New Hi-tech Study Finds T. rex was Bigger and Grew Faster than Previously Thought

Posted by pt91 at Oct 27, 2011 03:23 PM |
Jane, the T. rex replica at University of Leicester, contributes to new findings
New Hi-tech Study Finds T. rex was Bigger and Grew Faster than Previously Thought

'Jane', the University's resident T. rex (replica).

Issued by the University of Leicester Press Office on 27 October 2011

Jpeg image of Jane, the T.rex replica at University of Leicester, available from pressoffice@le.ac.uk

In a new study just published in the journal PLoS One, a team of scientists led by Professor John R. Hutchinson of The Royal Veterinary College, London, and Peter Makovicky, PhD, curator of dinosaurs at The Field Museum of Natural History in Chicago applied cutting edge technology and computer modeling to “weigh” five Tyrannosaurus rex specimens, including The Field Museum’s iconic SUE skeleton. Their results reveal that T. rex grew more quickly and reached significantly greater masses than previously estimated.

In a departure from earlier methods, the new study uses mounted skeletons to generate body mass estimates. Makovicky notes, “Previous methods for calculating mass relied on scale models, which can magnify even minor errors, or on extrapolations from living animals with very different body plans from dinosaurs. We overcame such problems by using the actual skeletons as a starting point for our study.”

A cast of a 21-foot long T. rex (a rare, sub-adult individual), commissioned from the makers of specimens of T. rex that featured in the film ‘Jurassic Park’ and  which is  on permanent display at the University of Leicester Department of Geology, was instrumental in the research.

The Leicester exhibit, sponsored by Aggregate Industries, was the first of its kind to ever be showcased in this country and is the cast of  the most complete sub-adult skeleton of a T. rex ever found.

The team used 3D laser scans of mounted skeletons as a template for generating fleshed-out digital models whose masses could then be computed. The laser scans are accurate to less than half an inch for skeletons that are up to 40 feet long. Digital body cross-sections were reconstructed along the length of each skeleton using the relationships of the soft tissues to skeletons in birds and crocodiles as a guide. A digital skin was then overlaid to generate a body volume, whose mass was calculated after empty spaces such as lungs and the mouth cavity were modeled and subtracted.

In order to appreciate the uncertainty involved in estimating how much flesh would wrap the skeleton of an extinct animal, body sections (e.g. head, neck, torso, legs, tail) were modelled individually at three levels of ”fleshiness.” The three versions of each body segment were combined in different ways to generate a range of whole body models with varying masses.

“These models range from the severely undernourished through the overly obese, but they are purposely chosen extremes that bound biologically realistic values” says study co-author Dr. Vivian Allen of the Royal Veterinary College. ”The real advantage to our method is that the models can be adjusted to accommodate the variation that is inherent in nature, so we don’t have to pick an arbitrary result, but rather deal with more meaningful ranges of results,” adds co-author Dr. Karl T. Bates of the University of Liverpool.

Calculating the masses of the resulting virtual T. rex herd yielded some exciting surprises. For instance, T. rex appears to have been significantly heavier than previously believed. The Field Museum’s SUE skeleton, which is the largest and most complete T. rex skeleton known, weighed in at over nine tons. “We knew she was big but the 30 percent increase in her weight was unexpected.” says Makovicky.

The new mass estimates also alter understanding of T. rex biology. The higher mass estimates for the larger specimens and a lower one for the smallest individual indicate even faster growth than was proposed in a landmark study just five years ago.

According to lead author Hutchinson, “We estimate they grew as fast as 3,950 pounds per year (1790 kg) during the teenage period of growth, which is more than twice the previous estimate.”

Funding for this study came from the National Environment Research Council (UK) and The Field Museum.

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