Cartilage correction makes dinos taller, according to articles in ScienceDaily and ScienceShots 30 Sept 2010 and ABC News in Science, 1 Oct 2010. The height of dinosaurs is estimated by placing the bones together, but according to anatomists Casey Holliday of University of Missouri and Lawrence Witmer of Ohio University, most reconstructions do not take account of the soft tissues between the bones. The ends of bones that form joints with other bones have thick layers of cartilage over their surfaces to facilitate smooth movement. Cartilage does not fossilise so it is not possible to measure exactly how much the ends of bones were separated in living dinosaurs. Therefore, Holliday and Witmer studied bones of ostriches and alligators to get an idea of the proportion of cartilage to bone in the length of the limb bones. Holliday explained: “The ends of many dinosaurs’ long bones, which include leg bones such as the femur or tibia, are rounded and rough and lack major articulating (joint forming) structures like condyles, which are bony projections. This indicated that very thick cartilages formed these structures, and therefore the joints themselves, and would have added significant height to certain dinosaurs. This study offers new data into how and why reptiles, and mammals, such as humans, build their joints with such different amounts of bone and cartilage.” The results suggest that some of the large dinosaurs such a Brachiosaurus could have been 30cm (one foot) taller than previous estimates. Witmer commented: “This study is significant because it shows that bones can’t always speak for themselves. To understand how dinosaurs moved, we need to analyze the bones as they were inside their bodies, including their cartilage. The dinosaur bones mounted in museums don’t accurately reflect what the animals actually had in their bodies in life because the cartilage caps were lost along with the other soft tissues. Knowing how much cartilage was lost allows us to better restore the structure of a living dinosaur bone, which then allows us to better understand how dinosaurs moved and lived.”
Editorial Comment: This is a good reminder that there is far more to a living creature than its bones, and many of the lifelike reconstructions displayed in museum and in wildlife documentaries are mostly imagination, rather than facts. In fact, for many dinosaurs, not even whole skeletons have been found – just a few bones. There is nothing wrong with making reconstructions, but it is important to clearly state what are the facts and what are the assumptions the reconstruction is made on. After all, even T rex is up to his fourth reconstruction! (Ref. osteology, fossils, palaeontology)
Evidence News 27 Oct 2010