Skip to main content Accessibility help

Thectardis avalonensis: A new Ediacaran fossil from the Mistaken Point biota, Newfoundland

  • Matthew E. Clapham (a1), Guy M. Narbonne (a1), James G. Gehling (a1), Carolyn Greentree (a2) and Michael M. Anderson (a3)...


The Neoproterozoic Ediacara biota at Mistaken Point contains the oldest diverse Ediacaran assemblages and is one of the few known deepwater localities, yet the biota is dominated by endemic forms, nearly all of which remain undescribed. Thectardis avalonensis new genus and species, one of these endemic forms, is a cm-scale triangular fossil with a raised rim and a featureless-to-faintly-segmented central depression. More than 200 specimens occur on two bedding plane surfaces: the 565 Ma E surface and the 575 Ma Pigeon Cove surface, nearly 2,000 m lower in the succession. Morphological and taphonomic data suggest that the organism was an elongate cone that may have lived as a suspension-feeding “mat sticker” with its pointed base inserted into the microbially bound sediment. If true, Thectardis n. gen. would be the tallest-known mat sticker, reaching a maximum height of over 15 cm. Specimens display little ontogenetic change in length:width ratio, suggesting that Thectardis grew uniformly by incremental addition of material to its distal end. Morphological differences between specimens at two well-separated stratigraphic levels may have resulted from evolutionary or ecophenotypic variation.



Hide All
Anderson, M. M., and Morris, S. Conway 1982. A review, with descriptions of four unusual forms, of the soft-bodied fauna of the Conception and St. John's groups (late-Precambrian), Avalon Peninsula, Newfoundland. Third North American Paleontological Convention Proceedings, p. 18.
Anderson, M. M., and Misra, S. B. 1968. Fossils found in the Pre-Cambrian Conception Group of south-eastern Newfoundland. Nature, 220:680681.
Benus, A. P. 1988. Sedimentological context of a deep-water Ediacaran fauna (Mistaken Point, Avalon Zone, eastern Newfoundland), p. 89. In Landing, E., Narbonne, G. M., and Myrow, P. M. (eds.), Trace Fossils, Small Shelly Fossils, and the Precambrian–Cambrian Boundary. New York State Museum and Geological Survey Bulletin, 463.
Billings, E. 1872. On some fossils from the primordial rocks of Newfoundland. Canadian Naturalist and Quarterly Journal of Science, n.s., 6:465479.
Bowring, S. A., Myrow, P. M., Landing, E., and Ramezani, J. 2003. Geochronological constraints on terminal Neoproterozoic events and the rise of metazoans. NASA Astrobiology Institute General Meeting Abstracts, p. 113114.
Boynton, H., and Ford, T. D. 1995. Ediacaran fossils from the Precambrian (Charnian Supergroup) of Charnwood Forest, Leicestershire, England. Mercian Geologist, 13:165182.
Clapham, M. E., and Narbonne, G. M. 2002. Ediacaran epifaunal tiering. Geology, 30:627630.
Clapham, M. E., Narbonne, G. M., and Gehling, J. G. 2003. Paleoecology of the oldest-known animal communities: Ediacaran assemblages at Mistaken Point, Newfoundland. Paleobiology, 29:527544.
Dornbos, S. Q., and Bottjer, D. J. 2000. Evolutionary paleoecology of the earliest echinoderms: helicoplacoids and the Cambrian substrate revolution. Geology, 28:839842.
Durham, J. W. 1993. Observations on the Early Cambrian helicoplacoid echinoderms. Journal of Paleontology, 67:590604.
Ford, T. D. 1958. Pre-Cambrian fossils from Charnwood Forest. Proceedings of the Yorkshire Geological Society, 31:211217.
Friedman, G. M., and Sanders, J. E. 1974. Positive-relief bedforms on modern tidal flat that resemble molds of flutes and grooves: implications for geopetal criteria and for origin and classification of bedforms. Journal of Sedimentary Petrology, 44:181189.
Gehling, J. G. 1999. Microbial mats in terminal Proterozoic siliciclastics: Ediacaran death masks. Palaios, 14:4057.
Gehling, J. G., Narbonne, G. M., and Anderson, M. M. 2000. The first named Ediacaran body fossil, Aspidella terranovica. Palaeontology, 43:427456.
Jenkins, R. J. F., and Gehling, J. G. 1978. A review of the frond-like fossils of the Ediacaran assemblage. South Australian Museum Records, 17:347359.
Landing, E., Narbonne, G. M., Myrow, P. M., Benus, A. P., and Anderson, M. M. 1988. Faunas and depositional environments of the Upper Precambrian through Lower Cambrian, southeastern Newfoundland (field trip road log), p. 2732. In Landing, E., Narbonne, G. M., and Myrow, P. M. (eds.), Trace Fossils, Small Shelly Fossils, and the Precambrian–Cambrian Boundary. New York State Museum and Geological Survey Bulletin, 463.
Martin, M. W., Grazhdankin, D. V., Bowring, S. A., Evans, D. A. D., Fedonkin, M. A., and Kirschvink, J. L. 2000. Age of Neoproterozoic bilaterian body and trace fossils, White Sea, Russia: Implications for metazoan evolution. Science, 288:841845.
Misra, S. B. 1969. Late Precambrian (?) fossils from southeastern Newfoundland. GSA Bulletin, 80:21332140.
Misra, S. B. 1971. Stratigraphy and depositional history of late Precambrian coelenterate-bearing rocks, southeastern Newfoundland. GSA Bulletin, 82:979988.
Narbonne, G. M. 1998. The Ediacara biota: a terminal Neoproterozoic experiment in the evolution of life. GSA Today, 8(2):16.
Narbonne, G. M., and Gehling, J. G. 2003. Life after Snowball: The oldest complex Ediacaran fossils. Geology, 31:2730.
Narbonne, G. M., Dalrymple, R. W., and Gehling, J. G. 2001. Neoproterozoic fossils and environments of the Avalon Peninsula, Newfoundland. Geological Association of Canada Fieldtrip Guidebook B5, 100 p.
Seilacher, A. 1992. Vendobionta and Psammocorallia: Lost constructions of Precambrian evolution. Journal of the Geological Society (London), 149:607613.
Seilacher, A. 1999. Biomat-related lifestyles in the Precambrian. Palaios, 14:8693.
Waggoner, B. M. 1999. Biogeographic analyses of the Ediacara biota: A conflict with paleotectonic reconstructions. Paleobiology, 24:440458.
Wood, D. A., Dalrymple, R. W., Narbonne, G. M., Gehling, J. G., and Clapham, M. E. 2003. Paleoenvironmental analysis of the Late Neoproterozoic Mistaken Point and Trepassey formations, southeastern Newfoundland. Canadian Journal of Earth Sciences, 40:13751391.


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed