Why Did T. Rex Have Such Small Arms?

During the recent experiments, researchers directed intense X-rays — about a million times more powerful than an X-ray at a doctor’s office — at the fossil.

They scanned an area about three inches square and one to two inches deep on both bones of SUE’s forelimb, which is about the same length as a human arm, but much more robust.

Based on the ways the beams scatter from the rock, researchers can reconstruct the locations of different anatomical elements in the bones and the tiny holes deep inside that were once blood vessels and cells.

“Understanding the fine internal morphology of the skeleton will give us clues about how the arm could move and what it was used for,” Soriano said.

Even bare bones contain hints at what they were used for in life. For example, the bones of birds are hollow and less calcified for flying, while heavier, denser bones might indicate bones were used for tasks of strength. Patterns revealed by these intense scans will give scientists more information to decode what SUE might have used her arms for.

The study was performed in collaboration with Paul Tafforeau of the European Synchrotron Radiation Facility in France. The collaboration began when he and Soriano met at a conference in Chicago as the only paleontologists-in-residence at X-ray light sources in the world.

“Paleontologists really love any high tech we can use,” Soriano said, “since it’s the closest we can get to time travel.”

The experiments took place at the X-ray Science Division’s beamline 2-BM. The arm was returned to display at the Field October 11 while the data is analyzed.

The Advanced Photon Source is a U.S. Department of Energy Office of Science User Facility operated by Argonne National Laboratory.

Contacts and sourcesL
Argonne National Laboratory