October 1, 2010

Researchers Find Dinosaurs Taller Than Previously Thought

Dinosaurs may have been taller than originally thought, according to new research which claims that thick layers of cartilage in their joints could have made some of the prehistoric lizards more than 10% taller than previously believed.

The study, which was conducted by researchers at the University of Missouri (MU) and Ohio University (OU), also asserts that the additional cartilage might have had an impact on their speed and their posture as well. The findings have been published in the journal PLoS-ONE.

"Our study of the limbs of modern-day relatives of dinosaurs shows that dinosaurs were significantly taller than original estimates," Casey Holliday, lead author of the study and an anatomy professor at the MU School of Medicine, said in a statement Thursday.

"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 structures like condyles, which are bony projections," he added. "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."

Holliday worked with OU anatomy professor Lawrence Witmer on the study, which analyzed both the fossilized limbs of different dinosaur species and modern-day creatures related to the now-extinct reptiles, including ostriches and alligators.

They found that the limbs of alligators and ostriches included between 6% and 10% cartilage, and by using what they called a "cartilage correction factor," they discovered that some species (including ornthischians and saurpods) could have been more than 10% taller than original believed. For example, the Brachiosaurus may have been 43 feet tall--a full foot taller than previously estimated, according to an MU press release dated September 30.

"This study is significant because it shows that bones can't always speak for themselves," Witmer said. "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."


Image Caption: These two sets of bones demonstrate how much cartilage could have been on dinosaur bones. The top "bone" is a cast of the bone with cartilage, compared to the actual bone with no cartilage. This allows researchers to study the difference and determine how much length might be added with the addition of cartilage. Credit: University of Missouri


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