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Unknown Trilobite... Radnoria?


Fossildude19

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I've had this on my shelf for a number of years now, and have finally decided to ask for an ID.

It was found in a river cobble in Herkimer NY, along the river that runs alongside Rte. 28.

The area is mostly Ordovician, but,... like I said, this was found in float from a river bed.

Unfortunately there is damage to the cephalon - which complicates matters. :unsure:

I was thinking Radnoria,...but would like some other opinions. The specimen is roughly 8mm long by 6.5 mm wide.

Thanks in advance for any help.

Regards,

post-2806-0-83411400-1307186817_thumb.jp post-2806-0-14606000-1307186828_thumb.jp

    Tim    -  VETERAN SHALE SPLITTER

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Really difficult item Tim, seeing as the size suggests it is a meraspid.

I count 6 thoracic segments on your specimen, and this would acknowledge my suspicion as pretty much all adult proetids I know from your state have at least 9.

It could also very well be a meraspid of one of the following Ordovician genera: Bathyurus, Raymondites, or a Devonian Dechenella?

The crystalline matrix it is in may be able to help you get closer to solve this mystery?

I don't think that it is typical for the Silurian in your area, or is it?

Good luck!

cheers,

Mark

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Really difficult item Tim, seeing as the size suggests it is a meraspid.

I count 6 thoracic segments on your specimen, and this would acknowledge my suspicion as pretty much all adult proetids I know from your state have at least 9.

It could also very well be a meraspid of one of the following Ordovician genera: Bathyurus, Raymondites, or a Devonian Dechenella?

The crystalline matrix it is in may be able to help you get closer to solve this mystery?

I don't think that it is typical for the Silurian in your area, or is it?

Good luck!

cheers,

Mark

Mark,

Thanks for your reply. :)

I'm not real familiar with the rocks of that area - the matrix around this piece is a very hard/chert - like type of rock.

Most of the rock in the area is a typical Ordovician black shale.

I will check the other species you mention.

Thanks again!

Regards,

    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  

__________________________________________________
"In every walk with nature one receives far more than he seeks."

John Muir ~ ~ ~ ~   ><))))( *>  About Me      

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More pics.

post-2806-0-95863800-1307191991_thumb.jp post-2806-0-96252400-1307192036_thumb.jp

post-2806-0-82966500-1307194619_thumb.jp post-2806-0-74917200-1307194998_thumb.jp

    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  

__________________________________________________
"In every walk with nature one receives far more than he seeks."

John Muir ~ ~ ~ ~   ><))))( *>  About Me      

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Hmm, upon closer inspection: The amount of axial rings on the pygidium actually rules out any Bathyuroidea.

The smooth exoskeleton rules out Radnoria.

I think I would stick to a representative of the genus Dechenella, which would make it Devonian.

I must add that the preservation looks so exceptional you may want to spend time tracking down the parent strata.

cheers,

Mark

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Mark.

Unfortunately, this was found over 10 years ago, and the site is about 3-4 hour drive from my home. :unsure:

I may have to check the area again, sometime in the future. :)

I appreciate your efforts.

Thanks again.

Regards,

    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  

__________________________________________________
"In every walk with nature one receives far more than he seeks."

John Muir ~ ~ ~ ~   ><))))( *>  About Me      

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I'm gonna throw my hat into the ring of ideas and say I believe it may be a juvenile Isotelus. The hypostome is visible where the glabella is missing and it's looking very Isotelus-ish. Here is a growth series of Isotelus gigas based on Raymond, 1941.

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Caleb is correct as this is certainly an isoteline trilobite. This individual exhibits six segments as a meraspid that had not yet fully released all of its thoracic tergites yet. For comparison one would expect a size of approximately 3mm for an isotelid meraspid with only one segment released (M1). Figured drawings appear to suggest a more defined 3D pygidial axis in I.gigas that would have become lost by the holaspid stage of development. If the lower Ordovician of New York is a possibility then Isoteloides canalis has a distinctive pygidial axis that warrants consideration as well.

post-4301-0-02261300-1307202808_thumb.jpg post-4301-0-61007400-1307202816_thumb.jpg

image.png.a84de26dad44fb03836a743755df237c.png

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I'm gonna throw my hat into the ring of ideas and say I believe it may be a juvenile Isotelus. The hypostome is visible where the glabella is missing and it's looking very Isotelus-ish. Here is a growth series of Isotelus gigas based on Raymond, 1941.

Caleb,

Wow - I never would have thought of that!!!

Thanks for your insights!

That 1st picture in the series certainly looks very close! :)

Thanks so much for your answer!

Regards,

    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  

__________________________________________________
"In every walk with nature one receives far more than he seeks."

John Muir ~ ~ ~ ~   ><))))( *>  About Me      

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Caleb is correct as this is certainly an isoteline trilobite. This individual exhibits six segments as a meraspid that had not yet fully released all of its thoracic tergites yet. For comparison one would expect a size of approximately 3mm for an isotelid meraspid with only one segment released (M1). Figured drawings appear to suggest a more defined 3D pygidial axis in I.gigas that would have become lost by the holaspid stage of development. If the lower Ordovician of New York is a possibility then Isoteloides canalis has a distinctive pygidial axis that warrants consideration as well.

post-4301-0-02261300-1307202808_thumb.jp post-4301-0-61007400-1307202816_thumb.jp

Scott,

Thanks for your efforts. I appreciate all the info. :)

I'm a total amateur when it comes to Trilobites.

I have a bit of home work to do, it would seem.

Thanks again - it's very appreciated!

Regards,

    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  

__________________________________________________
"In every walk with nature one receives far more than he seeks."

John Muir ~ ~ ~ ~   ><))))( *>  About Me      

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