Unknown Mississippian, barley twist rod.

[TqB]

Does anyone recognise this? It's in a piece of Mississippian Great Limestone (north east England) that I'm acid dissolving for silica replaced fossils. 

It's about 7mm long and I'm stumped. I don't think it's bryozoan - no sign of branches or zooecia and we don't have Archimedes  which it vaguely resembles. Foraminiferan? It has a resemblance to strings of Saccaminopsis (calcareous alga spheres) that also occur but they don't have the twist.

 

Scale in mm

 

 

 

In context, with brachiopods, brachiopod spines, corals, gastropods

 

 

Edited April 28 by TqB

[TqB]

This is opposite sides of a fragment that appears to be the same.
About 3mm long.
 

 

I was considering a bryozoan after all, Diploporaria, but it doesn't convince me:

[Bullsnake]

I cant be much help, Tarquin, but if not a foram or bryozoan, could it possibly be sponge?

Is a cross section of an end possible?

[Rockwood]

I think graptolites twist. Could it be? 

[TqB]

56 minutes ago, Bullsnake said:

I cant be much help, Tarquin, but if not a foram or bryozoan, could it possibly be sponge?

Is a cross section of an end possible?

Thanks, Steve, I hadn't thought of that but there's no indication that it is. It's less than 1mm thick so this is the best I can do with my camera; it seems to show just the sugary silica particles that have replaced calcite. It looks solid but I can't rule out that it was originally tubular.

[TqB]

On 4/28/2024 at 7:09 PM, Rockwood said:

I think graptolites twist. Could it be? 

Thank you; it would have to be a dendroid in the Carboniferous and there's no record at all of them in UK Carboniferous limestones, only shales and not around here.

(It reminded me of one too!)

Edited May 2 by TqB

[TqB]

Another specimen (I have three now), thinner, curved and apparently tapering to an origin.
It also appears to be hollow/tubular.

 

6mm long, mm scale. (The background is smooth white card.  )

 

[TqB]

The original has now come free of the matrix and I can confirm that it's genuinely spiral. It also appears to be hollow.

A weird gastropod maybe??

Three sides:
 

[Bullsnake]

Worm tube?

This is the closest 'spirally' one I could find with a quick search.

https://www.researchgate.net/figure/Treptichnid-subhorizontal-burrow-systems-from-the-Cambrian-A-Treptichnus-pedum-from-the_fig2_230844985

[Rockwood]

36 minutes ago, Bullsnake said:

Worm tube?

I had considered that, but I've never seen a worm with that degree of focus. 

[TqB]

On 4/29/2024 at 8:51 PM, Bullsnake said:

Worm tube?

This is the closest 'spirally' one I could find with a quick search.

https://www.researchgate.net/figure/Treptichnid-subhorizontal-burrow-systems-from-the-Cambrian-A-Treptichnus-pedum-from-the_fig2_230844985

Thank you for looking! I'm sure it's not a trace fossil but an originally calcite tube. There weren't any definite tube secreting worms until the Triassic 
but it could well be one of the lookalikes.

 

There's an excellent summary here - with a section on possible Palaeozoic ones starting on p. 138 though none are figured.
Written in stone: history of serpulid polychaetes through time

 

 

 

Edited May 2 by TqB

[TqB]

This split specimen just turned up in a fresh sample from the same block and shows a continuous hollow down the centre. (Very sugary silica preservation.)