Taxonomic assessment of the Trinil molars using non-destructive 3D structural and developmental analysis

Two molars recovered at Trinil, Java, have been the subject of more than a century of debate since their discovery by Eugène Dubois in 1891–92. These molars have been attributed to several ape and human taxa (including Pan and Meganthropus), although most studies agree that they are either fossil Pongo or Homo erectus molars. Complicating the assessment of these molars is the metric and morphological similarity of Pongo and Homo erectus molars, and uncertainty regarding their serial positions within the maxillary row. Here we applied non-destructive conventional and synchrotron microtomographic imaging to measure the structure of these molars and aspects of their development. Comparisons were made with modern Homo and Pongo maxillary molars, as well as small samples of fossil Pongo and Homo erectus molars. Root spread was calculated from three-dimensional surface models, and enamel thickness and enamel-dentine junction morphology were assessed from virtual planes of section. Developmental features were investigated using phase contrast X-ray synchrotron imaging. PaleoAnthropology 2009: 117−129. © 2009 PaleoAnthropology Society. All rights reserved. ISSN 1545-0031 Tanya m. smiTH Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, D-04103, Leipzig, GERMANY; and Department of Anthropology, 11 Divinity Avenue, Harvard University, Cambridge, MA 02138, USA; tsmith@fas.harvard. edu anTHony j. olEjniCzak Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, D-04103, Leipzig, GERMANY; and Grupo de Antropología Dental, Centro Nacional de Investigación sobre la Evolución Humana, Avda. de la Paz 28, 09004 Burgos, SPAIN; olejniczak@eva.mpg. de koRnElius kupCzik Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, D-04103, Leipzig, GERMANY; kornelius.kupczik@eva.mpg. de vinCEnT lazzaRi Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, D-04103, Leipzig, GERMANY; and Steinmann-Institut für Geologie, Mineralogie und Paläontologie, Nußallee 8, 53115 Bonn, GERMANY; and European Synchrotron Radiation Facility, 6 rue ules Horowitz, BP 220, 38043 Grenoble cedex, FRANCE; screetch20100@yahoo.fr joHn DE vos Department of Palaeontology, Nationaal Natuurhistorisch Museum Naturalis, P.O. Box 9517, NL-2300 RA Leiden, THE NETHERLANDS; vos@naturalis.nnm. nl oTTmaR kullmER Department of Paleoanthropology and Messel Research, Senckenberg Research Institute, D-60325 Frankfurt a.M., GERMANY; ottmar.kullmer@senckenberg.de fRiEDEmann sCHREnk Department of Vertebrate Paleontology, Institute for Ecology, Evolution, and Diversity, Johann Wolfgang Goethe University, Frankfurt a.M., GERMANY; schrenk@malawi.net jEan-jaCquEs Hublin Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, D-04103, Leipzig, GERMANY; hublin@eva.mpg. de TEuku jaCob ‡ Department of Bioanthropology and Palaeoanthropology, Faculty of Medicin, Gadjah Mada University, Yogyakarta, INDONESIA paul TaffoREau European Synchrotron Radiation Facility, 6 rue ules Horowitz, BP 220, 38043 Grenoble cedex, FRANCE; paul.tafforeau@esrf.fr