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South Texas Upper Cretaceous Bivalve 2.0


CraigHyatt

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I've posted some of these before, but these are more complete specimens, so maybe possible to get a better ID. I'm finding lots of these, so you can't accuse me of being a lopha.

Found in Eagle Pass, TX. Upper Cretaceous. Found on top of the ground, which is a sandstone layer above layers of soft shale and mudstone. Sphenodiscus and oysters found in this area.

Based on photos I've found similar to what I can see of these specimens, I estimate the total length of the animal at 15 to 20 cm from stem to stern. I am uncertain of the actual shape. Since the specimens I have are somewhat spherical, I assume they are a fragment of both halves of the animal, making the total thickness 4 to 5 cm, and the width 5 to 6 cm.

The orientation is interesting. I've found a half dozen of these. All the ones with the "face" feature are oriented with the "face" positioned on the top and dead center. Assuming the samples were pushed to the surface and weathered top down, then all of the samples came to rest on the bottom oriented the same. This tells me the animal probably has a domed upper half and a flat lower half or the center of gravity caused it to orient itself the same way when it died.

I've seen photos online of frons, travisana, and cristagalli that resemble these specimens one way or another. Not sure these were all present in Cretaceous. Travisana looks most like these two specimens. The cristagalli I saw has the peculiar "deaths head" face feature.

I have provided a top view and 360 degree view of each new specimen 3 & 4 and a comparison with the older specimens 1 & 2.

New Specimen 3 Detail

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New Specimen 4 Detail

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Compare Old 1 & 2 w/ New 3 & 4

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Info: Craig Hyatt, retired software/electrical engineer

Experience: Beginner, fossil hunting less than a year

Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert

Formation: Escondido, Marine, Upper Cretaceous

Materials: Sandstone, Mudstone, Shale, Chert, Chalk

Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus

Reference: http://txfossils.com/Txfossils.html

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There's nothing to say about the pictures, because they're great and comprehensive, and the specimens are intriguing, although they give me a strong geological vibe.
I'm not familiar with the area of El Paso del Aguila, but if I'm correct is in Maverick County, part of the Maverick Basin which is part of Texas karst and pseudokarst regions.
In my thinking your specimens could be similar to the large variety of Speleothems, like the lamellar ones : https://www.google.com/search?q=lamellar+speleothem&biw=1360&bih=612&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiGlab24-nMAhWLIcAKHWCoC9EQ_AUIBigB#tbm=isch&q=speleothem&imgrc=XaxvVUX2GmJsbM%3A

" We are not separate and independent entities, but like links in a chain, and we could not by any means be what we are without those who went before us and showed us the way. "

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I agree, the cleaning and new images are very nice. It's a lot easier to see the details. I'm a bit at a loss regarding the fossil connection, now...they may be geologic in origin.

Is there any shell material found on any of the surfaces or mixed into the matrix features?

The human mind has the ability to believe anything is true.  -  JJ

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"... cave bacon ..."

Wouldn't surprise me. About 90% of the fossils I find turn out bogus. The missus and I actually saw some cave bacon in Timpanogos caves in Utah. It made me hungry. :-)

P.S. Every time I read your neutrino tag line, I think "There must exist a magnetic monopole." :-)

Info: Craig Hyatt, retired software/electrical engineer

Experience: Beginner, fossil hunting less than a year

Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert

Formation: Escondido, Marine, Upper Cretaceous

Materials: Sandstone, Mudstone, Shale, Chert, Chalk

Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus

Reference: http://txfossils.com/Txfossils.html

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I agree, the cleaning and new images are very nice. It's a lot easier to see the details. I'm a bit at a loss regarding the fossil connection, now...they may be geologic in origin.

Is there any shell material found on any of the surfaces or mixed into the matrix features?

Just to be clear, 3 & 4 are brand new specimens. I didn't clean them other than washing off the mud. I don't see any shell material; the matrix looks like a homogeneous fairly soft sandstone. They have a thin reddish coating that's a bit deceptive in that it looks like chitin, but I see that same coating on rocks.

I'll try to remove some of the matrix to see if the specimen is embedded in the surrounding material or if the whole thing is just a cast.

Let me post a couple of magnified views. Maybe there will be some tell tale texture visible.

In my opinion, the cross section and dimensions of the ridges (what I called "legs" when I thought these were crabs) is very similar to the other specimens I've found.

These new 3 & 4 specimens are definitely more 3D compared to the flatter 1 & 2.

Info: Craig Hyatt, retired software/electrical engineer

Experience: Beginner, fossil hunting less than a year

Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert

Formation: Escondido, Marine, Upper Cretaceous

Materials: Sandstone, Mudstone, Shale, Chert, Chalk

Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus

Reference: http://txfossils.com/Txfossils.html

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Here's a comparison of two older specimens (1 & 2) against the two new specimens (3 & 4). One thing I just noticed is that 3 has the "face" feature I saw on 1 & 2, but half of the feature is worn away. I don't know if 4 has the feature, but there's a big spot in the middle that's completely obliterated (I might see the "eyebrows" in 4 but could be my imagination). Presence of the "face" leads me to believe that 1, 2, and 3 aren't geological.

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Info: Craig Hyatt, retired software/electrical engineer

Experience: Beginner, fossil hunting less than a year

Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert

Formation: Escondido, Marine, Upper Cretaceous

Materials: Sandstone, Mudstone, Shale, Chert, Chalk

Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus

Reference: http://txfossils.com/Txfossils.html

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Here are some magnified views taken through a hand lens. These are all from new specimen 3. This is the new one that I just noticed has the "face" feature.

Close ups of ridges showing surface texture and ridge geometry.

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The face feature.

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End view of a broken ridge.

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Info: Craig Hyatt, retired software/electrical engineer

Experience: Beginner, fossil hunting less than a year

Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert

Formation: Escondido, Marine, Upper Cretaceous

Materials: Sandstone, Mudstone, Shale, Chert, Chalk

Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus

Reference: http://txfossils.com/Txfossils.html

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A few random images from the Internet. Different parts of some of these resemble the specimens at hand.

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Info: Craig Hyatt, retired software/electrical engineer

Experience: Beginner, fossil hunting less than a year

Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert

Formation: Escondido, Marine, Upper Cretaceous

Materials: Sandstone, Mudstone, Shale, Chert, Chalk

Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus

Reference: http://txfossils.com/Txfossils.html

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and one magnificent piece,much cited,by the late great dolf seilacher:

REQUIRED READING!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

http://www.palass.org/publications/palaeontology-journal/archive/27/2/article_pp207-237

Thanks so much. I love the scholarly papers. Well, mostly I look at them purty pitchers. :-)

I'm driving down to Laredo today, and while driving, I was thinking about why Lophas evolved those high sharp ribs. I think mostly they provide strength while minimizing material and weight. A more intriguing idea is that they act as crushable shock absorbers. In other words, if the animal is dropped or bitten, the ribs partially collapse and absorb the force. Interesting that they are triangular, which gives good strength with less material, like a corrugated container. Also, when the edges wear, the shell might become sharp like a serrated blade to discourage predators. I suppose they also keep predators from pulling him out of his burrow, so they act like barbs.

Info: Craig Hyatt, retired software/electrical engineer

Experience: Beginner, fossil hunting less than a year

Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert

Formation: Escondido, Marine, Upper Cretaceous

Materials: Sandstone, Mudstone, Shale, Chert, Chalk

Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus

Reference: http://txfossils.com/Txfossils.html

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wasn't finished yet :P

http://www.bioone.org/doi/pdf/10.2110/palo.2005.p05-48

the Seilacher piece has purdy pitchers!

Already scanning through it while having my coffee at McDonalds. Man, I need to upgrade my iPhone to one of those big ones. From what I can see, the paper is a masterpiece. Could have been written by an engineer. :-)

I'll print it out when I get back home today.

Time to hit the road.

Info: Craig Hyatt, retired software/electrical engineer

Experience: Beginner, fossil hunting less than a year

Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert

Formation: Escondido, Marine, Upper Cretaceous

Materials: Sandstone, Mudstone, Shale, Chert, Chalk

Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus

Reference: http://txfossils.com/Txfossils.html

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I was thinking about why Lophas evolved those high sharp ribs. I think mostly they provide strength while minimizing material and weight. A more intriguing idea is that they act as crushable shock absorbers. In other words, if the animal is dropped or bitten, the ribs partially collapse and absorb the force. Interesting that they are triangular, which gives good strength with less material, like a corrugated container. Also, when the edges wear, the shell might become sharp like a serrated blade to discourage predators. I suppose they also keep predators from pulling him out of his burrow, so they act like barbs.

Hey, the editor scripts are working for me today!

Anyway... you are thinking like an engineer now. :D Yes, I think the surface convolutions minimize material and maximize strength, just like corrugations used in steel. But more importantly I think it minimizes the surface area contact that sea star and octopus can use to pry open the shell. Those are likely the chief predators of these bivalves. http://www.asnailsodyssey.com/LEARNABOUT/CLAM/clamDef2.php

Some bivalve use spines to push off the arms of octopus and sea stars. Other bivalves conceal themselves in the mud or sand. The bivalves that live above the mud or sand often have some type of defense such as thicker shells (like Mercenaria) or surface ornamentation.

EDIT: Well, Mercenaria lives below the surface, so that was a bad example...

There was a book written a couple decades ago about the engineering analysis of dinosaurs that you might like. I can't remember the title, but I have it in a pile in the back room somewhere. Maybe somebody knows that books.

Evolution is a marvelous and quirky engineer. :)

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Those are some nice finds. Way out of my time period and I've never seen the like before. I would like to ask a question about them, respectfully, if I may? What is telling you that they are bivalves? What do you look for? There is no joint where the 2 valves meet that I can see. If it's there and I am not recognizing it could you point it out to me?

They do look crabby. I was thinking horseshoe crab sheds, but I don't see any joints. They also remind me of conch egg cases, but bigger. Those are soft and wouldn't fossilize well so that isn't a possibility. Could they be the internal whorls of a type of gastropod after the outer shell has worn away? Just throwing that out there :)

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Those are some nice finds. Way out of my time period and I've never seen the like before. I would like to ask a question about them, respectfully, if I may? What is telling you that they are bivalves? What do you look for? There is no joint where the 2 valves meet that I can see. If it's there and I am not recognizing it could you point it out to me?

They do look crabby. I was thinking horseshoe crab sheds, but I don't see any joints. They also remind me of conch egg cases, but bigger. Those are soft and wouldn't fossilize well so that isn't a possibility. Could they be the internal whorls of a type of gastropod after the outer shell has worn away? Just throwing that out there :)

I'm wide open. On another thread, bivalve was the general consensus. There are no joints visible. Coincidentally, my wife was eating crab legs at the time. Not only were the joints prominent, but the legs had spines.

When I searched Cretaceous Lopha images I saw a lot of possible matches. In particular, one of the Lopha frons images was a dead ringer for my earlier two finds. For me, that was the clincher.

What would nail it for me would be a photo matching the distinctive "face" feature. Others have suggested this might be a hinge feature.

But I'm a total newbie, so I'm listening to you experts. :-)

Info: Craig Hyatt, retired software/electrical engineer

Experience: Beginner, fossil hunting less than a year

Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert

Formation: Escondido, Marine, Upper Cretaceous

Materials: Sandstone, Mudstone, Shale, Chert, Chalk

Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus

Reference: http://txfossils.com/Txfossils.html

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I'm wide open. On another thread, bivalve was the general consensus. There are no joints visible. Coincidentally, my wife was eating crab legs at the time. Not only were the joints prominent, but the legs had spines.

When I searched Cretaceous Lopha images I saw a lot of possible matches. In particular, one of the Lopha frons images was a dead ringer for my earlier two finds. For me, that was the clincher.

What would nail it for me would be a photo matching the distinctive "face" feature. Others have suggested this might be a hinge feature.

But I'm a total newbie, so I'm listening to you experts. :-)

Don't confuse me for an expert on anything Cretaceous. That's way, way out of my area of collecting. But I did remember something that looks close to what you have. You say you find your specimens in areas with oysters. Rays would be happy in shellfish rich areas. I have seen shoals of pregnant rays washed ashore in NC after strong storms. This could be a similar situation. It would work beautifully except that rays are cartilaginous fish. Like sharks they rarely fossilize. A great way to justify the impossible!

BTW those are called Jenny Hanivers if you've never seen one before. Dried out ray bodies.

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Don't confuse me for an expert on anything Cretaceous. That's way, way out of my area of collecting. But I did remember something that looks close to what you have. You say you find your specimens in areas with oysters. Rays would be happy in shellfish rich areas. I have seen shoals of pregnant rays washed ashore in NC after strong storms. This could be a similar situation. It would work beautifully except that rays are cartilaginous fish. Like sharks they rarely fossilize. A great way to justify the impossible!

BTW those are called Jenny Hanivers if you've never seen one before. Dried out ray bodies.

They definitely have the scary face. :-)

Being a non-specialist is a plus. More likely to think outside the box.

On drive home, I've been thinking. I think the next step is to try and expose more of the fossil. Some of them are in softer sandstone, so I might be able to do it. Or maybe talk my wife into it. She has awesome hand skills and is a lot more patient than me.

BTW I'm a North Carolina boy, born and raised. NCSU grad. Go Pack! :-)

Info: Craig Hyatt, retired software/electrical engineer

Experience: Beginner, fossil hunting less than a year

Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert

Formation: Escondido, Marine, Upper Cretaceous

Materials: Sandstone, Mudstone, Shale, Chert, Chalk

Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus

Reference: http://txfossils.com/Txfossils.html

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I don't think this is geological, it seems more biological to me.

To think outside the box of this being a bivalve, take a look at this ichnofossil that looks like a feeding trace to me. Notice the center of the digging has a "face" to it. This ichnofossil came out of a paleozoic formation, so it wouldn't be the exact same creature, but maybe something similar.

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The photo above is from the Dry Dredgers site... http://drydredgers.org/fieldtrips/trip200309p4.htm

The "totenkopf" seems to consistently appear at the center of these "arms", and I think it might be the mouth, or some other feature on the bottom of the feeding animal, and the arms are the dug trenches. So what type of animal might be feeding by digging in the mud? Or was it hiding? A crab? What else?

Until further notice, this fossil will be given the informal name of "The Hyatt Monster of Eagle Creek". :D

EDIT: The ichnofossil shown above is likely a cast, so it is being shown up-side-down.

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I don't think this is geological, it seems more biological to me.

To think outside the box of this being a bivalve, take a look at this ichnofossil that looks like a feeding trace to me. Notice the center of the digging has a "face" to it. This ichnofossil came out of a paleozoic formation, so it wouldn't be the exact same creature, but maybe something similar.

attachicon.gifradial.jpg

The photo above is from the Dry Dredgers site... http://drydredgers.org/fieldtrips/trip200309p4.htm

The "totenkopf" seems to consistently appear at the center of these "arms", and I think it might be the mouth, or some other feature on the bottom of the feeding animal, and the arms are the dug trenches. So what type of animal might be feeding by digging in the mud? Or was it hiding? A crab? What else?

Until further notice, this fossil will be given the informal name of "The Hyatt Monster of Eagle Creek". :D

EDIT: The ichnofossil shown above is likely a cast, so it is being shown up-side-down.

Now that's the first thing I've seen that has the face feature and very similar ridges. That one is very high on the list of likely suspects. The face feature looks almost identical. I am going to research ichnofossils to see if I can find a match.

Info: Craig Hyatt, retired software/electrical engineer

Experience: Beginner, fossil hunting less than a year

Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert

Formation: Escondido, Marine, Upper Cretaceous

Materials: Sandstone, Mudstone, Shale, Chert, Chalk

Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus

Reference: http://txfossils.com/Txfossils.html

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You are on to something. I searched ichnofossil feeding and saw a bunch of good candidates. Feeding trench casts also answers my question about why the thing always managed to die in exactly the same orientation.

Edit: Now searching things like Cretaceous mouthparts, Cretaceous crustacean, Cretaceous arthropod, etc. For the ichnofossil theory, I think the "face" would be a positive cast of the mouth parts. I can imagine a thing with a lot of sharp pointed feet that scrape in toward the centerline (the way trilobites feed). That would explain the triangular shape of the trenches and more or less consistent spacing (noting that the trenches become ridges in the positive cast).

BTW, I solved a separate mystery as well. I see these things all over the place, and now I know they are casts of feeding trenches.

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Ixa cylindrus (extant species, but good match)

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Info: Craig Hyatt, retired software/electrical engineer

Experience: Beginner, fossil hunting less than a year

Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert

Formation: Escondido, Marine, Upper Cretaceous

Materials: Sandstone, Mudstone, Shale, Chert, Chalk

Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus

Reference: http://txfossils.com/Txfossils.html

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The first ichnofossil I ever found was a nice trilobite feeding trench. I didn't know what it was, and I attempted to excavate underneath it to "find the bottom". Since these ichnofossils are casts and molds, they have no "bottom", and I mangled my fossil up a bit learning that.

I also have a nice sea star feeding ichnofossil. Stars will sit in one spot and fail their arms, picking up tiny pieces of the sediment off the bottom, tasting the particles to look for food. They leave a fuzzy star impression ichnofossil.

So many activities can be fossilized, feeding, burrowing, just walking. Each activity is given its own scientific classification name. So a ichnofossil can have one classification name for the activity, and another for the creature that made it (if the creature can be known).

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I don't think this is geological, it seems more biological to me.

To think outside the box of this being a bivalve, take a look at this ichnofossil that looks like a feeding trace to me. Notice the center of the digging has a "face" to it. This ichnofossil came out of a paleozoic formation, so it wouldn't be the exact same creature, but maybe something similar.

attachicon.gifradial.jpg

The photo above is from the Dry Dredgers site... http://drydredgers.org/fieldtrips/trip200309p4.htm

The "totenkopf" seems to consistently appear at the center of these "arms", and I think it might be the mouth, or some other feature on the bottom of the feeding animal, and the arms are the dug trenches. So what type of animal might be feeding by digging in the mud? Or was it hiding? A crab? What else?

Until further notice, this fossil will be given the informal name of "The Hyatt Monster of Eagle Creek". :D

Pssh. That's not a monster. This is a monster. :-)

post-20989-0-66308100-1463933719_thumb.jpeg

Info: Craig Hyatt, retired software/electrical engineer

Experience: Beginner, fossil hunting less than a year

Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert

Formation: Escondido, Marine, Upper Cretaceous

Materials: Sandstone, Mudstone, Shale, Chert, Chalk

Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus

Reference: http://txfossils.com/Txfossils.html

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