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Fossiling on the Ides of March


PA Fossil Finder

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It’s been quite some time since my last post here on the forum – more than two years! I missed the forum and it’s good to be back.
This last week was spring break for some colleges in Pennsylvania, mine included. Thursday we saw beautiful sunny weather, warm enough to shed the heavy winter coats we’ve been wearing for months. 
Checking weather forecasts, I was pleased to find that Friday would be similarly warm – sunny and mid sixties to seventies! Perfect fossiling weather! I seized the opportunity. I knew these unseasonably warm temps could be gone as soon as they had arrived and didn’t want to miss a chance like this. 
I drove out with my little brother to a couple of sites I’d visited before. The first was an Ordovician roadcut. I’d been told the rock here was from the Salona formation, but Coburn formation limestone is also known from the area and apparently has similar fossils so I’m not entirely certain on this site’s stratigraphy. 
After about an hour’s drive we arrived at the site – only to be greeted by two nasty pieces of roadkill at the base of the cut! Agh! Thankfully they weren’t near the collecting area and didn’t have a noticeable odor yet. We immediately set to work, crawling carefully up the gentle slope of the cut and checking each irregular chunk of tan limestone. It didn’t take me long to score several fine Cryptolithus trilobites, as well as some neat mushroom-shaped bryozoan colonies and a handful of brachiopods. The trilobites here are usually found with either the horseshoe shaped ventral side or the noselike glabella poking out of the surface of the stone. They will take some prep work to expose fully – I’m hopeful at least one or two of them are complete under all that stone. Most of them are just isolated cephalons or chunks of Cryptolithus collar. After about 45 minutes on the cut we took a break for lunch, stashing our finds in the trunk. Our sandwiches finished, we walked back out for round two! Scrambling over fallen stone, I managed to score two big blocks with multiple trilobites each. The crown jewel was a block with at least 15 Cryptolithus showing! I probably won’t even attempt prepping that one until I’m a little more confident in my abilities. I’d hate to ruin such a great multi-block of trilobites. After another hour or two at the cut, we’d found enough. 
Some of our finds:

5c8eb74a6e3f3_blockwithtwocryptolithus.thumb.JPG.e40be571e1e86de6571a9f2af0919af2.JPG5c8eb756a36e8_trilos3.thumb.JPG.e17c67e28d627ef56515b1df32113654.JPG

Bryozoans:

bryozoans.thumb.JPG.d9fa068eeeeb7f00597c6d8858db28e5.JPG

More trilobites:

5c8eb7716e521_trilos1.thumb.JPG.633c62ce36589c038bd9c2e3ef4d1bcf.JPG5c8eb7bbefdec_trilo2.thumb.JPG.3101696394d967b0e948de6ed394cdf0.JPG

Brachiopods:

brachiopods.thumb.JPG.c4aa0ff9bb93d541e864db521f12b5ce.JPG

 

Continued in next post… 

  • I found this Informative 5

Stephen

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A large hash plate with lots of trilobite bits and other interesting stuff:

5c8eb895c9f30_hashplate.thumb.JPG.eeec371868f4bade84ba35017e4b046f.JPG

And a close up of the plate:

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Here's the block with lots of Cryptolithus. I count at least 15 on there. 

multiblock.thumb.JPG.79007c9027eb6c098e1a15f9d37ea36e.JPG

Here's a closeup:

5c8eb8a0e6609_multiblockcloseup1.thumb.JPG.4bb8f56f39da243a6973b33a578e3903.JPG

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Stephen

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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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Stephen

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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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Stephen

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Finally, here are my trilobites from the Devonian site, a few Eldredgeops rana

trilos.thumb.JPG.ab012b97078758432f161bfde4a3a83f.JPG5c8eba024baa6_trilohead.thumb.JPG.a8597ed9dd6b28ec5b9ae611cb74b7eb.JPG

 

All in all, it was a great way to enjoy the fleeting glimpse of spring before all was plunged back into chilly late winter weather. 

 

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Stephen

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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.

 

Greetings from the Lake of Constance. Roger

http://www.steinkern.de/

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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.

Stephen

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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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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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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. 

Stephen

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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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Life's Good!

Tortoise Friend.

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