Sunday, June 26, 2011


Tribrachidium was a strange genus of ediacara which has been found in Russia, Ukraine, and Australia. 

Tribrachidium has been described as a member of many groups. It probably lived on the bottom of the ocean filtering food. Like many animals from the Ediacaran Period, Tribrachidium was mysterious and little is known about it. 

Tribrachidium had trilateral symmetry, which means its three sides were alike. Tribrachidium's three arms were possibly hollow and could inflate and deflate themselves, possibly to move up and down in the water. It was about 2" or 5 cm. 

Tribrachidium is the only animal that has been discovered so far that is trilaterally symmetrical. So Tribrachidium may have been in its own group with no descendants. 


  1. Hi ABC. My seven year old son and I like your blog. What does Trilaterally Symmetrical mean?

  2. Wow. This blog is amazing.

    I did not know that any trilaterally symmetric organisms had ever evolved on Earth.

  3. Love the blog. Got you on my Googlereader and never miss a post.

  4. Hi ABC,

    I love your blog and have added it to my reading list. I did not know there had ever been a trilaterally symmetrical animal. That's especially interesting because most animals are bilaterally symmetrical, and some animals, like starfish, have higher-order symmetry, but nature skips over 3 in animals for some reason.

    I am learning a lot by reading this blog and I hope you continue to write about ancient life.


  5. Cool blog, ABC! Keep it up! I learn so much!

  6. @ChefDad Trilaterally symmetrical means something has three equal parts that are mirror images of each other. A creature with radial symmetry is one that if it's cut in half, each half is a mirror image of the other one.

  7. Thank you to all my readers!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

  8. Dear ABC, this is a wonderful blog. You may be interested to know that trilateral symmetry does exist among plants, but it's very rare. The Triangle Palm (Dypsis decaryi), for example, only grows in one small region of Madagascar.