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ced0015

Cretaceous invert or plant (maybe)??

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ced0015

I have no idea what this is. Found in NE Mississippi (cretaceous). Potential invert, or plant? IMG_1989.thumb.JPG.6e759d5c45519fa2b8016b419357a3be.JPGIMG_1988.thumb.JPG.99790cfb6ab6af961e0c9b4d4b68f34c.JPG

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Herb

maybe a burrow?

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GeschWhat

Very interesting! Welcome to the forum :yay-smiley-1:

 

 It does look like some sort of ichnofossil, but exactly what, I couldn't say.

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ced0015
11 minutes ago, GeschWhat said:

Very interesting! Welcome to the forum :yay-smiley-1:

 

 It does look like some sort of ichnofossil, but exactly what, I couldn't say.

thanks!

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abyssunder

Ichnofossil.
It could be interpreted in many ways.
I'm leaning toward something related to bee-like insects considering the bulbous/club-shaped forms and a possible network between them. Really hard to say, maybe something along Celliforma - Fictovichnus  ichnogenus. I'm pretty sure that I see somewhere this kind of trace fossil, but I can't remember where. Also, Treptichnus could have this kind of burrow (sinuous or looping ropes), trying to make sucessive probes to the surface.

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Carl

I'm pretty sure these are lithophagid boring steinkerns. Lithophagids are bivalves that bore into things like other shells from dead bivalves. Your piece would represent the sediment that filled the burrows and lithified before the host substrate eroded away. The parallel lines in the 'bulbs' would represent the growth layers in the cross-section of the host shell. We see these in the marine Cretaceous of NJ. Nice find!

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ced0015
1 hour ago, Carl said:

I'm pretty sure these are lithophagid boring steinkerns. Lithophagids are bivalves that bore into things like other shells from dead bivalves. Your piece would represent the sediment that filled the burrows and lithified before the host substrate eroded away. The parallel lines in the 'bulbs' would represent the growth layers in the cross-section of the host shell. We see these in the marine Cretaceous of NJ. Nice find!

After a little googling, I tend to agree with you. Super cool! Thanks!

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Plax

teredoes were my first thought but then I saw the cliona associated so I agree with Carl (of course) because he's right:)

  that must have been a thick shell

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Carl
2 hours ago, Plax said:

teredoes were my first thought but then I saw the cliona associated so I agree with Carl (of course) because he's right:)

  that must have been a thick shell

Right! I'd totally missed the Cliona!

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abyssunder

As I said, it could be interpreted in many ways.

I don't think they are clionaid boring infills in hard substrate like shells or rocks. It will be a little difficult to see how the support matrix (originally harder in consistence) is totally eroded away leaving only the infill material preserved. Also they are more reduced in size compared to the specimen in question.

Other variant would be the more larger Gatrochaenolites infilled borings, same remark about the preservation as in the previous clionaid.

Teredolites or petrified teredinid boring infills in wood would be a good candidate, as Carl said, although, I don't see the characteristic 'segmentation' pattern which is predominantly transverse to the axis (or ornaments of the texture of the woody substrate).

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Plax

We commonly get cliona and lithophagid burrows preserved when the shell has dissolved away. Sometimes the steinkern has a network of clionid burrows all over the exterior. An American 1 cent piece (penny) is about 19mm. We also occasionally get teredolites without the wood they were originally in.

  I think the lines on the bulbous ends of the gastrochaenolites may actually represent the shell ornamentation of the boring pelecypod.

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Carl

Both Cliona and lithophagid borings (Gastrochaenolites, as named by abyssunder) are also quite common in the NJ Cretaceous. You can see some nice examples here with and without the host shell: http://www.newjerseypaleo.com/fossilsbyera/cretaceous-fossils/cretaceous-porifera/clionidae. And they are remarkably durable. Whatever matrix infilled the galleries and lithified is left after the erosion of the host shell (sometimes some shell remains). I suspect this erosion is primarily chemical as real shell material in some of the horizons is very rare but steinkerns are very common. Chemical erosion could very easily remove all the shelly parts from deep between the Cliona tunnels. As for the ornamentation being preserved I would vote against this because lithphagids excavate their borings with the help of acid secretions that would not likely preserve that kind of detail.

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Plax

I had some lithophagid shells in siderite from the Woodbury Fm which has aragonitic preservation. They were quite ornate but too fragile to survive the trip to NC in '92. they looked like modern angel wing sea shells. I'm suggesting that the ones in the OP are pseudomorph representations of the shell; and poor ones at that. I didn't know that lithophagids used acid I thought they ground their way through their host. Learn something new every day!

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Plax

a picture is worth a thousand words. thanks Al!

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Carl
6 hours ago, Plax said:

I had some lithophagid shells in siderite from the Woodbury Fm which has aragonitic preservation. They were quite ornate but too fragile to survive the trip to NC in '92. they looked like modern angel wing sea shells. I'm suggesting that the ones in the OP are pseudomorph representations of the shell; and poor ones at that. I didn't know that lithophagids used acid I thought they ground their way through their host. Learn something new every day!

Lithophagids use acid but pholadids physically grind, as you say. And angelwings are pholadids - maybe that's what you found?

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Carl
5 hours ago, Al Dente said:

Here's a couple examples I have of bored clam shells that have dissolved away. The first has a lithophagus clam near the top and filled cliona borings. The second just cliona. This is Eocene Castle Hayne Formation from NC.

litho.jpg

sponge.jpg

A perfect reference!

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abyssunder

Good pictures, Al Dente! Fair enough to conclude properly.
In conclusion, the OP's specimen is ichnofossil, combined Gastrochaenolites + Entobia, preserved infilled tunnels, with the hard substrate eroded away.

BTW, clionaids may attack living or non-living shells or pebbles, making regular-shaped circular holes on the surface not by drilling but secreting chemicals (acids) to penetrate the calcium-based substrates on which they live, releasing amoebocytes.

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