Unknown trace fossil burrow

[Misha]

Here is a fossil shell I found on a fairly recent trip to big Brook nj, towards the right there is a burrow that looks very straight and in the end of one some kind of dark conical figure is located, not sure what it is, any help would be appreciated.

Thank you.

[Wrangellian]

From what I can see, it looks like stems from some kind of plant.

[Misha]

3 hours ago, Wrangellian said:

From what I can see, it looks like stems from some kind of plant.

The thing is, that is a burrow located on a fossil oyster shell. Not sure if it would be possible for a plant to fossilize like that. But thank you either way.

[Wrangellian]

Are you sure that's a shell, not layered sediments?

[Misha]

1 hour ago, Wrangellian said:

Are you sure that's a shell, not layered sediments?

In the Big Brook area where we hunted the fossils had very little matrix material, and also I don't have a picture of it but there is a spot on the other side of the shell where the foot of the mollusc connects to the shell.

[erose]

Definitely a filled burrow in the oyster shell. I have oyters from there with two distinct burrows. The most common are the smaller (1-2mm dia) dense webs of “burrows” made by the sponge Cliona. The others are bigger (3-5mm dia) round bottomed burrows that are always perpendicular to the shell. I always assumed those were made by some other large predatory mollusk. This one is interesting. I suspect the material inside is just matrix.

[Misha]

15 minutes ago, erose said:

The most common are the smaller (1-2mm dia) dense webs of “burrows” made by the sponge Cliona. The others are bigger (3-5mm dia) round bottomed burrows that are always perpendicular to the shell

I have a few shells with burrows, some very interesting.

this one is made by small barnacoe like crustaceans, called Rogerella.and this one which was identified on the forum as most likely being Entobia.

[erose]

Thanks Misha for adding those images and IDs. Pretty sure Entobia is what we called Clionia. And I had completely forgotten about the barnacle borings.

 

[Misha]

1 minute ago, erose said:

Entobia is what we called Clionia

That would make so much sense, I have looked all over the internet trying to find more information about them but there were few distinctions between the different types of borings.

Thank you for the insight.

[Wrangellian]

Ah.. that's what I get for commenting on an area I'm not familiar with! I've got to stop doing that. The straight (non-meandering) shape of the burrow threw me, as did the dark, almost charcoaly appearance of the matrix filling it, which is something you commonly get with plant fossils (eg. carbonized stems).

[Misha]

1 minute ago, Wrangellian said:

Ah.. that's what I get for commenting on an area I'm not familiar with! I've got to stop doing that. The straight (non-meandering) shape of the burrow threw me, as did the dark almost carbon appearance of the matrix filling it, which is something you commonly get with plant fossils.

Don't worry about it, any ideas are appreciated! 

[Wrangellian]

[abyssunder]

Those are borings, I agree with Erich. The dark infill material sometimes is misleading.

[Misha]

23 hours ago, abyssunder said:

Those are borings, I agree with Erich. The dark infill material sometimes is misleading.

Do you know what it could be from?

[abyssunder]

I suppose they are made by polychaetes.