r By The Utah Geological Survey
The collaboration of Utah paleontologists with Spanish and English researchers has led to the identification of the correct familial relationships of a 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 forelimb and hindlimb 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.
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, is much smaller than that of its European relatives, which in Turiasaurus could surpass 82 feet in length.
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 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).
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.