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

Published online by Cambridge University Press:  20 May 2016

Matthew E. Clapham ,
Guy M. Narbonne ,
James G. Gehling ,
Carolyn Greentree  and
Michael M. Anderson
Matthew E. Clapham
Affiliation:
1Department of Geological Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada
Guy M. Narbonne
Affiliation:
1Department of Geological Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada
James G. Gehling
Affiliation:
1Department of Geological Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada
Carolyn Greentree
Affiliation:
41–249 Macdonnell Street, Kingston, Ontario K7L 4C4, Canada
Michael M. Anderson
Affiliation:
553 Sterling Crescent, St. John's, Newfoundland A1A 4J9, Canada
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Abstract

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.

Type
Research Article
Information
Journal of Paleontology , Volume 78 , Issue 6 , November 2004 , pp. 1031 - 1036
Copyright
Copyright © The Paleontological Society

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Footnotes

2

Present address: Department of Earth Sciences, University of Southern California, Los Angeles 90089, <clapham@usc.edu>

3

Present address: South Australian Museum, Division of Natural Science, North Terrace, Adelaide, South Australia 5000

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