Salt Lake City—The collaboration of Utah paleontologists with Spanish and English researchers has led to identification of the correct familial relationships of the new Utah dinosaur.
Although the Doellings Bowl Bonebed was first identified by Utah State Paleontologist James Kirkland in 1991, the age and great extent of skeletal remains at the site were not recognized until 2006. Following a flash flood in 2010, some large bones were observed by former UGS geologist Gary Hunt of Enterprise, Utah at the base of a dry wash adjoining the original dig site. Excavation of these bones revealed the skeleton of a mired sauropod or long-necked dinosaur with both a fore limb and hind limb extended down into the marsh deposit below the level of the rest of the skeleton. The excavation team, led by Dr. James Kirkland of the Utah Geological Survey, discovered and prepared two sauropod specimens, one of them very complete, including the skull.
The Doellings Bowl Bone Bed is in the lower Yellow Cat Member of the Cedar Mountain Formation near the very base of Utah’s thick and very fossiliferous Cretaceous sequence. The Yellow Cat Member is divided into an upper and lower sequence as it preserves two non-overlapping dinosaur faunas separated by a well-developed fossil soil horizon representing significant time on the order of one to a few million years. It has been shown recently that the Yellow Cat Member in Grand County, Utah preserves the TWO oldest dinosaur faunas because Early Cretaceous salt movement induced subsidence, creating a protected depression in the northern Paradox “salt” Basin while the rest of western North America was undergoing erosion. https://geology.utah.gov/map-pub/survey-notes/preserve-cret-dino-salt-deposits/
The presence of silicified peat, fern roots, tiny fish bones, rare turtles and rare crocodilian fossils suggests the Doellings Bowl Bonebed represents a marsh deposit. Mierasaurus coexisted in the same ecosystem as the ornithopod Iguanacolossus, an armored polacanthid ankylosaur (not yet described), small “raptors” (carnivorous dinosaurs), such as Yurgovuchia, large allosaurid theropods, and a large, primitive therizinosaur. The environmental interpretation for the site where Mierasaurus was discovered was a marsh area with vegetation of ferns that was climatically wetter than that indicated for both the underlying Upper Jurassic Morrison Formation and overlying upper Yellow Cat Member.
The specific age of these rocks is controversial but new data is being published. Our best current estimates are approximately 130-135 Ma (millions of years ago); see: https://www.utahgeology.org/openjournal/index.php/GIW/article/view/9
The collaboration of Utah paleontologists with Spanish and English researchers led to identification of the correct familial relationships of the new Utah dinosaur. While it is obviously a new dinosaur species, without the collaboration Kirkland’s team would almost certainly have compared the new dinosaur with North America’s well-known Upper Jurassic sauropod Camarasaurus. As it turned out, Dr. Rafael Royo-Torres first recognized the more primitive turiasaurs as a distinct group of European Upper Jurassic sauropods.
During 2016 and 2017 the description and comparison of the new remains was conducted by an international multidisciplinary team composed of Dr.s Rafael Royo-Torres, Alberto Cobos and Luis Alcalá from the Fundación Conjunto Paleontológico de Teruel-Dinópolis (Teruel, España), Paul Upchurch from the University College London (London, United Kingdom), James Kirkland and Donald D. DeBlieux from the Utah Geological Survey (Utah, USA), and John Foster from the Museum of Moab (Utah, USA).
This new paper, published in the journal “Scientific Reports,” contains several milestones:
- Description of a new genus and species of sauropod dinosaur (quadruped, with long neck and tail and small skull);
- identification of a group of Upper Jurassic European dinosaurs, the Turiasauria, not identified in North America prior to this study;
- Given the evolutionary relationships of the Turiasauria, Mierasaurus is the most primitive sauropod identified in North America, though actually younger than many Jurassic N.A. sauropods
- Recognition that a second North American sauropod from the upper Yellow Cat fauna, Moabosaurus, also belonged to the group of Turiasauria;
- Moabosaurus is more specialized than the older Mierasarus in having divided ribs along its neck; and
- Recognition that the Cretaceous turiasaurs in North America are the geologically youngest known so far.
Recovered fossils (from the skull, teeth, neck, back and tail, bones of the shoulder and hips, and bones of the front and back limbs, including the hands and feet) allow us to state that this new specimen, Mierasaurus, represents the most complete individual sauropod dinosaur from the Cretaceous of North America. In addition, Mierasaurus (as well as Moabosaurus) are sauropods with more primitive characteristics, when compared to other sauropods from North America. The length of Mierasaurus, estimated between 32-39 feet (10 and 12 meters), is much smaller than that of its European relatives, which in Turiasaurus could surpass 82 feet in length (25 meters).
How did the turiasaurs arrive to North America from Europe? The study indicates that none of the more than 430 examples of sauropods documented in North American sites from the Upper Jurassic are turiasaurs. The Turiasauria were well-represented in the Jurassic only in Europe. The discovery of the turiasaurs Mierasaurus and Moabosaurus in younger deposits, in the Lower Cretaceous Yellow Cat Member of the Cedar Mountain Formation in Utah, allows scientist to infer that representatives of this group of primitive sauropods migrated into North America via an intercontinental bridge, after the Upper Jurassic (between 145 and 130 million years ago) from Europe, during the final opening of the North Atlantic during a time of lower sea levels.
The name of the genus of the new dinosaur, Mierasaurus, is dedicated to the Spanish cartographer and chief scientist D. Bernardo de Miera y Pacheco (1713-1785), born in Santibáñez de Villacarriedo (Cantabria, Spain). Miera was the scientific leader of the 1776 Domínguez-Escalante Expedition. The purpose of the expedition was to establish a stable communication and trade route between Santa Fe, New Mexico, and Monterrey, California. For six months, they traveled 2,000 miles, establishing peaceful contact with numerous groups of native Americans (Hopis, Lagunas, Yutas and Apaches, among others). Bernardo de Miera y Pacheco made the first map of this territory, largely unknown to Europeans at this time. This map stands out for its accuracy and artistic style, and for the numerous geographic, geological and ethnographic notes that it contains. This expedition was also the first known arrival of Europeans into what is now the state of Utah, where Mierasaurus was discovered. The name of the species, bobyoungi, is dedicated to the American geologist Robert Young, who conducted the first comprehensive work on the Early Cretaceous of the Colorado Plateau, where Mierasaurus was discovered.