Thectardis

taxobox
fossil_range=Ediacaran, 565-555 Ma
regnum = Animalia (?)
color = #taxobox color|animalia
phylum = "incertae sedis"
genus = Thectardis
genus_authority = Clapham "et al." 2004
species = "T. avalonensis"
species_authority = Clapham "et al." 2004

Thectardis is a triangular member of the Ediacara biota, dating from Ma|575|565. The organism took the form of an elongated cone with a central depression.

Morphology

The fossils take the form of a triangle with a central depression, suggesting that the original organism was conical.The diameter to height ratio of the organism is roughly constant in each location at 1 to 3 in the younger beds, and from 1 to 2.5 in the older beds. The constant ratio suggests that it grew by adding to its body at the base of the cone. The triangle has a raised margin about a quarter of the width of the triangle. The interior either is blank, depressed, or has some vague transverse markings. The impression occurs in the upper bed rather than the lower surface.

Occurrence

205 specimens of "Thectardis" are known, from two bedding surfaces, separated by 2 km and 10 million years at Mistaken Point, Newfoundland.

"Thectardis" bearing bedding surfaces also contain "Charnia" and "Ivesia".

Ecology

Water currents have bent the triangles in the same direction, and where they fall on top of other objects they flex over the top.The organism probably stuck to the microbial mats that bound the Ediacaran sea floor, standing on their tips like a pin in a pin cushion. They probably fed on suspended particles. As there is no evidence for a holdfast anchoring them to the sea floor, it remains a matter of speculation how they were attached.

Etymology

Thectardis is derived from the Greek "thektos", sharp-pointed, and "ardis", arrow-point. The specific name derives from the Avalon Peninsula, where it was found.

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