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ordovician hash plate help


dalmayshun

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On a recent trip I hunted the Jersey Road cut by the Harsha bridge over the Ohio river. I hoped to find edrioasteroids, but the site was way too large for me to even know where to begin. I did pick up a couple of hashplates I found interesting. I have collected several different Ordovician sites, and this one had all the usual types...brachiapods, bryozoans, crinoid pieces, and a few others. These needle like, triangular cross sectioned pieces were abundant. I hadn't seen them before, and couldn't i.d. them, so I brought back a hashplate of them knowing that someone on the forum would I.d. them for me. Thanks. Al;so, if someone could explain the biology of the crinoid stem piece, I would appreciate it as well. Usually I just find the "buttons" in the center, this one appears to have a disk around it, it looks rather thin, almost like flower petals around the outside edge, with a distinctive cell pattern inbetween. i tried to get the best , clearest photo I could with my camera. If you blow it up a bit, you'll see what I am talking about. I have included a side view to show its thin edge.  The crinoid stem is about 1/2 " across. Center button is perhaps 3/16" or so. Thanks. And i have included another interesting crinoid section, simply because it is a form I haven't seen before...the circle, with little bead like bumps in the underlying area. Forgot to add, I was curious about the little ball with bumps all over it...It was by itself in the top of a hashplate, and popped out when I cracked the plate apart. I don't recognize it either. 

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On 7/29/2018 at 11:01 AM, dalmayshun said:

don't recognize it either. 

20180729_102118-picsay.jpg

I think these are trace fossil burrows.  @abyssunder is really good at these and might be able to put a name on them.

 

On 7/29/2018 at 11:01 AM, dalmayshun said:

 

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I think this one might be a little bryozoan colony.  I can't see if it has tiny pore-like zooecia.  If it does, then the bumps are monticules.  Do you see little pores with a hand lens?

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I have never seen a plate like this in the Ordovician, very cool. Looks like a collection of echinoderm spines but wrong age. I think they are trace fossils. The scars are where the little round bryozoans (looks like Prasopora sp.}  were attached

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Thank you for the kind words, Pete! :)

 

Somehow, the elements visible on the surface, reminds me of trace fossils (e.g. Lockeia isp.), but the strange features like crosses ("cruciform penetration twinning") lead me to think they are geological features, minerals like Staurolite or similar.

 

Crinoid columnals (like the ones from the forth picture of OP) are column parts.

 

columnal-description.jpg.72398637c92afb0aeffe235ccce8b10c.jpg

 

I'm not sure what represents the second picture (OP). If crinoid element, it might be close to a brachial.

2.thumb.jpg.8aca8cb9fb0ecab6fd10bed08cbe3b40.jpg

 

The last picture (OP) has not enough details for a more correct ID, but the specimen in it reminds me of a cystoid theca. I could be wrong, also.

 

 

 

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