Cyclosystoid or something else? Central PA (USA) Silurian

[SteveE]

Found this piece of float in a place where there is a mix of native scree and fill from God knows where.    Due to circumstances I was not able to climb the slope to try to find a source layer.   Exposed bedrock I think is Mifflintown Formation.   The slab of hash shows three reasonably clear specimens without any prep.   Each has a ring with triangle segments pointing toward the center, and one pair of dominant rays running from the center to the perimeter.   Someone on the FB group pabe suggested "Cyclosystoid" which I had never heard of, and there is only a little available on google that isn't paywalled.   Eventually I'll focus on the other species in the hash to try to verify its Mifflintown and not trucked in fill from who knows where.   What do you thiink?   (PS  thanks for the lead so far, Greg)

 

[sTamprockcoin]

I'd lean more toward crinoid section but I'm wrong more often than not.we'll se what others have to say.

[Jeffrey P]

I agree with crinoid stem sections.

[DeepTimeIsotopes]

It certainly looks similar to @Malcolmt‘s in this thread but without the radial spokes yours has

 

[DeepTimeIsotopes]

Take a look at this sketch of this species

http://www-personal.umich.edu/~wstoddar/cyclocystoid.html

 

If yours are cyclocystoids, then they appear slightly worn. Maybe others can jump in with their expertise. 

[SteveE]

None of the specimens have a space for a lumen (in filled or not).  instead,  the rays rise slightlyright in the center coming together in a small mound. )See pics 2 and 3).    I also thought they were a weird crinoid when I collected it, but have struck out looking for samples of crinoids  with rays and a ring of inward pointing traingular segments.   Then when I read this, Greg's ID on the FB page sounded better and better....

 

FYI  snippet from

M.A.P.S Digest V 15 No 4 1993 (Mid America Paleontology Society)

 

Cyclocystoids are characterized by a flattened aboral disc that was attached to the sea floor. The disc was composed of weakly calcified plates in a tough leathery tegmen that may have resembled a sea cucmber/s. The oral disc faced upward with a mouth located centrally on the summit. Numerous food grooves radiated outwards from the mouth in all directions towards the submarginal ring.

 

https://ir.uiowa.edu/cgi/viewcontent.cgi?referer=https://www.google.com/&httpsredir=1&article=1131&context=midamericapaleo

[Al Dente]

They might be casts of solitary “button” corals.

 

 

[Jackson g]

2 hours ago, Al Dente said:

They might be casts of solitary “button” corals.

 

 

+1

[SteveE]

Thanks for the help thinking about this.  I hope I don't come across as arguing.   I suppose you might say I'm an advanced beginner and there's a lot I've never heard of so please keep it up!   Can anyone narrow the candidates down if its a crinoid or button coral?  All the horn corals I've seen or looked at online seem to have a depressed center in the oval where the creatures mouth should be.   I set a light for an oblique shot (like moon mountains at sunrise).   This shows the center of the disk as a small mountain, rather than a basin.   The tick marks on the near side of the rule are 1/64".     

 

FYI, the image with the earlier suggestions of button coral is from this paper https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0136289

 

[Malcolmt]

I have been fortunate to find quite a few cyclocystoids since that first one I found and this does not look to me to be one. I would probably lean towards a button coral. I am unfamiliar with the formation you collected in but I would look to what is found there. Has there ever been a cyclo found. If I see a four legged animal with a mane and tail running very quickly in Arizona I think Horse. If it was Africa then Zebra........

[SteveE]

thanks for the help, all.   I'll call it casts of button coral for now (leading contender genus Palaeocyclus).  Hopefully if I can gain access to the slope to try to find the source layer.

[sTamprockcoin]

I can't find any  geologic lit refs to cyclostoids in the bloomsburg/mifflintown formation. I think the button coral is likely. I've collected from the same site and even most of the fill seems local - most from construction & reconstruction of the ovelooking & nearby highway. That slope is best collected in winter before plants grow and store employees are outside smoking!

[TqB]

Lovely little things! I'm sure they're solitary corals - not casts/moulds though, they seem to be the actual weathered out skeletons. The raised columella in the centre is normal for many types - it isn't Palaeocyclus which has no axial structure and more regular septa.

It's closer to some Microcyclus, as @Al Dente suggested, and the calicular surface of these is usually domed up. That's Devonian by the way - there's plenty of Devonian in central Pennsylvania so would that be possible?

[SteveE]

1 hour ago, TqB said:

Lovely little things! I'm sure they're solitary corals - not casts/moulds though, they seem to be the actual weathered out skeletons. The raised columella in the centre is normal for many types - it isn't Palaeocyclus which has no axial structure and more regular septa.

It's closer to some Microcyclus, as @Al Dente suggested, and the calicular surface of these is usually domed up. That's Devonian by the way - there's plenty of Devonian in central Pennsylvania so would that be possible?

Thanks...  I've temporarily lost access to paywalled journal articles and look forward to following up on those comments when I get it back.   Yes, the road construction might have trucked in Devonian fill so that's certainly possible.