'Fattysaurus' or 'thinnysaurus'? How dinosaurs measure up with laser imaging

Karl Bates and his colleagues in the palaeontology and biomechanics research group have reconstructed the bodies of five dinosaurs, two T. rex (Stan at the Manchester Museum and the Museum of the Rockies cast MOR555), an Acrocanthosaurus atokensis, a Strutiomimum sedens and an Edmontosaurus annectens.

The team, whose findings are published in the Public Library of Science journal PLoS ONE today (19th February 2009), found that the smaller Museum of the Rockies T. rex could have weighed anywhere between 5.5 and 7 tonnes, while the larger specimen (Stan) might have weighed as much as 8 tonnes.

Acrocanthosaurus atokensis was a large predatory dinosaur that looked like T. rex but with large spines on its back and roamed the earth much earlier in the mid Cretaceous period, around 110M years ago. The team suggest Acrocanthosaurus probably weighed in at a similar mass to MOR555 and other medium sized adult T. rex at about 6 tonnes.

The Strutiomimum sedens, whose name means "ostrich mimic", lived alongside T. rex in the late Cretaceous period and probably weighed somewhere between 0.4 – 0.6 tonnes

The reconstruction of Edmontosaurus annectens, a plant-eating hadrosaur was based on a juvenile specimen, but still weighed in at between 0.8 – 0.95 tonnes. As adults, some hadrosaurs grew as big as T. rex, again living in the late Cretaceous period.

The team used laser scanning (LiDAR) and computer modelling methods to create a range of 3D models of the specimens, attempting to reconstruct their body sizes and shape as in life. The laser scanner images the full mounted skeleton, resulting in a detailed 3D model in which each bone retains its spatial position and articulation. This provides a high resolution skeletal framework around which the body cavity and internal organs such as stomach, lungs and air sacs can be reconstructed. This has allowed calculation of body segment masses, centres of mass and moments of inertia for each animal – all the information that is needed to analyse body movements.