Eurypterid or sponge bored orthocone? Revisiting a Mississippian puzzle

[TqB]

A while ago, I was convinced that this was an orthocone with possible sponge borings though it was never really resolved.

http://www.thefossilforum.com/index.php?/topic/77979-strange-infestation-on-orthocone-shell-mississipian-ne-england/&

 

@Al Dente suggested eurypterid as a possibility which I argued against, largely because they've never been found around here. However, a friend of mine has now found some undoubted eurypterid fragments in equivalent beds in Scotland, 120 miles away or so and where the faunas have much in common. He's pretty sure that this is indeed eurypterid (based on just a couple of closeup photos). I'm rather hoping it is though the boring sponge is also pretty interesting.

 

Searching throws up Adelophthalmus as a distinct possibility, based on the ornament (see reference and drawing at the bottom of the post).

 

So here it is again - eurypterid or bored orthocone? Brigantian (Mississippian) marine shale, Co. Durham, NE England.

(Many more photos on the original thread, including very close up. The little rings are preserved in solid pyrite and go right through the shell/carapace.)

 

 

From this paper on Pennsylvanian Adelophthalmus

https://www.foss-rec.net/8/3/2005/fr-8-3-2005.pdf

 

[Al Tahan]

Ok since you put Eurypterid in the title I have to weigh in!!! Lol. 

 

I do have to lean towards orthocone. Ornamentation on Eurypterids are not round....at least none that I’ve seen first hand or in publication. I’ve seen a lot of Eurypterid parts with it from hands on experience so I’m decently familiar with what to look for. The Eurypterid in the picture you referenced shows non circular ornamentation. 

 

It also seems far too straight and non tapered to be a Eurypterid. I’m adding a photo with some marks I made on your photo to show the defivintive margins of the fossil. It just seems too straight and too wide for too long without tapering. 

 

Just my thoughts. I’m kinda a Eurypterid nut so I love these topics! 

 

Al 

[TqB]

2 minutes ago, Al Tahan said:

Ok since you put Eurypterid in the title I have to weigh in!!! Lol. 

 

I do have to lean towards orthocone. Ornamentation on Eurypterids are not round....at least none that I’ve seen first hand or in publication. I’ve seen a lot of Eurypterid parts with it from hands on experience so I’m decently familiar with what to look for. The Eurypterid in the picture you referenced shows non circular ornamentation. 

 

It also seems far too straight and non tapered to be a Eurypterid. I’m adding a photo with some marks I made on your photo to show the defivintive margins of the fossil. It just seems too straight and too wide for too long without tapering. 

 

Just my thoughts. I’m kinda a Eurypterid nut so I love these topics! 

 

Al 

 

Many thanks, Al, very useful, I was hoping people familiar with eurypterids would weigh in.  

Re circular ornament, I found this Ordovician one:

https://bmcevolbiol.biomedcentral.com/articles/10.1186/s12862-015-0443-9

 

[Al Tahan]

9 minutes ago, TqB said:

Many thanks, Al, very useful, I was hoping people familiar with eurypterids would weigh in.  

Re circular ornament, I found this Ordovician one:

https://bmcevolbiol.biomedcentral.com/articles/10.1186/s12862-015-0443-9

 

Ok nice! So circular ornamentation are a thing just not on the Silurian critters. I’m still leaning towards orthocone at the moment but now only based on shape. I can’t use ornamentation as a clue anymore lol. I’m still leaning orthocone but I do have more questions now that you showed me that Ordovician Eurypterid link. What did the other Scottish Eurypterid look like that your friend found? You may be able to draw some connections if there are some. Maybe the other Scottish Eurypterid has some ornamentation? Post a pic of on the thread so we can compare!  

 

Hope this is helping 

 

Al

[TqB]

36 minutes ago, Al Tahan said:

Ok nice! So circular ornamentation are a thing just not on the Silurian critters. I’m still leaning towards orthocone at the moment but now only based on shape. I can’t use ornamentation as a clue anymore lol. I’m still leaning orthocone but I do have more questions now that you showed me that Ordovician Eurypterid link. What did the other Scottish Eurypterid look like that your friend found? You may be able to draw some connections if there are some. Maybe the other Scottish Eurypterid has some ornamentation? Post a pic of on the thread so we can compare!  

 

Hope this is helping 

 

Al

Thanks again, yes, please keep the comments coming! I haven't seen his specimens yet (validated by a specialist I think) but he says they're totally smooth.  

I'm guessing that Carboniferous ones may be different again from many earlier Palaeozoic ones as most of them became extinct in the Devonian - I've read that the adelphthalmids are the most common.

[RCFossils]

Neat Piece!

I am also in the orthocone camp.

The circular structures do not look like any type of carapace ornamentation that I have seen.

Some of the circular structures appear to be sitting between where the tergites come together.

[Al Tahan]

I’m really interested to see this specimen! See if he will send you a picture to share . It would really help with your fossil! 

[Al Tahan]

8 minutes ago, RCFossils said:

Neat Piece!

I am also in the orthocone camp.

The circular structures do not look like any type of carapace ornamentation that I have seen.

Some of the circular structures appear to be sitting between where the tergites come together.

Nice attention to detail!!  I didn’t notice that first time around..... I’m really sure those are not ornamentation now. Seems “overprinted” on the fossil. As mentioned above, probably a boaring sponge (not the best with sponges lol)? 

 

That confirmed Scotland Eurypterid will be a good tell about this fossil. I’m still team orthocone for now lol......but now I’m just curious as heck about this confirmed Eurypterid from Scotland ha. 

[TqB]

2 hours ago, RCFossils said:

 

I am also in the orthocone camp.

The circular structures do not look like any type of carapace ornamentation that I have seen.

Some of the circular structures appear to be sitting between where the tergites come together.

I believe you're right, and there are patches of thin shell showing that pass right over the joins which must be cephalopod septa after all.

 

OK, back to weird sponge borings! Thanks, guys.

[TqB]

4 hours ago, Al Tahan said:

Nice attention to detail!!  I didn’t notice that first time around..... I’m really sure those are not ornamentation now. Seems “overprinted” on the fossil. As mentioned above, probably a boaring sponge (not the best with sponges lol)? 

 

That confirmed Scotland Eurypterid will be a good tell about this fossil. I’m still team orthocone for now lol......but now I’m just curious as heck about this confirmed Eurypterid from Scotland ha. 

It's in storage at the moment, he moved house - says he'll get it out soon though and I'll add it here.  

[abyssunder]

I'll remain in my Entobia thought.

 

BTW, Camera lucida is not a species name, it's an instrument, so I can't imagine why it was  italicized in the document above.

[TqB]

59 minutes ago, abyssunder said:

I'll remain in my Entobia thought.

 

BTW, Camera lucida is not a species name, it's an instrument, so I can't imagine why it was  italicized in the document above.

Thanks, I'm fully back to that thought  too.

 

Re the italics - it's normal to italicise Latin and other languages if the words aren't in common use, in English anyway. "Camera lucida" may be unusual enough to merit this?