Geoscience Reference
In-Depth Information
gistsafewinsightsongastrolithresidencetimesafterdeath,anddifferencestokeep
in mind for a dinosaur carcass that stayed on land or ended up in a body of water.
Nevertheless, before such experiments, so many uncertainties about dinosaur
gastroliths caused paleontologists to reach for the only weapons that made sense
for handling such a desperate situation: lasers. As most people know, but most cats
do not, lasers use amplified beams of light that maintain nearly the same diameter
over long distances. Like all light, though, laser beams can be bent (refracted) or
bouncedback(reflected). Thesepropertiesoflightarethenapplicable tomeasuring
the degree of polish on a surface. Very simply, less polish causes laser light to scat-
termore,whereasmorepolish,suchasamirrormighthave,causesittoscatterless.
Howthesepropertiesoflaserlightcouldbeappliedtodinosaurgastrolithswas
thus related to one of the problems with identifying gastroliths outside of dinosaur
bodies. Smooth, lustrous surfaces on rocks are not necessarily the result of being
inside a dinosaur gut. Instead, such surface textures could be attributed to all sorts
of natural, non-biological processes, such as wind and water erosion. Could laser
reflectance detect the differences between rocks polished by wind or water versus
dinosaur viscera?
Sointheearly1990s,paleontologistKimManleytookalookatthedifferences
of laser-generated light scattering on genuine gastroliths, which were taken directly
from a sauropod skeleton (
Diplodocus
), wave-rounded rocks from beaches, and
river-rounded rocks. All three rocks had some degree of polish to them, but pale-
ontologists assumed that gastroliths, having spent time grinding up food in a di-
nosaur's crop, proventriculus, or gizzard, and subjected to stomach acids, were the
most polished.
So science struck with a blow delivered at the speed of light. It turned out that
some beach rocks were just as polished as the gastroliths, although both of these
were more polished than river rocks. This technique was refined in a 1994 study by
other scientists who looked at gastroliths from much more recently dead avian di-
nosaurs,moasfromNewZealand.Theselarge,extinctflightless birdslivedonboth
