Wooster’s Fossil of the Week: the classic bioclaustration (Upper Ordovician of Ohio)

We’re looking at two fossils above. One is the bryozoan Peronopora, the major skeletal structure. The second is the odd series of scalloped holes in its surface. These are a trace fossil called Catellocaula vallata Palmer and Wilson 1988. They at first appear to be borings cut into the bryozoan colony. Instead they are holes formed by the intergrowth of a soft-bodied parasite with the living bryozoan colony. This type of trace fossil is called a bioclaustration. We gave it the Latin name for “little chain of walled pits”.

My good friend Tim Palmer and I found this specimen and many others in 1987 as we explored the Upper Ordovician Kope Formation in the Cincinnati region. We were collecting bioeroded substrates like hardgrounds and shells, and these features were clearly different from the usual borings. They do not actually cut the bryozoan skeleton, for one thing. For another it is apparent that the bryozoan growth was deflected around whatever sat in those spaces. Tim and I called this kind of interaction “bioclaustration”, meaning “biologically walled -up”.
Catellocaula vallata on the Upper Ordovician bryozoan Amplexopora. Note that the scalloped holes have more lobes than those seen in the lead image. This may mean it was a different species of infesting soft-bodied organism.

The infesting parasite on the bryozoan colony was itself colonial, consisting of small clusters connected by extended stolons. The bryozoan grew around the parasite, roofing over the stolons and making walls on the margins of the clusters. We think the parasite was a soft-bodied ascidian tunicate like the modern Botryllus. If true, it is the earliest fossil tunicate known.

This closer view of C. vallata shows the scalloped margins of the pits and the horizontal connections between them.

Another specimen of C. vallata. This view shows the flat floors of the bioclaustration features.

Acetate peels cut longitudinally through the bryozoan and bioclaustrations. On the left you can see that the bryozoan zooecia (long tubes) were deflected sideways as they grew. On the right is a tunnel connecting two pits, with bryozoan zooids forming the roof. (From Palmer and Wilson, 1988.)


Bromley, R.G., Beuck, L. and Taddei Ruggiero, E. 2008. Endolithic sponge versus terebratulid brachiopod, Pleistocene, Italy: accidental symbiosis, bioclaustration and deformity. Current Developments in Bioerosion, Erlangen Earth Conference Series, 2008, III, 361-368.

Palmer, T.J. and Wilson, M.A. 1988. Parasitism of Ordovician bryozoans and the origin of pseudoborings. Palaeontology 31: 939-949.

Tapanila, L. 2006. Macroborings and bioclaustrations in a Late Devonian reef above the Alamo Impact Breccia, Nevada, USA. Ichnos 13: 129-134.

Taylor, P.D. and Voigt, E. 2006. Symbiont bioclaustrations in Cretaceous cyclostome bryozoans. Courier Forschungsinstitut Senckenberg 257: 131-136.

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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5 Responses to Wooster’s Fossil of the Week: the classic bioclaustration (Upper Ordovician of Ohio)

  1. Jeff Bowen says:

    You’re throwing the word “parasite” around an awful lot there, DW. I don’t know you to be an imprecise man with words under any circumstances so I pulled up your 1988 paper (Palmer, T.J. and Wilson, M.A. 1988. Parasitism of Ordovician bryozoans and the origin of pseudoborings. Palaeontology 31: 939-949.) and read the discussion on the use of the term “parasite” and the assumptions implied thereby. Your reasons for using that word are so thoroughly and explicitly laid out in that paper too! However, by the definition in that 1988 paper, wouldn’t EVERY encrusting competitor on a still-living sclerozoan be considered a parasite whether we can see evidence of it reflected in their scleratic fossils or not?

    I don’t normally think of the guy on top in the race for elbow room in a reef as a parasite just because his feet are planted on someone else’s head. False but conveniently illustrative implications of cephalization (and pedi… ization…? and cubitization…? Yay for making up Latin-ish words :-D) in reef-building invertebrates aside, isn’t that just simple competition rather than parasitism? Would it not be a bad idea to label evidence of competition involving sclerozoans as parasitism just because someone always loses and someone always wins in a competition and sclerozoans, by definition, make great places to glue your “feet”?

    You’ve been doing this for more decades than I have been alive and you never stop thinking. I am going to assume your understanding of these interactions are much more nuanced and well-thought-out than my simple attack here. Also, while I’m not terribly precise with my own word choices or definitions, I’m married to a soon-to-be Doctor of Philosophy… IN PHILOSOPHY! I’ve picked up the habit of nitpicking others’ word choices and definitions since that’s a lot of what philosophers seem to do 😉 Don’t tell Kalyn, Kreuzman, or Garrett Thompson I said that!

    Hmm, it seems my tendency toward wanton verbosity got the better of me again…

  2. Mark Wilson says:

    Hello Jeff! I am very pleased to get such a thoughtful response from you. It is not “wanton verbosity” at all! Tim Palmer and I discussed the “parasitic” nature (or not) of this bioclaustration many times. Our conclusion was that the tunicate (if that’s what what was) resided on and eventually in the host and likely both sucked up some of the same nutrient stream and certainly blocked a significant number of bryozoan zooids from functioning. It is indeed a kind of competition, but the residency in and on the host tissues pushed us over into the parasite category.

    Is Kalyn almost done with her PhD? Good for her. I can only imagine the precision she has had to exercise with her words over the past few years.

    Hope you are doing well!

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  4. Ron Fine says:

    Mark, You have given one name, but noted that the two specimens may represent different species. I think I have found three types (and a couple oddballs). I believe I am seeing differences in number of lobes, size, branching pattern, colony density, and host bryozoan. Should you or someone else engage in further study of these, I have a lot of properly curated specimens that I would gladly donate.

  5. Mark Wilson says:

    Hi Ron! I have no doubt that you have a spectacular collection of these structures, enough to start a re-evaluation of Catellocaula. The original name is an ichnogenus and ichnospecies, as you know, so there are subtle differences between criteria for them and those for biological species. An even more interesting issue is whether such bioclaustrations should get trace fossil status at all. Catellocaula may be an excellent substrate, so to speak, for exploring not only this particular phenomenon, but also the question of nomenclatural (and thus conceptual) status of such fossils. Let me get through this semester (which may be a close-run thing!) and then we can talk about doing something together. Can you ask me again by email in December? I’d love to see your specimens. Thanks!

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