Bone Density

Peter is 47% complete by ‘bulk’ or Bone Volume. This was calculated by T. rex expert Dr David Burnham from Kansas University’s Institute for Biodiversity and Natural History Museum, who is one of the world’s leading therapod paleontologists. Dr Burnham calaculated Peter’s completeness using the most scientifically accurate measurement, pioneered by the Field Museum in Chicago, home to “Sue” the most complete T. rex in the world.


As Dr Burnham writes, “The most rigorous approach to the way percentage is calculated, is to use bone density. Specimen completeness is calculated by assigning weighted percentage values to the bones. In this method, a femur carries more weight than a toe bone. This naturally has scientific value as well, since it recognizes the importance of one bone over another; we know that there are more pathologies identifiable in the larger bones than smaller ones, and so they are much more important from a scientific research perspective as well. 

Peter’s completeness as 47% by bulk, was calculated mathematically by computing the area of each individual bone represented using measuring software. Then Dr Burnham totaled the area of all the elements. A percentage was determined by comparing this total to the total area of a hypothetical 100% complete skeleton. This percentage was also calculated independently for both left and right sides of Peter. The side areas were then added to get a single area value to compare to the total area which was then expressed as the total percent completeness of the specimen. 

Sharing the science

We’re pleased to be able to share Preliminary Scientific Reports to help visitors who come to see these incredible T. rex understand more about them.

These reports are prepared by two of the world’s top therapod paleontologists, Dr David Burnham (University of Kansas Biodiversity Institute and Natural History Museum) and Dr John Nudds (Department of Earth and Environmental Sciences, University of Manchester), who have studied both Peter and Barbara in their university laboratories for many months. Their research has identified the unique pathologies of each specimen, such as the injury to Barbara’s leg and the marks on Peter’s leg. As these reports are preliminary, they’re not peer-reviewed yet.

It’s not standard practice for a museum to share this much information when a specimen is being exhibited for the first time, but with the benefactor’s agreement we’re keen to share the initial findings, to enhance the learning experiences that having these two specimens in our Museum provides for the people of Aotearoa New Zealand.

Updates to the Preliminary Scientific Reports will be an ongoing process and will most likely span decades, rather than years.