TRACKING STOLEN FOSSILS: A STUDY TO DETERMINE THE UTILITY OF RARE EARTH ELEMENTS AS A TOOL FOR VERTEBRATE FOSSIL PROTECTION

Although the Omnibus Land Management Act of 2009 provides harsher penalties to fossil poachers, no reliable, objective method exists to test whether or not a fossil bone was excavated from federal lands. Rare earth element (REE) fingerprinting is a potentially useful tool to match stolen bones to their original localities. REE are adsorbed onto bone apatite during fossilization, imparting a signature that is both independent of faunal type and reflective of pore water chemistry. Thus, as groundwater chemistry varies through time and space, associations of fossil bones will have different concentrations of the REE series. In this study, 62 samples of fossilized brontothere and tortoise remains were collected from three outcrops of the Eocene Chadron Formation located within Toadstool Geologic Park, northwest Nebraska. To understand the degree to which REE patterns vary between fossilliferous locations, three levels of statistical comparison were completed. Thirty-three in situ fossils were collected from an outcrop in the Big Cottonwood Creek Member. Through discriminant analysis and cladistical representation, we demonstrate that these samples can be matched to each of the three facies from which they were collected. These samples were then compared to fossils from two other areas of the park that lie within the Peanut Peak Member. Fossil samples from these three sites can be matched to their original location 85.5% of the time. On a much broader scale, we compared all the specimens collected from Toadstool Geologic Park to 81 samples previously collected in Badlands National Park and found that the fossil bones can be associated with their park of origin 98.6% of the time. These data suggest that REE fingerprinting can help to pinpoint the area from which a fossil was stolen when the specimen is compared to a database of catalogued fossil sites. When coupled with a sound understanding of the geology and taphonomy of bone beds, REE fingerprinting may become a useful addition to the toolbox of current law enforcement methods to protect fossil resources on federal lands.