The oldest biomarker molecules extracted directly from individual fossils are reported from Lower Mississippian (340-million-year-old) crinoids from Indiana. Here, as in many other well-preserved crinoid occurrences, crinoid specimens of the same species are preserved in calcite of different colors. Thus, the isolated biomarkers represent some attribute intrinsic to each species. Biomarker molecules are reported from three species that occur in the same sedimentary bed. Extracted molecules preserve a phylogenetic signal, with the two more closely related species having more similar biomarkers compared with a third, more distantly related taxon. These biomarker molecules resemble aromatic or polyaromatic quinones based upon ultraviolet visible light spectroscopy (UV-Vis), fluorescence excitation emission matrix fluorescence spectroscopy (EEMs), and electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), which are similar in structure to echinochromes, spinochromes, and gymnochromes that occur in living echinoderms. Results suggest that the preservation of diagnostic organic molecules is much more common that previously realized and that preserved organic molecules may provide an independent method to unravel phylogenetic relationships among echinoderms and, perhaps, other fossilized organisms.
Long-term east-west asymmetry in monsoon rainfall on the Tibetan Plateau
Adam M. Hudson (corresponding) and Jay Quade, Dept. of Geosciences, University of Arizona, Tucson, Arizona 85721, USA. Posted online 17 Jan. 2013;
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Geological Society of America