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Lake Michigan Trace Fossil?


Pippa

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Hi all, 

Is this a trace fossil, worm holes?   If yes, that would be the first I've found. The holes measure about 1mm to 2mm in diameter. I think it's odd that all of the larger diameter holes are perfectly parallel to each other, while the smaller diameter holes seem to run perpendicular to the larger ones. 

Also, what are the dark thread-like shapes all over this rock. I've never seen those on my finds either.  Rock measures 2cm tall, 1.5cm wide.

Lake Michigan beach find, WI, this could be either ordovician, silurian or devonian. 

TIA!

 

front: 

P1030054.thumb.jpeg.a48f0a290a5e98499a2c51eb4d77d071.jpeg

 

back

P1030058.thumb.jpeg.63fb3ad8e9203469b805c2cbf0b5f296.jpeg

 

bottom

P1030059.thumb.jpeg.1b6eddd68419076cbf250abf0ef976f3.jpeg

 

 

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I think it may be a heavily recrystallised branching coral colony. The second photo shows a pair of corallites branching up from the bottom edge, and the vertical and horizontal markings in the left hand tube look epitheca like.

 

The little thread-like dashes show a beaded structure - possibly dissolved out bryozoan fragments such as fenestellid?

Edited by TqB
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13 hours ago, TqB said:

I think it may be a heavily recrystallised branching coral colony. The second photo shows a pair of corallites branching up from the bottom edge, and the vertical and horizontal markings in the left hand tube look epitheca like.

 

The little thread-like dashes show a beaded structure - possibly dissolved out bryozoan fragments such as fenestellid?

 

Oh, I do think you got this exactly right. So these branching corals would have been tiny colonial horn corals, right? 

Hopefully tomorrow, I'll  find some time to take better close-ups of the open tube that appears to show the epitheca imprint. 

 

By the way, is this then still considered a trace fossil, since most of the coral has been dissolved and what's left is really just an empty mold?

 

Thank you for pointing out that the "threads" have a beaded structure, I hadn't noticed. I bet you're right about Fenestellid bryozoan bits too,  that's exactly what they might look like after falling apart. And they certainly are plentiful enough....

 

Thanks so much!

 

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3 hours ago, Pippa said:

 

 

So these branching corals would have been tiny colonial horn corals, right? 

Hopefully tomorrow, I'll  find some time to take better close-ups of the open tube that appears to show the epitheca imprint. 

 

By the way, is this then still considered a trace fossil, since most of the coral has been dissolved and what's left is really just an empty mold?

Sort of, but "horn coral" is just a colloquial term for a horn shaped solitary coral, most commonly rugose but it can perfectly well be applied to some scleractinians too.

So as a colonial rugose coral, people wouldn't call this a horn coral.

 

"Trace fossils" are just the traces of activity, so tracks, burrows, footprints. The mould of a dissolved out fossil like this is still a body fossil. Actually, there's still a fair bit of recrystallised or mineralised skeleton remaining on this one anyway. :)

 

 

 

 

 

 

Edited by TqB
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