratosaurus (1), Stokesosaurus (2), Marshosaurus (2), and a Tanycolagreus (1). Herbivorous dinosaurs include Camarasaurus (3), Diplodocus (1), Barosaurus (1), Apatosaurus (1), Camptosaurus (5), and Stegosaurus (4). 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 of Allosaurus. 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 to Allosaurus) 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. One comparison with the La Brea Tar Pits suggests that multiple, non-migratory groups of Allosaurus 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 the Allosaurus specimens are juveniles, but until more evidence is recovered, this cannot yet be vindicated. ==Paleobiota==

Fossil taxa discovered at the Cleveland-Lloyd site include: ===Plantae=== • Thallophyta • Aclistochara • Latochara • Stellatochara ===Mollusca=== ====Gastropoda==== • Amplovalvata • Amplovoluta • Valvata • Viviparus ===Chelonii=== • Glyptops ===Dinosauria=== Ornithischians Sauropods Theropods ==See also==

• Stokes, William J. (1945). A new quarry for Jurassic dinosaurs. Science. 101 (2614): 115–117. Bibcode:1945Sci...101..115S • Stokes, W. L. (1985). The Cleveland-Lloyd Dinosaur Quarry: Window to the Past. U. S. Government Printing Office. • Richmond, D. R. and Morris, T. H. (1996). The dinosaur death trap of the Cleveland-Lloyd Dinosaur Quarry, Emery County, Utah, in Morales, M., ed., The Continental Jurassic: Museum of Northern Arizona Bulletin 60, pp. 533–545. • Joseph E. Peterson, Jonathan P. Warnock, Shawn L. Eberhart, Steven R. Clawson & Christopher R. Noto (2017). New data towards the development of a comprehensive taphonomic framework for the Late Jurassic Cleveland-Lloyd Dinosaur Quarry, Central Utah. PeerJ 5:e3368, doi: http://doi.org/10.7717/peerj.3368 • Hunt, Adrian P; Lucas, Spencer G.; Krainer, Karl; Spielmann, Justin (2006). The taphonomy of the Cleveland-Lloyd Dinosaur Quarry, Upper Jurassic Morrison Formation, Utah: a re-evaluation. In Foster, John R.; Lucas, Spencer G. Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin, 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 57–65. • Loewen, Mark A. (2003). Morphology, taxonomy, and stratigraphy of Allosaurus from the Upper Jurassic Morrison Formation. Journal of Vertebrate Paleontology. 23 (3, Suppl.): 72A. doi:10.1080/02724634.2003.10010538 ==Further reading==