New Mexico Geological Society Annual Spring Meeting — Abstracts

3D visualization of x-ray computed tomography (CT) has revolutionized the study of paleontology over the last decade by allowing paleontologists to gain essential insights into the anatomy, development and preservation of important specimens. Neutron computed tomography (NT) is an exciting new frontier in 3D visualization that has only rarely been applied to vertebrate fossils. NT is based on the interaction of neutrons and the nuclei of materials and thus is able to reveal internal detail in fossils impregnated with dense minerals otherwise impervious to traditional CT, and can also be used to distinguish areas of distinct elemental or isotopic composition within fossils. We have applied high resolution CT and NT to two specimens, the skull of the holotype of the Cretaceous tyrannosauroid Bistahieversor sealeyi (NMMNH P-27469) and a nearly complete skull of the Paleocene phenacodontid “condylarth” mammal Tetraclaenodon puercensis (NMMNH P-69898) using the unique capabilities of the Los Alamos Neutron Science Center (LANSCE) at Los Alamos National Laboratory (LANL), New Mexico. To reduce attenuation of neutrons and x-rays a special carbon fiber composite, rather than plaster, support jacket was constructed to hold the Bistahieversor skull. The CT scan of the Bistahieversor skull used 10 MeV x-rays at 200 μm resolution. This is the highest resolution CT of an entire large (> 1m long) tyrannosauroid skull ever made. Both specimens were also scanned using high-energy or low-energy (thermal) neutrons. Preliminary NT results reveals details of the internal bone structure of both specimens not readily visible with CT, with no residual increased radiation level following the cool-off period. CT and NT showed that Bistahieversor possesses the extensive tympanic sinuses and elongate, tubular endocast that were once thought to diagnose only the largest-bodied, most derived tyrannosaurids like T. rex, whereas Tetraclaenodon has an endocast that was not as proportionally large, and overall more primitive, than the brains of modern placentals.

Grant Information: Work was undertaken on joint grants from the New Mexico Consortium, National Science Foundation (EAR 0207750 to TEW, EAR 1325544 and DEB-1654952 to TEW and SLB), Bureau of Land Management awarded to TEW and SLB, and led by NNSA programs to further development of advanced technique. LANL and the LANSCE accelerator facilities used in this work are funded under DOE contract DE-AC52-06NA25396.