Wooster’s Fossil of the Week: A honeycomb coral (Upper Ordovician of southern Indiana)

Polygons are common in nature, whether in two dimensions as desiccation cracks or in three dimensions as with columnar basalt. They result from “closely-packed” disks or tubes. The honeycomb coral (Favosites Lamarck 1816) is one of the best fossil examples of hexagonal packing.

Favosites appeared in the Late Ordovician (about 460 million years ago) and went extinct in the Permian (roughly 273 million years ago). It consists of a series of calcitic tubes (corallites) packed together as closely as possible, thus the resemblance to a honeycomb. The corallites share common walls with each other. They were occupied by individuals known as polyps that were much like today’s modern coral polyps. They had tentacles that extended into the surrounding seawater to collect tiny prey such as larvae and micro-arthropods. (I’m confident here because we actually have fossils showing the soft polyps themselves.)

A, Portion of the corallum of Favosites favosa. B, Portion of four corallites of Favosites gothlandica, enlarged, showing the tabulae and mural pores. (From H.A. Nicholson (1877): "The Ancient Life History of the Earth A Comprehensive Outline of the Principles and Leading Facts of Palæontological Science.")

As you can see in the drawings above, the corallites are distinguished by internal horizontal partitions called tabulae and holes in the walls termed mural pores. These pores most likely allowed internal soft tissue connections between the polyps so that they could share digested nutrients.

Thin-section of Favosites from the Upper Ordovician of southern Indiana. Note the gaps in some corallite walls. These are mural pores.

Favosites as a genus has a very long history. It was named by the famous French natural historian and war hero Jean-Baptiste Lamarck. It is a favorite in paleontology courses because it is so easily recognized.

About Mark Wilson

Mark Wilson is a Professor of Geology at The College of Wooster. He specializes in invertebrate paleontology, carbonate sedimentology, and stratigraphy. He also is an expert on pseudoscience, especially creationism.
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26 Responses to Wooster’s Fossil of the Week: A honeycomb coral (Upper Ordovician of southern Indiana)

  1. Stephanie Jarvis says:

    These blog entries make me miss paleo!

  2. Mark Wilson says:

    Me too, Stephanie! Thanks for reading them.

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  5. Jess says:

    Hi Dr. Wilson,
    I found this blog through a google image search of this colonial coral Favosite sp. as I was trying to ID a fossil I found. I explored a little bit of your blog and I love it! Especially tackling the pseudoscience in the world… so important today. I have met so many bigfoot believers in my social circles, people that I respect a lot, and I am just so refreshed to see that you’re learning about them and keeping a rational mind. I just love your blog, very very important stuff here.
    Thanks for keeping it active.
    Jess

  6. Mark Wilson says:

    Thank you very much for your enthusiasm and kind words, Jess!

  7. Stephanie Moore says:

    I have found 3 of these in my area. 2 small last summer at a favorite swimming hole and a nice sized 1 in the rocks at mcdonalds…really! I didn’t know what they were at first but I knew they were special. Love seeing all the other specimens.

  8. Mark Wilson says:

    Thanks, Stephanie. Keep up the good work!

  9. Veronica Pheasant says:

    I also found one of these about 15 years ago on our beach I was flipping over rocks looking for crayfish and I flip this thing over and I was like what kind of rock is this? Realizing it had to be some type of coral I set out to look for an answer and a science teacher at school said it was 6 million year old piece of coral. I am in the southern half of Michigan just south of Flint north of Detroit for my understanding there are more of these in Lake Michigan just north of Chicago and some of the universities there have done studies on them and went into Lake Michigan and look for them but that’s about the most I found our lake is a man-made lake and was once land and they judged it out to make more channels on the lake I’m assuming this was dug up about 200 years ago and left on the shoreline. I left it at that but a couple years ago I started getting more and more into rocks and gems and stones and I posted it again today in a rock and mineral group I’m in send him so far only got one response is I feel like I’m the only one who’s excited about this piece of coral I have. The response did give me a correct name and I looked it up and it led me to your blog it is really quite big about the size of my hand a little smaller and I’m fascinated by the tiny little levels inside of it which I call Apartments LOL thanks for your article here I’ve enjoyed reading it.

  10. Mark Wilson says:

    Hi Veronica:

    You can send me a photo of your fossil coral (mwilson – at – wooster.edu). I can at least tell you it is MUCH older than 6 million years!

  11. Natalya says:

    Yesterday I found, I think, a miracle of nature. I’m just overwhelmed with joy. I am not a professional, I just really love crystals, stones, etc. Having sat on the Internet, I realized that this miracle is favosite. It looks like a honeycomb, sparkles beautifully from the inside. And it looks like a figurine. Of course I would like to know how old he is .. Thank you for creating such a forum !

  12. Mark Wilson says:

    Hi Natalya: Glad you find these fossil resources useful! Thank you for your kind words. If you want more information on the fossil you found, I may be able to help. Just email an image of the fossil to mwilson -at- wooster.edu

  13. Natalya says:

    I will do it with pleasure. I would be grateful if you send any information.

  14. Elizabeth says:

    My husband recently found one of these and I am trying to determine if it is in fact a honeycomb fossil and get more information about it.

  15. Mark Joegensen says:

    Thanks for the information. I routinely go out on Lake Michigan near Manitowoc Wisconsin and this year I’m finding more coral. I’ve found 4 pieces so far this year. Does the high water level of the lake have anything to do with me finding more coral or is that just a coincidence?

  16. Mark Wilson says:

    Hi Mark: I know that higher lake levels mean more shore erosion, so this probably means fossils are weathered out at a faster rate. Have fun! Mark

  17. Pat McCabe says:

    Are Petoskey Stones favosites?

  18. Mark Wilson says:

    Close, Pat, but Petoskey stones are rugose corals.

  19. Greg Cohen says:

    I found a very similar piece of Tabulate coral in middle Tennessee recently. It seems to be a silicified pseudomorph of honeycombed coral. I cleaned it and it appears to be made of quartz. I acid etched off the limestone around it and the piece is even more beautiful.

    Could you confirm it’s the same species, Favosites.

  20. Mark Wilson says:

    Thanks for sending the photos, Greg. Indeed, you have a very nice example of the tabulate coral Favosites.

  21. Nolan Snyder says:

    Hi! My name is Nolan. I’m 9 years old. I found a rock just like this at my grandparent’s creek in Indiana. I thought it was a part of a bee hive. I’m glad I found your website and what my rock is.

  22. Mark Wilson says:

    I saw a picture of your fossil, Nolan. It is indeed a honeycomb coral from an ancient sea. Good work!

  23. Elizabethq says:

    Hello Mr. Wilson,
    I’m happy to have found my way to this “Fossil of the Week” article. I found a beautiful piece of what I believe is honeycomb coral, but it’s somewhat more unusual that any picture I’ve found on-line. An e-mail with photos is on it’s way to you. Thank you for your kind generosity to help a novice like me.

  24. Mark Wilson says:

    I received your email and answered, Elizabeth. You indeed have a beautiful fossil Favosites coral.

  25. Maggie Mullins says:

    Thanks for all the fantastic information! My 5 year old and I just found two pieces of honeycomb coral in someone’s driveway gravel. He was so excited to find a fossil.

  26. Mark Wilson says:

    Thanks for this note, Maggie. Sounds like you’re raising a future paleontologist!

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