Thectardis
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Thectardis is an Ediacaran triangle shaped fossil. Specemins have been found in beds dated at 575 and 565 mya. The original organism was an elongated cone, with its point embedded into the microbial layer growing on the sea bed. The height of the triangle is up to 16.5 cm. The smallest triangles are 26 mm long. The diameter to height ratio of the orgnanism is roughly constant in each location at 1 to 3 in the new beds, and from 1 to 2.5 in the older beds. The constant ratio suggests that it grows by adding to its body at the circle or base of the cone. The triangle has a raised margin about a quarter of the width of the triangle. The interior either is a blank, depressed, or has some vague transverse arkings. The impression occurs in the upper bed rather than the lower surface. Current has bent the triangles in the same direction, and where they fall on top of other objects they flex over the top. This demonstrates that they were standing up on their tips originally, rather than already lying down and arranged at random. It is a bit of a mystery how the organism was attached to the sea bed, as there is no holdfast.
The bacteria growing on the sea floor may have made a firm enough mat so that the triangle stuck in it like a needle in a pin cushion.
It has been found at two places on Mistaken Point Newfoundland.
One species described is Thectardis avalonensis. The meaning of the name derives from the Greek word thectos meaning sharp-pointed, and ardis which means arrow-point. The name only coincidently contains the term tardis. The species name comes from the Avalon Peninsula. It was originally described by Matthew Clapham, Guy Narbonne, James Gehling, Carolyn Greentree and Michael Anderson in 2004. The organism is probably an animal, but not much more is known about its relationships.
[edit] References
- Clapham, Matthew E, Narbonne, Guy M, Gehling, James G, Greentree, Carolyn and Anderson, Michael M. 2004. Thectardis avalonensis: a New Ediacaran Fossil from the Mistaken Point Biota, Newfoundland. in Journal of Paleontology 78:6 (November 2004). pp. 1031–1036
