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Any Idea Fossil Id Needed


FossilsAreAwesome

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It is a fossil fern leaf. I am assuming you mean St Clair PA? If that is correct then it is Pennsylvanian era (200 - 303 m.y.o) I am sure there are those who can pen down the species.

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njfossilhunter

Welcome to the forum....very nice fern. I have collected at this site a few times ...it was always a good day hunting the pennsylvanian.

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Fossildude19

Hi Cathy,

This one is a bit tricky.

I took the liberty of fiddling with the contrast on your image.

post-2806-0-49019100-1429149449_thumb.jp

I'm not sure with this specimen. It could be a Neuropteris sp., but I cannot make out the veining in the pinnules, or if the pinnules are attached to the stem directly, or by stem of their own.

If the stem is mostly missing as an artifact of preservation, it could also be Pecopteris sp. I am also leaning towards Pecopteris because it appears (to me, at least ) that the mid-vein runs directly to the top of the pinnule, not halfway like in Neuropteris.

Here is a website that shows how to tell the two apart. Unfortunately, the preservation on yours is such that making a determination is a bit tricky.

But Pecopteris has my vote.

Hopefully one of the plant experts (Paleoflor) will weigh in.

Regards,

PS - cool find! :)

Edited by Fossildude19
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I noticed something interesting with your fiddling with the contrast. The fern appears to be preserved in pyrite. Very nice. Photo (from the Fossil Forum) is a pyrite fossil from St Clair PA

post-17624-0-81507400-1429151966_thumb.jpg

Edited by BigGuy
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Fossildude19

I noticed something interesting with your fiddling with the contrast. The fern appears to be preserved in pyrite. Very nice. Photo (from the Fossil Forum) is a pyrite fossil from St Clair PA

Slight correction - I found a good explanation of the colors at this website, which states:

"The seed fern fossils shown here represent plants in an ancient bog over 300 million years ago--long before dinosaurs roamed the earth. They are the type of plants that compressed into coal over time. The site from which these fossils were collected is the only area in the world where the fossils show dramatic white to yellow-orange colors, as opposed to brown or black compressions at other sites. The colors are entirely natural--the result of a unique preservational environment. The plants lived in a swampy, oxygen poor habitat. When they died, a combination of low temperature, pressure, and oxygen allowed the plant tissues to be replaced by pyrite (iron sulphides). Pyrophyllite (aluminum silicate, a whitish mineral) is believed to have replaced the pyrite later, as the sediments piled up and the temperature and pressure increased. The yellow and orange colors are caused by iron oxide residues. Several different plant species are found at the site; the most common are seed ferns called Alethopteris, Neuropteris, Pecopteris, and Sphenophyllum, with Alethopteris by far the most common."

So, technically, while they were replaced by pyrite at one point sometime in the distant past, the pyrite has since become pyrophyllite, which causes the white powdery look to the fern fossils. The oranges and yellows are actually iron oxide residues.

The website does make a mistake in saying it is the only site in the world that has this preservation. There is another in Rhode Island, and one in Massachusetts, and I believe there was a site in Germany with similar preservation as well. The last two I believe are now closed to collecting.

Regards,

Edited by Fossildude19
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If it is Neuropteris it is a seed fern (which is not the same as a true fern - not closely related). If it is Pecopteris it would be a true fern.

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The pinnules are restricted at the base which if this separated the lamina from the rachis then you would have a Neuropteris. This is not the case here. A couple of diagnostic features are the inflated pinnules, closely placed venation and all pinnules angled towards the pinna apex. It would be best if the venation pattern could be made out, but with the other features it can be confidently assigned to Acitheca polymorpha. As a side note, the use of the morphogenus Pecopteris is becoming more restricted and it has been broken into several more natural groups. That said this is not a Pecopteris, though it is tree fern foliage.

Hope that helps,

Jack

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