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Mainefossils

Fossil forum, 

 

This is another fossil from the Leighton Fm haul. I was thinking coral, because of the external mold of it, but the internal mold has interesting segments. Unfortunately, the internal mold is missing a piece. Here are some pictures (internal mold on the left, external on the right): 

 

684248450_coral2.thumb.jpg.23d5ea735325d7fecc2d3c7b7e399be3.jpg     579687859_coral3.thumb.jpg.fd6a3ce78939e3b944da1c57fb174311.jpg

 

1631749673_coral1.thumb.jpg.15b8d83f854cfa8ace475fee3a13e8eb.jpg

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It is a (rugose) coral, and the lines you are seeing cross the septal grooves are growth lines. 

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Fossildude19

I would like to see more of it uncovered. 

As it stands now, to me, it looks like a Spyroceras orthocone cephalopod. 

I have one that looks similar to this. 


Here is one from the web: 

 

4657229826_f5c152e3ac_o-vert.jpg

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7 minutes ago, Fossildude19 said:

I would like to see more of it uncovered. 

As it stands now, to me, it looks like a Spyroceras orthocone cephalopod. 

I have one that looks similar to this. 

 

 

 

The bet is on! :D 

The problem with the Spyroceras ID is that they are to my knowledge restricted to the Devonian, and these Leighton Fm deposits are Silurian. Spyro's longitudinal grooves seem a bit more "regular" than in this piece. 

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FossilDAWG

I think it's a nautiloid.  The internal mold shows camerae and straight sutures,  The linear ornament on the external mold is found on lots of nautiloids, not just Spyroceras.  One example would be Kionoceras but there many others.  There is no trace of the "septal grooves" on the internal mold, but if it was a coral you would expect the septa to extend towards the interior.

 

Don

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I cede the point. Tim, I owe you a refreshing beverage. :D 

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Cornulites (cornulitid ?) 

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Mainefossils

Thanks for the info! I have found other nautiloids in this same formation, so this would make sense. Unfortunately, it seems that this is only a fragment, not the full shell, but I will make sure. Thanks again!

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Fossildude19
56 minutes ago, Kane said:

The bet is on! :D 

The problem with the Spyroceras ID is that they are to my knowledge restricted to the Devonian, and these Leighton Fm deposits are Silurian. Spyro's longitudinal grooves seem a bit more "regular" than in this piece. 

Kane, 

 

Like I said, I have one that looks very similar to the one Mainefossils posted, and more striations than the example I posted. 

It may not be Spyroceras sp. , but it does look quite similar, so maybe a related genus. 

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I still say show me septa, or it could be a cornulitid at that size. 

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FossilDAWG
18 hours ago, Rockwood said:

I still say show me septa, or it could be a cornulitid at that size. 

My interpretation of the fossil:

Maine nautiloid.jpg

 

Don

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IsaacTheFossilMan

The lack of septa on the internal mold make me think it isn't a coral, but a cephalopod instead. The shape makes me think Orthoceratoidea, not least because that slight curved shape is present in species of Orthoceratoidea. However, that shape could just be deformation, post-mortem.

 

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4 hours ago, FossilDAWG said:

My interpretation of the fossil:

 

Something tells me I won't win this one, but I need to find my Silurian examples before I throw in the towel. 

:headscratch:I think that box was deemed temperature stable. Probably in the garage.  :)

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FossilDAWG

Whenever we are working from photos everything has to be taken as a hypothesis and there is always room for interpretation. 

 

Don

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Now I have to concede. I just flat remembered wrong, and was too lazy to check, I guess. Conularids have a lapped appearance to the suture between their segments.  

I get a little squirrely this far into a Maine winter.

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Mainefossils

Thanks so much for the info! I will continue to look into your suggestions in available literature. Thanks again!

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