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Malcolmt

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Interesting how something you read now can cause you to go back and have a look at something you put aside long ago because you did not think it was all that good or all that special. Last week Devonian Digger made a post "Trilobite in Need"  

This post got my interest because I did not realize any type of Dechenella was found at Penn Dixie. It got me to thinking that I should check out a box I had that contained what I believed to be a number of less than perfect greenops from Penn Dixie.  I had put these away over the years as only being worth prepping on a rainy day and after I am caught up. I am way too far behind in my prepping for myself and other people to even think about prepping what I know is not going to be complete or at least better than my current display piece of that species / locality.  My current best greenops is about 95% complete but a little distorted. A quick sort through them and this trilobite jumped out at me...... I had originally thought it was a damaged juvenile Greenops and was not likely going to be worth the effort that it would take to put it back together and then prep down from the top. You see the trilobite was split between two pieces of matrix and the front of the glabella was damaged and its genal spine was missing. I had found this at Penn Dixie in the summer of 2015.

 

Here it is as I had put it away two years ago

 

5951655d52c78_DechenellaPennDixiecroppedasfound.thumb.jpg.5894d36bebdeddd8884c89cb85982954.jpg

 

Note that I had originally trimmed the top piece in the field to reduce the carry back to the car weight. Those of you that know me realize that I take my saw pretty much everywhere. The good old boy scout in me "Always Be Prepared"

 

So this morning, I got out my dremel tool with a diamond cut off blade and trimmed the top half of the matrix down to a manageable size. When you do a top down prep you want to remove as much of the upper matrix as possible before gluing the parts back together. The more matrix you leave the longer it is going to take to get down to the trilobite again. It is actually quite worrisome when you take an exposed trilobite and cover it all back up in the hope that the end product will be better than what you started with.

 

Here is the trimmed piece of top matrix back in place. Seeing that the two parts had been separated for about two years they fit quite well. I used a thin non gap filling cyanoacrylate to do the bonding . Which I clamped for a few hours.

 

595166f61154e_DechenellaPennDixiecroppedBacktogether2.thumb.jpg.999d792e527e15626cbae1353df498b7.jpg

 

Note that I mark the boundaries of the bug with a black Sharpie. Usually I put an "H" or "T" to let me know the orientation but I could still see part of the bug so this was not necessary.

 

595166fc9169e_DechenellaPennDixiecroppedbacktogether.thumb.jpg.1dd4dc8b1d63aaa0b381f1df68ea1ada.jpg

 

Next comes the boring part of scribing down to the approximate area of the actual trilobite . This was accomplished with a CP 9361 until I got close and then a German Pferd MST 31 with a fine stylus to get closer.

The Pferd has a very fine stylus and a very high cycle rate (60,000). The scribing process took about 10 minutes

 

59516761985fa_DechenellaPennDixiecroppedtoptrimmeddown.thumb.jpg.11c044f6bf9c2fcb953b09cff9977b25.jpg

 

After about 30 minutes of air abrasion here is where we are in the process

 

 

 

 

5951694317cff_DechenellaPennDixiecroppednorestoration1.thumb.jpg.c6e2ac9a740b3f5589cfc9aed14c2fd3.jpg

 

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As you can see the air abrasion of the bug is now complete. COMCO unit using 15 PSI .015 nozzle and 40 micron dolomite under 20x magnification.

 

I am now at the point of deciding how much if any restoration I will do to this bug. It is cute and a species obviously that I did not have from Penn Dixie (or at least know that I had). It would probably benefit from some restoration 

 

So what is it. I am leaning towards it being a Pseudodechenella rowi. The dimensions of the bug are 

 

                                            14.7 mm long

                                             8.7 mm wide at pleura

                                             11.8 mm wide at tip of genal spines.

 

Not being familiar with other specimens I suspect that this is a juvenille as the other examples I have found are twice this size.

 

I am sure that Scott or Gerry will likely jump in to give me the correct identification. 

 

All in all not bad for something that until this morning was sitting in a shoebox wrapped in tin foil.

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The glabella and pygidium do not match with Pseudodechenella rowi.  Instead it looks more closely allied with another dechenellid: Basidechenella witherspooni.  Because that species is not previously reported from New York, it could possibly be an undescribed trilobite.  Hopefully GerryK can provide additional info.

 

IMG.thumb.jpg.f8a2062d8f89e72ba60d5065baa998b1.jpg

image.png.a84de26dad44fb03836a743755df237c.png

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Here they are under different light, matrix now matches real colour

 

Need to get my good camera back from my daughter!!!!!

 

5951877fb3f17_DechenellaPennDixiecroppedDifflight1.thumb.jpg.5348f4d023ff667983612c510eabe901.jpg

 

 

 

595187828e60b_DechenellaPennDixiecroppedDifflight2.thumb.jpg.8052e47492c7d28eb5d33af50de4cba8.jpg

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The lighting and angles of the earlier photos distorted the perspective.  

Looking at the new photos, it does appear to be Pseudodechenella rowi.

 

 

image.png.a84de26dad44fb03836a743755df237c.png

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Thanks Scott perhaps I will just label as Pseudodechenella sp but now you have me thinking it looks more like witherspooni. If I ever get my good NIkon SLR back I will try to take a picture on a photostand with a macro lens and a large F stop

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Try to take a perfect top-down photo.  The angled perspectives are distorting the glabella.

 

 

 

 

image.png.a84de26dad44fb03836a743755df237c.png

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I have seen Pseudodechenella rowi from Penn Dixie and believe your specimen is this species. Because your specimen is so small, it may not look like the larger specimens of Pseudodechenella rowi do to ontogenetic changes such as have larger genal spines. It's not a Pseudodechenella witherspooni because it has axial nodes and your specimen does not have them.

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Gerry,

 

Are all the Basidechenella now classified as Pseudodechenella?  Some are listed in your book with both names applied.

 

 

image.png.a84de26dad44fb03836a743755df237c.png

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Thanks Gerry, Definitely does not have axial nodes when I look at it under the scope

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Very cool! it is exciting to discover something awesome that one thought was really junk! That was the case with the first bone from Flexomornis howei that I found. I looked at it for 3 months in the field (thankfully, it was protected under some overhanging grass) before I got so sick of seeing it that I picked it up...

 

You could very easily have a new species in your possession waiting to be discovered!

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I dont know my trilo's from a hole in the ground, but I did enjoy your prep attack on this little critter. 

 

RB

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Great prep as usual, Malcolm. :) 

    Tim    VETERAN SHALE SPLITTER

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15 hours ago, piranha said:

Gerry,

 

Are all the Basidechenella now classified as Pseudodechenella?  Some are listed in your book with both names applied.

 

 

    All the Middle Devonian Basidechenella described by Stumm and Lieberman are now Pseudodechenella. The species "clara" in our book on page 154 was referred to Basidechenella by mistake and should have been referred to Pseudodechenella like it is on page 157. We referred the species "hessionea" to Basidechenella? because only a pygidium is known and could not determine if it is a Pseudodechenella without knowing what the cephalon looks like.

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On 6/27/2017 at 11:23 AM, GerryK said:

    All the Middle Devonian Basidechenella described by Stumm and Lieberman are now Pseudodechenella. The species "clara" in our book on page 154 was referred to Basidechenella by mistake and should have been referred to Pseudodechenella like it is on page 157. We referred the species "hessionea" to Basidechenella? because only a pygidium is known and could not determine if it is a Pseudodechenella without knowing what the cephalon looks like.

Gerry. does this hold true for even Devonian trilos up here n Ontario? I just wanted to clarify for finds at Arkona. :) 

...How to Philosophize with a Hammer

 

 

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Don't know how I missed this thread, but this is great! At first I wasn't 100% on P. rowi, only because I didn't see a margin on the pygidium, but in the other photos I can see it there. Definitely a nice piece. I'm very interested in the fact that these are starting to show up more and more from the site. Now if only we could start hauling out more Dipleura as well :P 

Jay A. Wollin

Lead Fossil Educator - Penn Dixie Fossil Park and Nature Reserve

Hamburg, New York, USA

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On 26.6.2017 at 10:04 PM, Malcolmt said:

  All in all not bad for something that until this morning was sitting in a shoebox wrapped in tin foil.

 

Well, how 'bout that! Good thing we've got a photographic memory when it comes to our fossils :)

 

Greetings from the Lake of Constance. Roger

http://www.steinkern.de/

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