The Dry Mesa Dinosaur Quarry is situated in southwestern Colorado, United States, near the town of Delta. Its geology forms a part of the Morrison Formation and has famously yielded a great diversity of animal remains from the Jurassic Period, among them Ceratosaurus , Supersaurus , and Torvosaurus . The quarry is found within the Uncompahgre National Forest.
In 1971, a large theropod phalanx ( Torvosaurus tanneri [1] ) was discovered at Dry Mesa by Ed and Vivian Jones [2] of Delta, Colorado. The find was reported to James A. Jensen [3] of Brigham Young University (BYU) who commenced quarrying operations in 1972. In 1973, Brigham Young University cooperated with producer Steve Linton and director John Linton in order to produce The Great Dinosaur Discovery , a 1-hour-long color documentary showing Jensen's on-site finds in Dry Mesa. First released on November 13, 1973, in local "Egyptian Theater" in Delta, and subsequently aired on several USA TV channels, The Great Dinosaur Discovery was originally planned to be trimmed to about 30 minutes for educational use. [4] Indeed, to obtain a shortened educational version, the full-length documentary was reduced to a 24-minute-long mini-film which started airing on American television channels throughout the USA as of 1976.
During the four years that spanned from 1972 to 1976, rocks and fossils were stocked at the BYU football stadium until a specific building was constructed in 1976 for the BYU Earth Science Museum, [5] known in the present day as the BYU Museum of Paleontology. Under the direction of the BYU Earth Science Museum, the quarry has been excavated for 13 field seasons. Approximately 4000 bones have been collected, making it one of the most prolific dinosaur producing accumulations in the Morrison Formation. Thirty vertebrate genera are represented in the quarry including dinosaurs, a pterosaur, crocodile, turtle, lungfish, and a prototherian mammal. Twenty-three genera of dinosaurs have been found in the quarry distinguishing it as the most diverse Jurassic dinosaur assemblage. The quarry is especially recognized for its large sauropods, among which Supersaurus vivianae [6] and Ultrasauros macintoshi [7] are the most celebrated finds (Richmond and Morris, 1999).
The Dry Mesa Dinosaur Quarry of western Colorado yields one of the most diverse Upper Jurassic vertebrate assemblages in the world. This fossil assemblage was deposited within a poorly sorted sandstone bed that is stratigraphically situated in the lower portion of the upper Brushy Basin Member of the Morrison Formation. The bone accumulation, consisting of thousands of bones, was the consequence of two cataclysmic events, a drought, and flash flood. In the Dry Mesa area, a severe drought resulted in the mass mortality of dinosaurs and other vertebrates. These animals were attracted to a remnant water hole of the dry Lake T'oo'dichi' lake bed where they died of starvation and dehydration. This mass mortality produced a considerable accumulation of disarticulated vertebrate remains. Subsequently, a short-lived flash flood traversed the dry lake beds. The quarry sandstone bed is a 2 meter thick, 121 meter wide, very poorly sorted pebble-rich sublitharenite. The channel sandstone shows abundant trough cross-stratification and a possible antidune bedform composed of gravel and sand which indicates flow velocities as high as 200 cm/s (5 miles/hour). Measured bone volumes can be equated to flow velocities. These calculated bone volume velocities are in agreement with flow velocities determined from grain size and bedforms. The river flow direction, based upon bedform orientations and bone elongation statistics, was to the east-northeast. Geologic and taphonomic characteristics indicate a short transport distance for the bone accumulation (Richmond and Morris, 1999).
Allosaurus is an extinct genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period. The name "Allosaurus" means "different lizard", alluding to its unique concave vertebrae. It is derived from the Greek words ἄλλος and σαῦρος. The first fossil remains that could definitively be ascribed to this genus were described in 1877 by famed paleontologist Othniel Charles Marsh. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of paleontological circles.
Supersaurus is a genus of diplodocid sauropod dinosaur that lived in North America during the Late Jurassic period. The type species, S. vivianae, was first discovered by Vivian Jones of Delta, Colorado, in the middle Morrison Formation of Colorado in 1972. The fossil remains came from the Brushy Basin Member of the formation, dating between 153 to 145 million years ago. It was a very large sauropod, with the WDC and BYU specimens reaching 33–35 meters (108–115 ft) in length and approximately 35–40 metric tons in body mass. A potential second species, S. lourinhanensis (Dinheirosaurus), is known from Portugal and has been dated to a similar time.
Ultrasaurus is a genus of sauropod dinosaur discovered by Haang Mook Kim in South Korea. However, the name was first used unofficially in 1979 by Jim Jensen to describe a set of giant dinosaur bones he discovered in the United States. Because Kim published the name for his specimen before Jensen could do so officially, Jensen renamed his specimen Ultrasauros. Jensen's giant sauropod was later found to be a chimera, and the type remains are now assigned to Supersaurus.
Ceratosaurus was a carnivorous theropod dinosaur that lived in the Late Jurassic period. The genus was first described in 1884 by American paleontologist Othniel Charles Marsh based on a nearly complete skeleton discovered in Garden Park, Colorado, in rocks belonging to the Morrison Formation. The type species is Ceratosaurus nasicornis.
The Morrison Formation is a distinctive sequence of Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone, and limestone and is light gray, greenish gray, or red. Most of the fossils occur in the green siltstone beds and lower sandstones, relics of the rivers and floodplains of the Jurassic period.
Torvosaurus is a genus of large megalosaurine theropod dinosaur that lived approximately 165 to 148 million years ago during the Callovian to Tithonian ages of the late Middle and Late Jurassic period in what is now Colorado, Portugal, Germany, and possibly England, Spain, Tanzania, and Uruguay. It contains two currently recognized species, Torvosaurus tanneri and Torvosaurus gurneyi, plus a third unnamed species from Germany.
Barosaurus was a giant, long-tailed, long-necked, plant-eating sauropod dinosaur closely related to the more familiar Diplodocus. Remains have been found in the Morrison Formation from the Upper Jurassic Period of Utah and South Dakota. It is present in stratigraphic zones 2–5.
Dryosaurus is a genus of an ornithopod dinosaur that lived in the Late Jurassic period. It was an iguanodont. Fossils have been found in the western United States and were first discovered in the late 19th century. Valdosaurus canaliculatus and Dysalotosaurus lettowvorbecki were both formerly considered to represent species of Dryosaurus.
Antrodemus is a dubious genus of theropod dinosaur from the Upper Jurassic, probably the Morrison Formation, of Middle Park, Colorado. It contains one species, Antrodemus valens, first described and named as a species of Poekilopleuron by Joseph Leidy in 1870.
Saurophaganax is a genus of large allosaurid dinosaur from the Morrison Formation of Late Jurassic Oklahoma, United States. Some paleontologists consider it to be a junior synonym and species of Allosaurus. Saurophaganax represents a very large Morrison allosaurid characterized by horizontal laminae at the bases of the dorsal neural spines above the transverse processes, and "meat-chopper" chevrons. It was the largest terrestrial carnivore of North America during the Late Jurassic, reaching 10.5 metres (34 ft) in length and 2.7–3.8 metric tons in body mass.
Stokesosaurus is a genus of small, carnivorous early tyrannosauroid theropod dinosaurs from the late Jurassic period of Utah, United States.
Marshosaurus is a genus of medium-sized carnivorous theropod dinosaur, belonging to the Megalosauroidea, from the Late Jurassic Morrison Formation of Utah and possibly Colorado.
Lourinhanosaurus was a genus of carnivorous theropod dinosaur that lived during the Late Jurassic Period (Kimmeridgian/Tithonian) in Portugal. It is one of many large predators discovered at the Lourinhã Formation and probably competed with coeval Torvosaurus gurneyi, Allosaurus europaeus, and Ceratosaurus.
Palaeopteryx is an extinct genus of dubious paravian theropod dinosaur from the Morrison Formation of Colorado. The type species is P. thomsoni.
James Alvin Jensen was an American paleontologist. His extensive collecting program at Brigham Young University in the Utah–Colorado region which spanned 23 years was comparable in terms of the number of specimens collected to that of Barnum Brown during the early 20th century. He was given the name "Dinosaur Jim" during the media coverage of his activities. Perhaps his most significant contribution to paleontology was to replace the 19th-century web of external metal struts, straps and posts that had been used to mount dinosaurs with a system of supports which were placed inside of bones, which produced free-standing skeletons with few or no obvious supports.
Hesperornithoides is a genus of troodontid theropod dinosaur that lived in North America during the Late Jurassic period.
Camarasaurus lentus is an extinct species of sauropod dinosaur that lived during the Jurassic period in what is now the western United States. It is one of the four valid species of the well-known genus Camarasaurus. C. lentus fossils have been found in Wyoming, Colorado, and Utah. It is the species of Camarasaurus found in Dinosaur National Monument and the middle layers of the Morrison Formation. Camarasaurus lentus is among the best-known sauropod species, with many specimens known. A juvenile specimen of C. lentus, CM 11338, is the most complete sauropod fossil ever discovered.
Brachiosaurus is a genus of sauropod dinosaur that lived in North America during the Late Jurassic, about 154 to 150 million years ago. It was first described by American paleontologist Elmer S. Riggs in 1903 from fossils found in the Colorado River valley in western Colorado, United States. Riggs named the dinosaur Brachiosaurus altithorax; the generic name is Greek for "arm lizard", in reference to its proportionately long arms, and the specific name means "deep chest". Brachiosaurus is estimated to have been between 18 and 22 meters long; body mass estimates of the subadult holotype specimen range from 28.3 to 46.9 metric tons. It had a disproportionately long neck, small skull, and large overall size, all of which are typical for sauropods. Atypically, Brachiosaurus had longer forelimbs than hindlimbs, which resulted in a steeply inclined trunk, and a proportionally shorter tail.
Uteodon is a genus of herbivorous iguanodontian dinosaur. It is a basal iguanodontian which lived during the late Jurassic period in what is now Uintah County, Utah. It is known from the middle of the Brushy Basin Member, Morrison Formation. The genus was named by Andrew T. McDonald in 2011 and the type species is U. aphanoecetes.