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Fossiling on the Ides of March

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PA Fossil Finder

And here's an unknown. Is this a Ceraurus trilobite's cephalon? Or a spiny brachiopod?

unknown.thumb.JPG.662aab66a6c37ba23f75c67bfd2dcc97.JPG

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PA Fossil Finder

With plenty of daylight left, we decided to head out to a second site, the Montour Preserve fossil pit. Some 40 or so minutes later we arrived, seeing the familiar gray slopes of this Devonian Mahantango formation site. Unfortunately, we didn’t find much of anything. Elementary school trips have stripped the site clean of most fossils. I was hoping the freeze-thaw of a good cold winter would help expose new material, but we didn’t find anything. I did pick up some little round concretions – most people skip them over, but I’ve found that they occasionally contain nice large inarticulate brachiopods like Lingula
Disappointed, I decided on a last resort and headed out to a third site – another Mahantango formation exposure, probably from a different layer than the Montour Preserve. We didn’t stay long here, but we did manage to pick up a couple of straight shelled cephalopods, some branching coral chunks, crinoid segments (including a few neat looking ones that were crushed before burial), gastropods, a few more concretions, and best of all – trilobites! I don’t think any of them were complete, but I did pick up a few nice Eldredgeops rana heads. It’s always fun to find our state fossil, even the incomplete ones. Hopefully they’ll clean up well – I can’t wait until it’s warm enough to do fossil prep outside again. 
Some of the finds:
corals.thumb.JPG.eb3c453833d9db5cec5b6b8385fb2701.JPGcrinoids.thumb.JPG.16cd97a66f320492a17a9c3cce325399.JPGgastropod.thumb.JPG.bc10e0ca6b47731dc0307b939a2d2efb.JPGlingula.thumb.JPG.128d0e9d147a9919be90b6d344d0fbbe.JPGcephalopod.thumb.JPG.e8cdeb505e598d6cd07f42da6bb8202c.JPG

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Ludwigia

Nice finds! The bryozoa on the right appears to be sitting on something which has the shape of an echinoid, but is that possible at this early stage? Hopefully some of those trilobites come out complete.

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Wrangellian

Nice stuff!

Is that a severely bent crinoid stem that looks like an ammonite?

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PA Fossil Finder
1 minute ago, Wrangellian said:

Is that a severely bent crinoid stem that looks like an ammonite?

Yep, that's a crinoid stem. That rock has a bunch of them running through it. I'll probably have to glue it all together though, the rock from that site is very crumbly.

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Wrangellian

Yes, it looks to be!

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ynot

Welcome back!

Nice finds!

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Al Tahan

Woahhhh!! You got my attention with those trilobite parts!! :envy:.......looks like it’s time for me to get the rockhounding in PA book. I’m going to be in PA one time this year. I’ll have to make it count! 

 

Great post! Excellent finds :)

 

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Monica

Nice finds!  I especially like the gastropod :wub:  

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dalmayshun

love the trilobite lace bits...would love to know why they developed, what use they were. I wonder if anyone surmises their origin. 

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PA Fossil Finder
On 3/17/2019 at 5:33 PM, Ludwigia said:

Nice finds! The bryozoa on the right appears to be sitting on something which has the shape of an echinoid, but is that possible at this early stage? Hopefully some of those trilobites come out complete.

I checked the underside of the bryozoans, the two round ones look like they were attached to a rock or other substrate. The wide central one looks like it was attached to a brachiopod shell. 

 

13 hours ago, dalmayshun said:

love the trilobite lace bits...would love to know why they developed, what use they were. I wonder if anyone surmises their origin. 

If I remember correctly, some have proposed that the lace collar was used for filter feeding. The pits don't pass all the way through the shell, though, so I don't know how that would work. Personally, I think it might have been some sort of sensory apparatus - Cryptolithus lacks eyes, so it might have used some other sensory organ to find its way around the Ordovician sea floor. If anyone has a better explanation, I'd love to hear it. 

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Tidgy's Dad
14 minutes ago, PA Fossil Finder said:

I checked the underside of the bryozoans, the two round ones look like they were attached to a rock or other substrate. The wide central one looks like it was attached to a brachiopod shell. 

 

If I remember correctly, some have proposed that the lace collar was used for filter feeding. The pits don't pass all the way through the shell, though, so I don't know how that would work. Personally, I think it might have been some sort of sensory apparatus - Cryptolithus lacks eyes, so it might have used some other sensory organ to find its way around the Ordovician sea floor. If anyone has a better explanation, I'd love to hear it. 

I've heard the sensory apparatus idea and the filter feeding theory, now out of favour. 

A third idea is that it acted rather like a snowshoe, spreading the weight of the animal over a wider area so that it didn't sink into the mud or soft sediments.

Not saying that's true, but I remember the idea. 

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