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Georgia Fossil - Dome shaped


darrenrx

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Hi Fossil Forum,

I need help in identifying several fossils my friend found in middle Georgia. The area where he found them has been reported to have fossils from the Ordovician Period. They were found in a soft limestone sedimentary rock. The fossils may be in the sand dollar family, but don't appear to have a star shape on top. The dome is somewhat elongated and appears to have fine fibers running from the top of the dome to the bottom edge.

Any idea what he found?

Thanks,

Darren

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Here is a high definition picture of one of the fossils. It shows clear striation lines. I hope this helps confirm identification of the fossil.

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I think a closer look at the dome shape may help. These striations appear to be a piece of shell that was engulfed by an encrusting organism. It looks like there is an ichno fossil within it.

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The first set of pictures id definitely Bryozoan. I found one that looks just like it this summer in some Ordovician Limestone in Ontario back in August.

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The rocks I wander through are Ordovician. When something like your find is discovered locally, people call it Prosopora bryozoan. Just a guess from a novice with a little knowledge.

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looks like some kind of sponge to me. I am not getting a bryozoan vibe even though Homotrypella has that general shape, no pores that I can see.

"Absence of evidence is not evidence of absence"_ Carl Sagen

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This fossil, like the others darrenrx has posted in other threads, is Eocene. I suspect he was mislead by this web site, which contains erroneous information. There is no Ordovician in Middle Georgia, the bedrock is mostly Eocene with a smattering of Oligocene.

The fossil in question is a bit hard to determine from the photos, but the dome shape and striations suggests a mold of a bryozoan colony such as Lunulites. Relatively large colonies of this bryozoan do occur in the Eocene limestone in the area.

Don

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can't see a resemblance to Lunulites, at least to the ones I have they are small button shapped discs.

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"Absence of evidence is not evidence of absence"_ Carl Sagen

No trees were killed in this posting......however, many innocent electrons were diverted from where they originally intended to go.

" I think, therefore I collect fossils." _ Me

"When you have eliminated the impossible, whatever remains, however improbable, must be the truth."__S. Holmes

"can't we all just get along?" Jack Nicholson from Mars Attacks

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  • 2 weeks later...

My friend went back to Houston county and found some better examples. He has identified the layer as Tivola limestone from the Eocene period. I hope this helps with identification.

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It is one of the domed bryozoans as several people have already stated. Lunulites is a good fit, particularly since these are molds and not whole fossils. Lunulites are odd among the bryozoa in that they have aragonite in their skeleton. Aragonite is less stable than calcite.

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Here are some exemples from Europe:

Lunulites urceolata,Eocene,France_13mm post-17588-0-77153800-1449490277_thumb.jpg

Lunulites conica,Neogene,Great Britain post-17588-0-04364700-1449490293_thumb.jpg

Lunulites hagenowi,Maastrichtian post-17588-0-60374600-1449490308_thumb.jpg

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