Wilson, Jonathan P. and Grotzinger, John P. and Fischer, Woodward W. and Hand, Kevin P. and Jensen, Sören and Knoll, Andrew H. and Abelson, John and Metz, Joannah M. and McLoughlin, Nicola and Cohen, Phoebe A. and Tice, Michael M. (2012) Deep-water incised valley deposits at the ediacaran-cambrian boundary in southern Namibia contain abundant treptichnus pedum. Palaios, 27 (4). pp. 252-273. ISSN 0883-1351 http://resolver.caltech.edu/CaltechAUTHORS:20120622-154623282
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Valley-filling deposits of the Nama Group, southern Namibia, record two episodes of erosional downcutting and backfill, developed close together in time near the Ediacaran-Cambrian boundary. Geochronological constraints indicate that the older valley fill began 539.4 ± 1 Ma or later; the younger of these deposits contains unusually well-preserved populations of the basal Cambrian trace fossil Treptichnus pedum. Facies analysis shows that T. pedum is closely linked to a nearshore sandstone deposit, indicating a close environmental or taphonomic connection to very shallow, mud-draped sandy seafloor swept by tidal currents. Facies restriction may limit the biostratigraphic potential of T. pedum in Namibia and elsewhere, but it also illuminates functional and ecological interpretation. The T. pedum tracemaker was a motile bilaterian animal that lived below the sediment-water interface—propelling itself forward in upward-curving projections that breached the sediment surface. The T. pedum animal, therefore, lived infaunally, perhaps to avoid predation, surfacing regularly to feed and take in oxygen. Alternatively, the T. pedum animal may have been a deposit feeder that surfaced largely for purposes of gas exchange, an interpretation that has some support in the observed association of T. pedum with mud drapes. Treptichnus pedum provides our oldest record of animals that combined anatomical and behavioral complexity. Insights from comparative biology suggest that basal Cambrian T. pedum animals already possessed the anatomical, neurological, and genetic complexity needed to enable the body plan and behavioral diversification recorded by younger Cambrian fossils.
|Additional Information:||© 2012 SEPM Society for Sedimentary Geology. Published Online: April 2012. We are grateful for support for this project from the Agouron Foundation. We thank Roger Swart and Wim Dewulf-Peijenborgh for essential logistic support, Cori Bargmann for discussion of behavioral biology, and Jennifer Griffes and Ralph Milliken for assistance with figure composition. SJ acknowledges funding from the Spanish Ministry of Science and Innovation through grant CGL-2008-0473 (co-financed by Fondo Europeo de Desarrollo Regional [FEDER]) This manuscript was improved with helpful comments from Cornel Olariu and an anonymous reviewer.|
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|Deposited By:||Jason Perez|
|Deposited On:||25 Jun 2012 14:59|
|Last Modified:||25 Jun 2012 14:59|
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