The Doelling’s Bowl Bonebed is particularly important as it sits below a marker calcrete bed that had formally been used to mark the base of the Cretaceous and is thus older than previously studied Lower Cretaceous Dinosaur Sites in the area. Several additional new dinosaur species (iguanodonts, sauropods, carnosaurs, polacanthine ankylosaurs and hypsilophodonts) are being excavated by the UGS at this site and are under study.
These new dinosaurs are from the Yellow Cat Member of the Cedar Mountain at the base of the Cretaceous in eastern Utah. These rocks have yielded an exciting new suite of dinosaurs in the last few years, whose rouges gallery of newly named theropods (meat-eating dinosaur) species, in addition to Yurgovuchia, includes coelurosaur Nedcolbertia justinhofmanni, and the giant dromaeosaurid Utahraptor ostrommaysorum from above the calcrete and the therizinosauroid Falcarius utahensis, the troodontid Geminiraptor suarezarum from below a distinctive “caprock” about 40 kilometers to the west. Unfortunately. we still have no means of correlating the “caprock” with the marker calcrete and still have no dinosaur species in common from the basal Yellow Cat Mbr. in the two areas.
The new tail described in this paper is from above the marker calcrete bed and recovered from Andrew’s Site, a locality a few miles to the west that yielded the iguanodont Hippodraco that was formally named in 2010. Andrew’s Site was discovered by Andrew Milner paleontologist at the St. George Dinosaur Discovery Site at Johnson Farm. This tail is distinctive in the long extensions of bone off of each vertebrae stiffing the tail as a balancing organ. Although not providing enough information to permit the species to be properly defined, the fossil proves that there were more advanced dromaeosaurs like Velociraptor and Deinonychus living in the same habitats as the giant but more primitive Utahraptor.
The paper describing these new dinosaurs “New dromaeosaurids (Dinosauria: Theropoda) from the Lower Cretaceous of Utah and the evolution of the dromaeosaurid tail” was published yesterday in PLos One (Public Library of Science) as part of a collaboration between UGS paleontologists and Phil Senter, from Fayetteville University in North Carolina. I have two admit I’m troubled that Deinonychus, with its more derived tail, forms a clade with Utahraptor and Yurgovuchia among the dromaeosaurines in Phil Senter’s phylogenetic analysis, but such things change with recognition of new character states.