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Mystery Devonian Trilobite from Nevada


MarcusFossils

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Hi all, 

 

I received this 2cm trilobite as a gift from a friend, who claims its from the Grass Valley, Lander County, Nevada. After a bit of reading, I'm fairly confident this means Nevada Limestone Formation. I can however only find references to Phacops, Proetus, Dalmanites and Phillipsia from this Formation..is this a Proetus sp?

 

Help appreciated :)

 

Marc 

IMG_20170630_204314~01.jpg

Website: https://www.instagram.com/paleo_archives/

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“It is by no means an irrational fancy that, in a future existence, we shall look upon what we think our present existence, as a dream.”

Edgar Allan Poe

 

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1 hour ago, MarcusFossils said:

I received this 2cm trilobite as a gift from a friend, who claims its from the Grass Valley, Eureka County, Nevada. After a bit of reading, I'm fairly confident this means Nevada Limestone Formation. I can however only find references to Phacops, Proetus, Dalmanites and Phillipsia from this Formation..is this a Proetus sp?

 

 

Phillipsiids occurred in the Carboniferous-Permian, certainly not with any dalmanitids or phacopids.  What paper had this info?

image.png.a84de26dad44fb03836a743755df237c.png

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15 minutes ago, piranha said:

 

 

Phillipsiids occurred in the Carboniferous-Permian, certainly not with any dalmanitids or phacopids.  What paper had this info?

Found this is a Google book, here's the relevant information:

 

Title Paleontology of the Eureka District
Volume 8 of Monographs of the United States Geological Survey
Author Charles Doolittle Walcott
Publisher U.S. Government Printing Office, 1884

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Website: https://www.instagram.com/paleo_archives/

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“It is by no means an irrational fancy that, in a future existence, we shall look upon what we think our present existence, as a dream.”

Edgar Allan Poe

 

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Remember to check more carefully when using the older literature.  There are a lot of updates since Walcott's work from the late 1800's.  Walcott wasn't sure if it was Phillipsia? or Brachymetopus?, and Phillipsia and Brachymetopus do not occur in the Devonian of North America, so we would have to cross-reference Hall's figures to try and and make a better determination.  In any event, Walcott only had a glabella, so that one really is a wild goose chase.  The "Phacops" in the report is probably Viaphacops claviger from the Lower Devonian Wenban Limestome in Eureka County.  

 

Back to the mystery trilobite:

Take some sharply focused photos without angles.  Top-down, lateral-side and a close-up of the cephalon, hopefully some more details will be revealed.

 

image.png.a84de26dad44fb03836a743755df237c.png

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10 minutes ago, piranha said:

Back to the mystery trilobite:

Take some sharply focused photos without angles.  Top-down, lateral-side and a close-up of the cephalon, hopefully some more details will be revealed.

 

 

 

DCS_0594~01.jpg

DCS_0596~01.jpg

DCS_0597~01.jpg

Website: https://www.instagram.com/paleo_archives/

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“It is by no means an irrational fancy that, in a future existence, we shall look upon what we think our present existence, as a dream.”

Edgar Allan Poe

 

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Thanks for the help Scott! 

 

Here's a later shot:

DCS_0600~01.jpg

Website: https://www.instagram.com/paleo_archives/

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“It is by no means an irrational fancy that, in a future existence, we shall look upon what we think our present existence, as a dream.”

Edgar Allan Poe

 

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The key feature on this trilobite is the prominent glabellar lobe.  After some color enhancement, I showed the photos to a colleague, and we agree the trilobite is an aulacopleurid.  There are a several species described from the Wenban Limestone in Adrain 2009, and Maurotarion periergum appears to be the best match.  As an added bonus, the paper also solves the mystery of Walcott's PhillipsiaBrachymetopus? riddle as: Mystrocephala sp. 

 

Adrain, J.M. (2009)
New and revised species of the aulacopleurid trilobite Maurotarion from the Lower Devonian (Pragian) of Nevada.
Zootaxa, 2215:1-23   PDF LINK

 

IMG.thumb.jpg.21b4ab4971756f84143f82274aa459e3.jpg

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2 minutes ago, piranha said:

The key feature on this trilobite is the prominent glabellar lobe.  After some color enhancement, I showed the photos to a colleague, and we agree the trilobite is an aulacopleurid.  There are a several species described from the Wenban Limestone in Adrain 2009, and Maurotarion periergum appears to be the best match.  As an added bonus, the paper also solves the mystery of Walcott's PhillipsiaBrachymetopus? riddle as: Mystrocephala sp. 

 

Adrain, J.M. (2009)
New and revised species of the aulacopleurid trilobite Maurotarion from the Lower Devonian (Pragian) of Nevada.
Zootaxa, 2215:1-23   PDF LINK

 

Your amazing! Thanks Scott :)

Website: https://www.instagram.com/paleo_archives/

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“It is by no means an irrational fancy that, in a future existence, we shall look upon what we think our present existence, as a dream.”

Edgar Allan Poe

 

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Scott,I downloaded that one just this morning,because of this thread:P

Zt is pretty good, graphically speaking.

 

 

 

 

 

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24 minutes ago, piranha said:

There are a several species described from the Wenban Limestone in Adrain 2009, and Maurotarion periergum appears to be the best match.  

 

I'm curious though, why M. periergum and not M. wenbanense? The axial spine seems much less wide on my specimen than on M. periergum, more in line with M. wenbanense. 

 

Screenshot_20170701-124804.png

Website: https://www.instagram.com/paleo_archives/

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“It is by no means an irrational fancy that, in a future existence, we shall look upon what we think our present existence, as a dream.”

Edgar Allan Poe

 

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22 minutes ago, MarcusFossils said:

I'm curious though, why M. periergum and not M. wenbanense? The axial spine seems much less wide on my specimen than on M. periergum, more in line with M. wenbanense. 

 

 

Just a slight amount of lateral compression would make the axial lobe appear to be narrower.

Also, Maurotarion wenbanense has prominent axial tubercles, Maurotarion periergum does not.

 

 

image.png.a84de26dad44fb03836a743755df237c.png

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Scott,i take it you mean some slight tectonic deformation has taken place?

 

 

 

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11 minutes ago, doushantuo said:

Scott,i take it you mean some slight tectonic deformation has taken place?

 

 

The paper does mention flattened, coarsely silicified trilobites, somewhat tectonically deformed.  However, it appears this specimen essentially preserves its original dimensions with a slight amount of lateral compression, probably by contemporaneous post-mortem compaction of sediment.  Because only the left peural lobe is slightly folded, tectonic deformation seems unlikely for the posted specimen.

 

image.png.a84de26dad44fb03836a743755df237c.png

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