Thursday, August 25, 2011


Fusulinids are extinct single-celled organisms called protists that lived from the Silurian to the Permian. Most fusulinids were about the size of a grain of rice, but some were up to two inches long. They had a hard wall that protected the cell inside.

Some fusulinids are so similar in shape that scientists have to use a cross section of the fossil to identify them.

Fusulinids probably lived in clear water and may have lived on reefs.

Fusulinids are very large and complex for single-celled life, which is usually microscopic. Fusulinids are marker fossils, which means by looking at the fusulinids in a rock formation, scientists can tell how old the rock is.

Note: Edited 8/31/11 to remove the word "animal" and replace it with "organism." Fusulinida was a protist, not an animal.


  1. Are there any living single-celled animals that aren't parasites?

  2. Isn't multicellularity a requirement of being classified as an animal? I would have thought this to be a protist...

  3. Those are huge for single cells! I had no idea single-celled animals could be that big--I thought they'd fall apart, for some reason. But apparently they were common enough to be a reliable way of dating rocks. Huh.

    I really like your blog, by the way.

  4. @Anonymous: Thank you for telling me about the error. I accidentally said "animal," but I knew it wasn't actually an animal. You're right, it's a protist. I corrected it.

  5. Please keep leaving your blog up! Your pages are often the best references for folks I'm introducing these topics to :)