June 22, 2017 at 9:29 pm #24045
Not sure what this is. I collected it in a roadcut in southwestern Wisconsin. There was a trilobite on the rock and other Ordovician fossils.
Attachments:You must be logged in to view attached files.June 22, 2017 at 9:41 pm #24049Jack KallmeyerModerator
@julie-niederkorn The reddish object in the first two photos is the glabella (central part of the cephalon) of a trilobite. The third photo shows the pygidium of a trilobite. Sorry I can’t tell you what the species is.
JackJune 22, 2017 at 10:56 pm #24051Jeff NolderParticipant
Hi again, Julie -I think the pygidium is Flexicalymene meeki. The cephalon could be, as well, but there isn’t enough exposed for me to be sure. I’m glad you liked SW WI; hard to get good exposures here in the drifted area of SE WI.June 23, 2017 at 7:05 am #24052Jim ChandlerParticipant
The “Poka-dotted” fossils in photos 1&2 are bryozoans.
JimJune 25, 2017 at 12:49 pm #24062
That pygidium is definitely not Flexicalymene! Note in this photo how triangular Flexicalymene‘s pygidium is, and how it terminates with a prominent bulb on the median lobe with hardly any posterior margin. The pygidium you show has many segments and a broad posterior margin — features typical of order Proetida, not Phacopida (of which Flexicalymene is a member). I was not able to locate an Ordovician trilobite to match your image, but I’ve included below an image of a pygidium that more closely matches the features I see in yours. (This pygidium belongs to Dikelocephalus, which is certainly not the trilobite in your hand.)June 25, 2017 at 12:54 pm #24063
The cephalon appears to belong to some ceraurine trilobite. For example, here is Ceraurus. Note the glabellar lobes and how they’re connected to the other parts of the cephalon.June 25, 2017 at 12:56 pm #24064June 29, 2017 at 9:19 am #24128July 20, 2017 at 5:20 pm #24339
Julie @julie-niederkorn, you have opened my eyes! I was assuming the entire fossil to be a pygidium, but now I take your point that it comprises the whole thorax plus the pygidium. And that makes it an excellent match for the thoracopygidium of Thaleops ovata. It also helps explain the outline that appears anterior to the thorax: It’s a cross-section through the cephalon. I note especially the robust right gena. For comparison:
Congrats on your first complete trilobite, Julie 🙂July 20, 2017 at 7:07 pm #24340
Thank you! I am so excited to have found one!
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