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So far I have posted many members of the family Acastidae.  All have been from the early or middle Devonian, which was the heyday of the Acastidae, although some trilobites in that family did live into the Frasnian.  But like other Devonian trilobite families this family had its origins prior to the Devonian.  Here, with trilobite #171, I show my only Silurian member of the Acastidae -- Acastocephala macrops of Middle Silurian age from the Wenlock Series of the Coalbrookdale Formation at Coalbrookdale, Shropshire, England.  It's a rather plain trilobite that doubtless had no conception of the fantastic forms that descendants of its family would take on.

 

In the background of the middle picture is the partial pygidium of a Dalmanitid trilobite.  Unfortunately the rest of that trilobite is not present.

dorsal-rotated-small.jpg

left-cropped-small.jpg

left-eye-cleaned-small.jpg

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ClearLake

Another interesting one.  Every now and then I just like to scroll back through this thread to see the wonderful array of trilobites.  I hope your collection still has many more to go!

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piranha
21 hours ago, rew said:

Acastocephala macrops of Middle Silurian age from the Wenlock Series of the Coalbrookdale Formation at Coalbrookdale, Shropshire, England.

dorsal-rotated-small.jpg  left-cropped-small.jpg  left-eye-cleaned-small.jpg

 

 

Acastocephala macrops has many more eye lenses than this one.  Instead this specimen matches better with another Coalbrookdale acastid trilobite: Acastoides constricta.  Although A. constricta  also has more eye lenses, according to Shergold 1966, this species has a close relationship to Acastoides henni henni  Richter & Richter 1952, differentiated by a greater number of lenses; a maximum of up to 7 lenses in any lens file compared with 4 per lens file in A. henni henni.

 

Pending any possible future description you could give it a tentative label: Acastoides sp. (aff. A. henni henni Richter & Richter 1952)

 

image.thumb.png.28bc69b2daf3892a91e931e2bdf488b6.png

 

Richter, R., Richter, E. 1952

Phacopacea von der Grenze Emsium/Eiflium (Tril.).

[Phacopacea from the Emsian/Eiflian Boundary (Tril.).]

Senckenbergiana Lethaea, 33:79-107

 

Shergold, J.H. 1966

A Revision of Acaste downingiae (Murchison) and Related Trilobites.

Palaeontology, 9(2):183-207  PDF LINK

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Posted (edited)

Note to self:  Don't even bother to label a trilobite until I post it here and Piranha tells me what I got wrong.  The eyes do look like a close match for Acastoides henni henni.

Edited by rew
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piranha

The low lens count eyes are also similar to various other species of Acastoides.  Because A. henni henni is Devonian, this appears to be an undescribed species.

 

Here is another similar example from the "Acastoides henni-Gruppe" of the Devonian of Germany:

 

image.png.ccb4f41be3cfe5290c0adad623b2c59c.png

Basse, M., Müller, P. 2016

Trilobiten aus dem Ober-Emsium und Frühen Eifelium der Südlichen Lahnmulde (Rupbach-Schiefer, Leun-Schiefer und Ballersbach-Kalk).

[Trilobites from the Upper Emsian and the Early Eifelian of the Southern Lahn Syncline (Rupbach Shale, Leun Shale, and Ballersbach Limestone).]

Abhandlungen der Senckenberg Gesellschaft für Naturforschung, 572:1-329

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Posted (edited)
15 hours ago, ClearLake said:

Another interesting one.  Every now and then I just like to scroll back through this thread to see the wonderful array of trilobites.  I hope your collection still has many more to go!

I'm glad you like it.  There's still many trilobites to photograph.  And still more misidentifications that need to be clarified by Piranha.

Edited by rew
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Trilobite of the week #172 is Dalejeproetus sagaouii of Early Devonian (Pragian) age from the Lhandar Formation at Mrakib, Ma'der, Morocco.  This was an inexpensive proetid that I bought just to round out  the collection.  Being bent over, it was a bother to photograph (it's always easier to photograph the prone trilobites), and I considered the preparation to be acceptable but nothing special.  So I was pleasantly surprised to see that the lenses of the holochroal eyes are mostly preserved.  In fact, these are the best preserved eyes I've ever seen on a proetid.

 

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rear-cropped-small.jpg

left-eye-cleaned-small.jpg

right-eye-cleaned-small.jpg

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Sjfriend

More great bugs!

 

Thinking about all of @piranha's "corrections" it's too bad back at the beginninwe of this thread we didn't start a betting pool (to raise funds for all your new labels :default_rofl:) of just how many he would change

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Trilobite of the week #173 is Tamdaspis gingxiensis of Late Cambrian age from the Sandu Formation at Guole, Guangxi Province, China.  This is the only trilobite I have in the family Ceratopygidae within the superfamily Asaphoidea.  This is another modest priced bug I got to expand the diversity of my collection.

 

 

dorsal-cropped-rotated-small.jpg

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