Unusual Trilobite Crinoid Association

Today’s photograph is of an unusual association of an odontopleurid trilobite and a diplobathrid crinoid that was collected from the Ordovician of Kentucky.

The trilobite(Acidaspis sp) is seen on the top most brachial of the crinoid(Reteocrinus sp.), in the photograph.

I am still trying to determine if the assemblage represents thanatocoenosic(death assemblage) preservation of a community, or post mordem predation by the trilobite, and then preservation.

Anyone have any thoughts?


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13 Responses to “Unusual Trilobite Crinoid Association”

  1. Fossil Detective Says:

    I wonder if the trilobite was hiding in the remains of the fallen crinoid? Is the cephalon still attached to that trilobite fossil?

    Small trilobites from that time appeared to have hid among bryozoans as shown by the images at this web page:


  2. Roy Says:

    That’s a great one.

    Often in the Helderberg of South NY you can find them within the same beds, but rarely together. Most of our Helderberg represents a death assemblage, so I would learn towards the previous commenter’s thoughts of the trilobite hiding.

    • Solius Symbiosus Says:

      Hi Roy. The trilobite could be hiding, but I am unfamiliar with this type of preservation among the odontopleurids and crinoids. And, if it was hiding, did it seek refuge after the event that killed the crinoids?

      I should clarify- this piece is from an outcrop that has produced numerous Reteocrinus sp.(>100), and one pinnate that I haven’t identified(probably Archeocrinus sp), and several trilobites… some in close association with the crinoids.

      Too, less that a meter above the “garden”, the lithology abruptly changes to a calcarenite with tidal sequences. Something weird was going on that killed the crinoids. Perhaps, it is related to the siesmites that are also found nearby???

  3. Solius Symbiosus Says:

    The cephalon on this one isn’t attached, but I have found a few complete ones from the same outcrop.

    I have wondered the same… years ago I pulled a Gravicalymeme molt from beneath a stromotoporoid. There is little data to suggest that these critters hid during the vulnerable stages of ecdysis, but that is probably because the problem hasn’t been properly studied.

    Frank Ettensohn recently showed me a brachiosponge that had 3 calyminids “hiding” on the underside.

    Too, from this outcrop, I have found what appears to be the remains of a trilobite in the living chamber of an othocerid cephalopod. So, these little critters had good reason to seek shelter.

  4. More Seismites, and some fossils « Swimming The Ordovician Seas Says:

    […] that has been producing large numbers of crinoids, and other interesting oddities(like this and this). But, that morning I wasn’t having much luck finding anything. Though, as I was packing up […]

  5. crinoids « Swimming The Ordovician Seas Says:

    […] In a bed about a meter below the contact, numerous diplobathrid crinoids are found… some of which are intimately associated with odontopleurid trilobites. […]

  6. ritaroberts Says:

    Oh dear I wish I could remember all the technical terms for these fossils.The trilobites, the brachiopods crinoids and trace fossils are my favourites.However if they were running around now I would run a mile,but they fascinate me because they have turned to stone and leave us so much history.

  7. ritaroberts Says:

    Thanks for yur apologies but dont worry other people understand your technical terms anyway and its just a hobby for me even though I did a short open university geology course on line I find it all hard to grasp. I will have to do a refresher course.

  8. ritaroberts Says:

    Thankyou so much for your offer of help I might just take you up on that at some point. Especially when I begin my refresher course which will be after Xmas now. Thanks again.

  9. John Says:

    I just found 3 Meadowtownella ( primaspis ) on 3 different Iocrinus (all found within a square meter). I’m also curious as to the meaning of this assemblage…

  10. John Says:

    Actually, I just found a fourth one, this one being on the very tip of the anal tube.Also, this last one was found on a different layer ( in situ ).

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