Produced
by the Population Genetics and Evolution class, Furman University |
The
Ediacaran: Kimberella |
Tribrachidium heraldicum,
meaning “Heraldic three arms” is a mysterious fossil (Waggoner
1994). It shows an abbreviated spiral pattern with three arms at varying
levels (Palaeos: Proterozoic). It was first discovered and named in
Australia by Martin Glaessner and Brian Daily in 1959, but Tribrachidium
can also be found in silliciclastic sediments in the White Sea, Russia,
and Ukraine. The most peculiar feature of Tribrachidium is
that it displays triradial symmetry, as opposed to bilateral symmetry
that most organisms display (Waggoner 1994). As illustrated in the picture
on the right, they are disc-shaped and are about 5 cm in diameter. Their
three curved arms extended from the center towards the edge of their
body. The arms were probably hollow, and it is speculated that they
could inflate or deflate as well. From the arms, loose filaments or
fleshy ridges extended to form the rest of the body (Absolute Astronomy).
Tribrachidium are thought to be related to either echinoderms
or cnidarians, however this is still under debate (Waggoner 1994). Some
also believe that it’s not a whole animal, but rather the holdfast
of one. Others argue that it is not an animal at all, but rather a protist
or a member of a now extinct kingdom of multi-cellular organisms (Trip
Atlas). Page by Matt Medlin |
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Tribrachidium fossil found in Australia. Waggoner, B. 1994. Vendian Animals: Tribrachidium. UC Berkeley. http://www.ucmp.berkeley.edu/vendian/tribrach.html |
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Absolute Astronomy. Tribrachidium. http://www.absoluteastronomy.com/topics/Tribrachidium Palaeos Proterozoic: The Proterozoic Era. The Vendobionta. http://www.palaeos.com/Proterozoic/Proterozoic.2.html Trip Atlas. Tribrachidium. http://www.tripatlas.com/Tribrachidium#References Waggoner, B. 1994. Vendian Animals: Tribrachidium. UC Berkeley. http://www.ucmp.berkeley.edu/vendian/tribrach.html |