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Composite orthiconic nautiloid


BobWill

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I know some of you find very complete nautiloids that are much larger but here in Texas they are often smaller and fragmentary, though the pieces can be well preserved and easy to extract from the loose shale of the Graham Formation at Jacksboro Texas. I had many fragments separated into boxes labeled "Pseudorthoceras" and "Mooreoceras" for smaller and larger segments respectively. Then I saw a paper that invalidated the latter genus, Revision of Some Common Carboniferous Genera of North American Orthocerid Nautiloids, Kröger & Mapes 2005, which made all of my specimens Pseudorthoceras knoxenses.

 

This got me wondering what these creatures might have looked like whole so I started to gather a few fragments that might fit together in a continuous shell, including a piece with the protoconch and one with part of the body chamber. The result had one empty space which I filled with a clay reconstruction, then made a plaster mold from which I poured a plaster cast to fill the gap. I used super glue to hold everything together so I could take it apart with acetone if I wanted too. It may make a good display fossil for our table at local events though so I'll probably donate it to the Dallas Paleontological Society.

 

The second section from the large end is the fake part. The rest are all genuine fossils from the same site but collected over several years, so not even considered to be associated. I'm pretty sure they are all the same species though. The whole thing is 38cm long and came out fairly straight considering what I had to work with..

 

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IMG_20200805_225514808.thumb.jpg.45692ac4b31e9363f2606b13ae5b51bf.jpg

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6 hours ago, RuMert said:

Looks cool, maybe the decline in thickness is a bit too sharp and a couple of additional sections would add to the overall impression

Good point. I was concerned about being off in either direction with so little to go by. I suppose I could establish a ratio from the longest section but I still only have a few dozen pieces to choose from and don't want to break any specimens to make them right. It would be great if anyone has a really long piece intact or enough associated pieces to get a better idea of the apical angle. I'll have a closer look at the paper I mentioned to see if the answer is there.

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  • Fossildude19 changed the title to Composite orthiconic nautiloid

Nice composite example, Bob!  :) 

    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."

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Looks good Bob! Much better than I could do, I am sure. I agree that it would make a great fossil example to show visitors that stop by the D.P.S. exhibition table! 

The good thing about science is that it's true whether or not you believe in it.  -Neil deGrasse Tyson

 

Everyone you will ever meet knows something you don't. -Bill Nye (The Science Guy)

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Good eye @RuMert. Measuring the longest piece gave me a ratio of tapering (or whatever you would call the change in diameter per unit of length) of .1224 : 1. This made the overall length short by 16mm. Still not bad.

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