Hagit asked: I would like to know how many whole skulls of dinosaurs have been found to date? Has any dinosaur been found in its entirety; body and skull included? Has a body been found in close proximity to its skull? If not found in close proximity, how is the body associated with the head?
Let’s start by stating the work of a paleontologist is not an easy task. The paleontologist has to find fossils buried inside a rocky layer in the ground, with only fossilized hard body parts (mostly bones). Thus, it is very rare to come across a skeleton of a whole dinosaur, though it does occur from time to time.
The skull is considered to be an extremely rare fossil, since it is composed of many parts, which fall apart and separate a short time after the animal dies. The average skull is composed of over twenty different parts, not including the teeth, and it has no joints to hold them attached to the rest of the skeleton after the meat has rotted away
In contrast, tooth fossils are relatively widespread since teeth are covered with an enamel layer that strengthens them, making them more resistant to the damages of time. Actually, the first dinosaur fossil to ever be discovered and defined was a fossilized tooth. This fossil was found by the wife of Gideon Algernon Mantell, an English doctor and amateur geologist who looked at the interesting stone and almost immediately deduced it was a tooth of a large reptile that lived in the Mesozoic era. Since the tooth resembled that of an iguana, the first dinosaur to be discovered was given the name “Iguanodon”.
Archaeopteryx Lithographica fossil, an ancient flying reptile | Photograph by: H. Raab, Wikipedia
So, how is it possible to know what bone belongs to which dinosaur? It really isn’t that simple. Researchers rely on the location in which the fossil was found, the shape of the bones and teeth, as well as a comparison to more complete skeletons that are already familiar to the researchers and were previously discovered in the area. The first attempts to reconstruct dinosaur skeletons seems strange to us today, since researchers did not have anything to rely on back then. The first model of the Iguanodon resembles a dog, with its famous toenail stuck to its nose. The Stegosaurus was first assembled with its back plates covering it like roof shingles.
Regarding the number of skeletons found to date – this is a great question since the number of complete components is relatively small (the average dinosaur has about a hundred different bones). Currently it is estimated that around 2,100 “good skeletons” have been found, and the number of known species is several hundred (300-500). Therefore, even without an entire skeleton, but with other skeletons from the same species, we have a good chance of completing the full picture. In addition, researchers often rely on the bone structure of contemporary reptiles and birds, which are the descendants of the dinosaurs and therefore their distant relatives.
Another type of dinosaur fossil is when the body of the animal has not decomposed, but rather was washed away into a body of water and was covered in mud. These fossils are called “mummies”, and traces of fossilized soft tissues such as muscle and even skin can be detected in them. To date, only a few dinosaur mummies have been found. The method of working with this type of fossil is different than that of classical paleontology. Here the researcher replaces their chisel and hammer with MRI machines and computerized imaging software. In addition, the bones of the animal are not dug out of the ground, but the whole chunk of rock is taken out. The chunk is casted so it will not deteriorate, and then it is entered into a CT machine, which is also used for airplanes. Using this it is possible to image the internal tissues of the fossilized animal.
More about mummies – a video from the Discovery Channel's Secrets of the Dinosaur Mummy: Analysis of the mummy of the Hadrosaur Leonardo, with paleontologist Bob Becker:
Davidson Institute for Science Education
Weizmann Institute of Science
Article translated from Hebrew by Elee Shimshoni, PhD student at the Weizmann Institute of Science.