Cedrorestes, which means “Cedar Mountain dweller”, was an ornithopod dinosaur which lived in Utah during the early Cretaceous Period. The fossils of this animal were discovered in eastern Utah in 2001. These were fragmentary remains consisting of pieces of ribs, parts of the hip, a right femur, a single metatarsal from the right foot, and sections of ossified tendons (presumably belonging to the tail). The fossils were found in mudstone layers which were positioned at the top of the Yellow Cat Member of the Cedar Mountain Formation, circa 132 MYA.
In the 2007 article which named it, the authors classified Cedrorestes as a basal hadrosauriform (Gilpin et al 2007, page 81, 86-88; Prieto-Márquez 2010, page 1), but others aren’t so sure, claiming that it’s an iguanodontian of some sort (Ramirez-Velasco et al 2012, page 389). This is partly due to the incompleteness of the fossil remains which makes it difficult to identify, and partly because the few bones which have been found show features belonging to both ornithopod groups. Because only partial remains have been discovered, it’s uncertain how large Cedrorestes would have been when fully grown. Multiple online sources typically give lengths of 5-6 meters (16.4-19.7 feet long).
It’s possible that Cedrorestes is the same as another plant-eating dinosaur from the Cedar Mountain Formation called Planicoxa. Fossils of Cedrorestes were found within the Yellow Cat Member, while those belonging to Planicoxa were found in the overlying Poison Strip Member, so it’s slightly younger. Planicoxa was named in 2001 (DiCroce and Carpenter 2001, pages 183-196), and Cedrorestes was named in 2007 (Gilpin et al 2007, pages 79-89). If it’s true that these two genera are actually one-and-the-same, then the name Planicoxa takes priority because it was named first.
As far as I’m aware, the prospect that Planicoxa and Cedrorestes are synonymous was first proposed by Jim Kirkland and Scott Madsen in 2007 shortly after Cedrorestes was named. In their paper, they make the following statement: “In 2006, Gilpen and others (2006) described the iguanodont Cedroestes (sic) crichtoni from the Poison Strip Sandstone solely on the basis of a prominent ‘antitrochanter’ dorsal to the ischial peduncle. This same feature is present, although not so well developed, in the juvenile holotype of Planicoxa, and examination of the illia in both specimens indicates than any differences between the specimens can be explained by ontogeny and distortion. Thus, Cedroestes (sic) is a junior synonym of Planicoxa” (Kirkland and Madsen 2007, page 12).
In 2010, McDonald et al re-examined these specimens, and they concluded that Planicoxa and Cedrorestes were two separate genera: “A recent reassessment of P. venenica revealed that the holotype ilium (DMNH 42504) differs from that of Cedrorestes in having a convex dorsal margin and both taxa are reservedly treated as viable” (McDonald et al 2010: e14075).
Currently, most sources treat these two creatures as two entirely separate genera. Personally, I don’t think that having a slight variation in the ilium is enough to warrant naming a new genus. It’s possible that Cedrorestes crichtoni ought to be reclassified as Planicoxa crichtoni, differentiated from P. venenica by the shape of the ilium. However, until a comprehensive analysis is made specifically comparing the anatomy of these two genera point-by-point, their separation into two taxa will likely have to remain in place.
Below is a drawing that I made of Cedrorestes. No skull elements were found with the specimen, so the animal’s appearance is based upon other primitive hadrosauriforms like Mantellisaurus, Probactrosaurus, Bolong, Choyrodon, and Eolambia. The drawing was made in 1/12 scale, measuring 20 inches long, and was made using an ordinary black ballpoint pen on printer paper. It was afterwards colored in Prismacolor colored pencils.
Cedrorestes crichtoni. © Jason R. Abdale (November 24, 2022).
Keep your pencils sharp, people. And don’t let your pens and markers dry out, either.
Bibliography
DiCroce, Tony; Carpenter, Kenneth (2001). “New Ornithopod from the Cedar Mountain Formation (Lower Cretaceous) of Eastern Utah”. In Tanke, Darren; Carpenter, Kenneth, eds., Mesozoic Vertebrate Life. Bloomington: Indiana University Press, 2001. Pages 183-196.
https://www.researchgate.net/publication/314984434_New_Ornithopod_from_the_Cedar_Mountain_Formation_Lower_Cre-_taceous_of_Eastern_Utah.
Gilpin, David; DiCroce, Tony; Carpenter, Kenneth (2007). “A Possible New Basal Hadrosaur from the Lower Cretaceous Cedar Mountain Formation of Eastern Utah”. In Carpenter, Kenneth, ed., Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs. Bloomington: Indiana University Press, 2007. Pages 79-89.
https://www.researchgate.net/publication/314886422_A_Possible_New_Basal_Hadrosaur_from_the_Lower_Cretaceous_Cedar_Mountain_Formation_of_Eastern_Utah.
Kirkland, James I.; Madsen, Scott K. (2007). “The Lower Cretaceous Cedar Mountain Formation, eastern Utah: the view up an always interesting learning curve”. Fieldtrip Guidebook, Geological Society of America, Rocky Mountain Section. 2007 Geological Society of America Rocky Mountain Section Annual Meeting, St. George, Utah (May 4-6, 2007). Pages 1-108.
https://www.researchgate.net/publication/40662964_The_Lower_Cretaceous_Cedar_Mountain_Formation_eastern_Utah_the_view_up_an_always_interesting_learning_curve_papers_from_a_symposium_of_the_Geological_Society_of_America_at_the_annual_meeting_in_St_Geo.
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, volume 5, issue 11 (November 22, 2010): e14075.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0014075.
Prieto-Márquez, Albert (2010). “Glishades ericksoni, a new hadrosauroid (Dinosauria: Ornithopoda) from the Late Cretaceous of North America”. Zootaxa, volume 2452 (May 12, 2010). Pages 1-17.
Ramirez-Velasco, Angel Alejandro; Benammi, Mouloud; Prieto-Marquez, Albert; Alvarado Ortega, Jesus; Hernández-Rivera, Rene (2012). “Huehuecanauhtlus tiquichensis, a new hadrosauroid dinosaur (Ornithischia: Ornithopoda) from the Santonian (Late Cretaceous) of Michoacán, Mexico”. Canadian Journal of Earth Sciences, volume 49, issue 2 (February 2012). Pages 379-395.
https://www.researchgate.net/publication/233426576_Huehuecanauhtlus_tiquichensis_a_new_hadrosauroid_dinosaur_Ornithischia_Ornithopoda_from_the_Santonian_Late_Cretaceous_of_Michoacan_Mexico.
Categories: Paleontology, Uncategorized
DINOSAURS AND BARBARIANS 
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