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Waldron Trilobite (Silurian)


ClearLake

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I have a partial trilobite cephalon that I collected from the Waldron Shale spoils piles at Falls of the Ohio State Park.  Since it is not directly from the quarry wall, there is some uncertainty in the stratigraphy, but it is likely Waldron or the overlying Louisville Ls. both of which are right near the border between Lower and Upper Silurian.  Hopefully there is enough here to give a shot at an ID.  The best I can do is say it could be Metopolichas breviceps but there appear to be some differences.  Hopefully someone like @Kane or @piranha or @Ken K can see enough here to have an opinion.  If not, "Trilobite Head" it will be called.  Thanks for any help.

 

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Here it is enhanced a bit hopefully so you can see it better.  You can see by the scale that it is under 1 cm wide.

 

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My stab at an ID initially came from Halls 1879 publication on the Waldron.  Below I have my specimen between the figure out of Hall (on the right) and an example of one from the American Museum of Natural History website (left).  The AMNH site says this specimen is the only known complete example which just adds to my doubt on the ID, but I have not found a more common, better match.

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And lastly, here is a zoom in of the cephalon to hopefully show the small bumps covering it.

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Thanks again for any help.

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    Tim    -  VETERAN SHALE SPLITTER

   MOTM.png.61350469b02f439fd4d5d77c2c69da85.png      PaleoPartner.png.30c01982e09b0cc0b7d9d6a7a21f56c6.png.a600039856933851eeea617ca3f2d15f.png     Postmaster1.jpg.900efa599049929531fa81981f028e24.jpg    VFOTM.png.f1b09c78bf88298b009b0da14ef44cf0.png  VFOTM  --- APRIL - 2015  

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Definitely not from the Waldron Shale.

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Maybe Arctinurus that has those more rounded bullar lobes?

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According to the lichid whisperer: Lichas breviceps is a good match. Sometimes incorrectly assigned to Metopolichas following Weller 1907.

 

Thomas & Holloway 1988 placed it back within Lichas from the original description of Lichas breviceps Hall 1863.

 

 

Hall, J. 1863
Notice of some New Species of Fossils from a Locality of the Niagara Group

in Indiana, with a List of Identified Species from the same Place.  
Transactions of the Albany Institute, 4:195-228  PDF LINK

 

Thomas, A.T., Holloway, D.J. 1988
Classification and Phylogeny of the Trilobite Order Lichida.
Philosophical Transactions of the Royal Society of London, Series B 321:179-262  PDF LINK


Weller, S. 1907
The Paleontology of the Niagaran Limestone in the Chicago Area: The Trilobita.
Natural History Survey, Chicago Academy of Sciences, 4(2):163-281  PDF LINK

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image.png.a84de26dad44fb03836a743755df237c.png

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37 minutes ago, piranha said:

According to the lichid whisperer

Now there is a title not many people can claim!!  I like that!

 

38 minutes ago, piranha said:

Lichas breviceps is a good match. Sometimes incorrectly assigned to Metopolichas following Weller 1907.

 

Thomas & Holloway 1988 placed it back within Lichas from the original description of Lichas breviceps Hall 1863.

Thank you for that diagnosis and more importantly, thanks for the updated systematics and the links to references that go along with that.  I love reading those older reports, but sometimes have trouble finding them. I will switch the name back to Lichas in my files.

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17 hours ago, connorp said:

Definitely not from the Waldron Shale.

Yes, I should have said Waldron Shale Formation as this clearly is in a small chunk of limestone.  Personally, having only collected out of the in situ Waldron at one small locality, I can't swear that this definitely looks like a Waldron Fm. limestone, which is why I indicated it could be from the overlying Louisville Ls.  Now that I am more confident in the ID, I can look to see if this genus is known from the Louisville Fm.  

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