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This is Camptosaurus dispar, a 20 foot long plant-eating dinosaur from the Morrison Formation of western North America during the late Jurassic Period. In most paleo-art, it seems that the only purpose in life for this unfortunate animal is to be Allosaurus‘ lunch! It’s not hard to see why – a large meaty animal with little or no defenses would make a fine meal for a hungry carnivore.
The first fossils of this animal were discovered on September 4, 1879 by William H. Reed in Wyoming during the famous “Bone Wars”. Later that year, Prof. Othniel Charles Marsh named the animal Camptonotus, meaning “bent back” due to its curved spine. However, he was forced to change it because another animal had already been given that name. In 1885, the dinosaur was re-named Camptosaurus, “the bent lizard”.
Below is an illustration of a hypothetical complete skeleton of Camptosaurus which was published in The American Journal of Science in 1894. Based upon what we now know of the skeleton, there are a few mistakes seen in this drawing: the skull is the wrong shape, the arms are far too small, and the torso is too stretched-out.
Marsh, Othniel Charles. “Restoration of Camptosaurus“. The American Journal of Science, volume XLVII (1894). Plate VI. Click here to read the whole article: https://archive.org/details/b22320714/mode/2up.
Camptosaurus was a primitive member of a clade of ornithopod dinosaurs called “Ankylopollexia”, which includes the iguanodonts and the hadrosaurs. Unlike other herbivorous dinosaurs, Camptosaurus and its descendants had chewing teeth, which helped them to process their food better which in turn helped their digestive systems to extract more nutrients. One of the most well-known features of the iguanodonts was the presence of a thumb spike. On Iguanodon, the thumb spike was rather large. Being an ancestor of this group, Camptosaurus also had a thumb spike, but it was comparatively tiny, almost the same size as its other finger claws, and would have been pretty much useless as a weapon, but hey we all have to start off somewhere. Camptosaurus was related to the 10 foot long ornithopod Dryosaurus, which lived in the same habitat, although Camptosaurus was more advanced.
Paleontologists are still arguing whether Camptosaurus was primarily bipedal or quadrupedal. Personally, while I believe that Camptosaurus was capable of going down on all fours (making it a “facultative quadruped”), I think that it was bipedal most of the time.
It has been proposed that Camptosaurus and the large armored herbivore Stegosaurus may have established a symbiotic relationship out on the plains of the Morrison Formation. This hypothesis is largely due to the observation that fossils of these two animals are often found in association with each other. According to the hypothesis, Camptosaurus possessed larger eyes and a somewhat larger brain, and would have served as early warning lookouts for predators like Allosaurus, Ceratosaurus, and Torvosaurus. When danger threatened, Stegosaurus would provide protection from attack. It’s an interesting idea, but I’m not sure how much water this holds. Just because fossils of two animals are often found in close proximity to one another, that does not necessarily denote a relationship. We have fossils of numerous species gathered together in one place, but this does not automatically denote mutual cooperation.
Note: The three original drawings that I posted here in April 2020 were removed because they were anatomically inaccurate, and in general I wasn’t really happy with the way that they looked. The drawings that you see below were added in April 2021.
Below are two drawings which I made of this animal. The first drawing was made with No. 2 pencil, and the colorized drawing was done with assorted colored pencils and quite a bit of touching-up on the computer (the scanner has a tendency to fade the colors).
Camptosaurus dispar. © Jason R. Abdale (April 15, 2021).
Camptosaurus dispar was a type of ornithopod ornithischian dinosaur which lived in western North America during the late Jurassic Period. It measured 20 feet long and possibly weighed a ton. Camptosaurus was the largest ornithopod found within the Morrison Formation. Other ornithopods include the 10-foot long Dryosaurus and the 5-foot long Othnielia.
Camptosaurus was discovered on September 4, 1879 by William Reed in Wyoming during the famous “Bone Wars”. Othniel Charles Marsh originally named the animal Camptonotus, but was forced to change it because another animal had already been given this name. In 1885, the dinosaur was re-named Camptosaurus.
For a long time, we thought we knew what Camptosaurus looked like, or at least what its head looked like. Publications as recent as the 1990s depicted Camptosaurus with a boxy rectangular-shaped skull. This is due to paleontologist Charles W. Gilmore. In 1909, Gilmore wrote a description of the genus Camptosaurus and its assorted species. A skull (YPM 1887), referred to in 1886 by Marsh as belonging to Camptosaurus amplus, was re-designated by Gilmore as belonging to Camptosaurus dispar. In 1980, Peter Galton and H. P. Powell stated that C. nanus, C. medius, and C. browni were not separate species, but were instead growth stages of C. dispar, making C. dispar the only valid species. They also used the skull catalogued as YPM 1887 as the skull of Camptosaurus dispar. For many years, this was taken as fact, and this skull was used in many illustrations of Camptosaurus. However in 2006, Kenneth Carpenter and K. Brill found that this skull actually belonged to a different dinosaur. The skull, and the animal associated with it was named Theiophytalia kerri.
Below is the traditional-but-incorrect depiction of what Camptosaurus‘ skull looked like. Image from The Dinosaur Data Book, by David Lambert. New York: Avon Books, 1990. Page 180. The original image has been modified so that the labels have been removed.
So what did Camptosaurus really look like? The skull was more triangular in shape, similar to that of Dryosaurus. However, it was not a close relative. According to current phylogenics, Camptosaurus was more advanced than Dryosaurus, but more primitive than Iguanodon and hadrosaurs.
The illustration which you see below is the current look of Camptosaurus. However, I should state that the old rectangular image is so prevalent that it will take quite some time before old-school paleo-buffs like me learn to disregard it. This drawing was made with regular No. 2 pencil (my favorite medium) on basic computer paper.
Keep your pencils sharp, everyone.