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).