Research paper Direct UeTh dating of vertebrate fossils with minimum sampling destruction and application to museum specimens Gilbert J. Price * , Yue-xing Feng, Jian-xin Zhao, Gregory E. Webb School of Earth Sciences, The University of Queensland, St. Lucia 4072, Queensland, Australia article info Article history: Received 18 February 2013 Received in revised form 30 June 2013 Accepted 15 July 2013 Available online 23 July 2013 Keywords: U-series dating Museum specimens Fossil vertebrates Megafauna Quaternary abstract Although vertebrate fossils are commonly abundant in museum palaeontological collections, they are only rarely accompanied by contextual data (e.g., stratigraphic and taphonomic information) that allow them to be placed independently into reliable temporal frameworks critical for testing significant evolutionary and extinction hypotheses. Moreover, where critical samples do exist in such collections, sampling for direct geochronological analyses becomes a significant concern, especially where such sampling is destructive in nature. Here we apply a direct fossil dating, micro-drilling sampling approach that minimises damage to and destruction of precious museum specimens. We carried out a systematic UeTh dating study (n ¼ 28 ages) of an isolated museum specimen of the extinct Palorchestes azael (megafaunal ‘marsupial tapir’) originally collected in 1977 from Tea Tree Cave, Chillagoe, north- eastern Australia. We obtained 21 UeTh ages and constructed 230 Th-age profiles across three teeth exposed in cross-section, using micro-drilling and thermal ionisation mass spectrometry. Individual sample masses were as little as 0.18 mg (U concentration 33e82 ppm), meaning that the sampling resulted in only minimal destruction of the specimen. The results show no evidence of U leaching, suggesting that the dates represent reliable minimum ages. For independent age control, we also dated calcite that had encrusted the sample (thus, providing a minimum age; n ¼ 6) and an older calcite clast that had been reworked into the surrounding breccia at the time of burial (thus, providing a maximum age; n ¼ 1). UeTh ages of the teeth are older than the calcite overgrowths and younger than the reworked calcite, consistent with their demonstrable relative age relationships. Collectively, the results unequivocally bracket the age of the fossil between 199.1  8.9 ka and 137.4  1.1 ka (2s), adding another rare datum to inform the timing and geographic distribution of last occurrences of the species. The benefits of our dating approach of museum fossil specimens are threefold: 1) it is minimally destructive even compared with laser-ablation method; 2) the use of U vs. apparent age approach allows direct testing for potential U leaching as occasionally seen in fossil dating; and 3) the combination of fossil and associated speleothem dating provides the most robust means of securely bracketing the age of fossils that lack firm stratigraphic control. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Worldwide terrestrial ecosystems of the Pleistocene were dominated by large-bodied mammals, birds, turtles and lizards. The loss of many such animals, commonly referred to collectively as the ‘megafauna’ (e.g. mammoths and sabre-tooth cats), occurred during the late Pleistocene possibly as a result of anthropogenic influences and/or climate change, although the timing and mech- anisms of the extinctions remain controversial (Grayson and Meltzer, 2003, 2004; Fiedel and Haynes, 2004; Wroe and Field, 2006, 2007; Brook et al., 2007; Stuart and Lister, 2011; Wroe et al., 2013). Development of reliable, spatially and temporally-constrained palaeoecological models for each extinct megafaunal species is critical for determining the nature of the losses. Geochemical and isotopic techniques play an ever-increasing role in the generation of the key data crucial for testing extinction hypotheses. Aside from direct radiometric dating of the deposits that contain vertebrate fossils: carbon isotopes can inform the dietary preferences of megafaunal species (Feranec et al., 2009; Montanari et al., 2013); 87 Sr/ 86 Sr signatures in teeth and bones can aid investigation of the migratory patterns of megafauna (Hoppe and Koch, 2007; Widga et al., 2010); and trace element analyses can inform in- terpretations of the fossilisation processes and the potential for * Corresponding author. Tel.: þ61 7 3346 9758. E-mail address: g.price1@uq.edu.au (G.J. Price). Contents lists available at ScienceDirect Quaternary Geochronology journal homepage: www.elsevier.com/locate/quageo 1871-1014/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.quageo.2013.07.003 Quaternary Geochronology 18 (2013) 1e8