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The AAPG/Datapages Combined Publications Database
Grand Junction Geological Society
Abstract
The Dry Mesa Dinosaur Quarry, Mesa County, Colorado
Abstract
Dry Mesa Dinosaur Quarry in southwestern Colorado was established in 1972 after discovery of a large theropod phalanx found the previous year. This quarry has produced several thousand fossil bones, mostly dinosaur, in the 12 field seasons in which collecting has taken place. Although study of the fauna is still in initial stages, it has been shown that the diversity of dinosaurs here far exceeds that for any other single quarry in the Morrison Formation. Preliminary research reveals the probability of 22 genera and species. Included are 18 genera of saurischians and 4 of ornithischians. To date four new genera and species have been reported from this fauna: Torvosaurus tanneri, Supersaurus vivianae, Ultrasaurus mcintoshi and Dystylosaurus edwini. A new genus and species of pterosaur, Mesadactylus ornithosphyos, has also come from the quarry. This flying reptile along with bones of fish, amphibian, turtle, lizard, crocodile, avian-like reptile and mammal constitute a small but interesting non-dinosaurian assemblage.
Faunal aspect and preliminary fission track dating suggest a latest Jurassic/earliest Cretaceous age for the Dry Mesa Dinosaur Quarry. Paleobotanical evidence is not available to demonstrate what the vegetation and climate were like in this area at that time. However, a significant number of plants must have existed to sustain the large sauropods present. Geological evidence indicates the presence of at least a moderate sized stream in the vicinity of the site. Earlier authors differ in opinion whether the Morrison Formation indicates mostly humid or mostly arid conditions. If climatic conditions were arid in southwestern Colorado during the time bones were being deposited at Dry Mesa, then a substantial riparian flora must have existed there. We interpret the deposits at the site to represent a fairly large stream which flowed over a well developed floodplain.
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