The Cedar Mountain Formation of the western United States, which is dated to the early Cretaceous Period, has produced fossils of numerous dinosaur species. Several of these are still not officially classified, and this post concerns one of them.
In 2004, Dr. Andrew R. C. Milner, a paleontologist and curator of the St. George Dinosaur Discovery Site at Johnson Farm, Utah, was prospecting for fossils in an area northeast of Arches National Park. At a place which was dubbed “Andrew’s Site”, which contained rocks dating to the early part of the Cedar Mountain Formation, he and his colleagues discovered the fossilized remains of several dinosaurs. Among the fossils which were found was a partial right scapula, or shoulder blade (collections ID code: UMNH VP 20644). This was quite unlike many of the other bones which were found there which belonged to much larger plant-eating dinosaurs. The shoulder blade was provisionally identified as belonging to a small Hypsilophodon-like ornithopod dinosaur. Hypsilophodon was a small 6 foot long plant-eating dinosaur whose remains have been found in England within rocks dating to the early Cretaceous Period. Based upon the scapula’s size in comparison with the size of the shoulder blade of Hypsilophodon, the creature that this shoulder blade once belonged to was perhaps the same size or slightly larger compared to its European relative. My guess is that this animal reached somewhere around 6 to 8 feet long.
Below is a reconstruction of what I think this enigmatic plant-eater would have looked like. I didn’t want to make it an exact copy of Hypsilophodon, but instead wanted it to look Hypsilophodon-ish. Much of this drawing is conjecture, and it should not be taken to be a 100% accurate representation of this animal. The drawing was made with No.2 and No.3 pencil on printer paper, and was afterwards colored with Crayola and Prismacolor colored pencils. As far as the color goes, I wanted to do something bit different. Many animals are colored in what’s called “counter-shading”, with darkly-colored backs and lightly-colored bellies. However, what about the opposite? “Reverse counter-shading” is rare in nature, but I wanted to see how it might look on this creature, and I’m generally pleased with how it turned out.
Un-named hypsilophodont dinosaur from the upper part of the Yellow Cat Member of the Cedar Mountain Formation. © Jason R. Abdale (February 18, 2022).
McDonald, Andrew T.; Kirkland, James I.; DeBlieux, Donald D.; Madsen, Scott K.; Cavin, Jennifer; Milner, Andrew R. C.; Panzarin, Lukas (2010). “New basal iguanodonts from the Cedar Mountain Formation of Utah and the evolution of thumb-spiked dinosaurs”. PloS One, v. 5, no. 11, e14075, doi:10.1371/journal.pone.0014075;