Sponge or concretion?

[KCMOfossil]

I assumed this item was a concretion.  I regularly find fist-sized concretions in the Argentine member of the Kansas City group (Pennsylvanian subsystem). But looking this morning at a comment by @WhodamanHD here I wondered whether what I have is a sponge.  The specimen is about 6 inches across and 4.5 inches from top to bottom.  What do you think?

 

 

 

[Miocene_Mason]

It was @abyssunders picture, I know little more than what I saw in the picture but they do look similar to me.

[Innocentx]

Super interesting! Does the material seem quite hard, maybe chert?

[abyssunder]

Thank you Mason for the good think and respect!
That was a fossil sponge in flint from the UK, here's the topic -

 

- and it looks close to the specimen in question. I haven't a better idea (ID) than sponge, but TFF has now a good expert in sponges. What is sure, is that the OP's specimen looks chertish. I wouldn't rule out the sponge possibility.

[Miocene_Mason]

8 minutes ago, abyssunder said:

Thank you Mason for the good think and respect!

Thanks! I remember my mistakes (like in that thread) better than my correct answers

9 minutes ago, abyssunder said:

TFF has now a good expert in sponges.

Perhaps @Spongy Joe

[abyssunder]

4 minutes ago, WhodamanHD said:

Perhaps @Spongy Joe

That's what I was thinking...

[KCMOfossil]

57 minutes ago, Innocentx said:

Does the material seem quite hard, maybe chert?

Thanks for your input.  It does not seem like chert to me (but I'm not too good at identifying rock).  It is like the limestone which makes up the member in which it was found.  

[Spongy Joe]

This is the sort of fossil where I sidle away quietly, whistling to myself...

 

Not totally sure. It could be a sponge, broadly speaking. However, I'm a little dubious about what looks like sedimentary banding running through it. It's also possible that this is just a chert nodule around a large burrow... it can be very hard to tell without clear morphology, I'm afraid!

[KCMOfossil]

Thanks, Spongy Joe.  I appreciate the evaluation.  This specimen looks a lot like items I find there that are nodules or concretions.  I'll just keep it with the question mark.  Thanks again to you and the others that commented.

[Missourian]

It does look like a chert nodule to me, particularly due to what appears to be a conchoidal fracture surface of the broken away part. You can test for chert by attempting to scratch glass with it.

 

Being from the Argentine, there is a good chance some of the wavy lines on the surface are cross sections of phylloid algae.

 

Plus, as it turns out, sponges (specifically Heliospongia) seem to serve as nuclei for concretion growth in a number of limestone beds. These Heliospongia came from the Argentine:

 

 

I've seen sponges preserved like this in the Argentine, Captain Creek, and (I believe) Spring Hill limestones.

 

I believe these sponges are actually also concretions (yes, a sponge and a concretion) because 1) there seems to be no other silicified fossils with them, and 2) the mishappen shape of some may be due to incomplete silicification, i.e. a concretion formed within the body of the sponge, and ceased before expanding to the outer surface. Perhaps the original opaline silica spicules acted as seeds for growth of silica attracted from fluids within the sediment, but this is just my pet theory for the moment.

[Innocentx]

@KCMOfossil  If your have a good magnifier (maybe 10x), use it on the broken surfaces to look for very tiny fossils.  That might help determine a few things about the chert, etc.

[Plax]

looks like a sponge to me right down to the attachment at the base. The signs of amorphous cavities further support the sponge speculation. I'd defer to spongy joe of course for particulars.

[Missourian]

Does the pointed 'base' show any structure? It could be what the concretion formed around (assuming it is a concretion).

[KCMOfossil]

7 hours ago, Missourian said:

test for chert by attempting to scratch glass with it.

It does scratch glass.

 

7 hours ago, Innocentx said:

If your have a good magnifier (maybe 10x), use it on the broken surfaces to look for very tiny fossils

Using my trusty 10x Belomo I found one small brachiopod (imbedded in the chert) that was inside one of the broken/cracked surfaces. 

 

3 hours ago, Missourian said:

Does the pointed 'base' show any structure?

I don't see any structure in the "base".  By all appearances the "base" could be purely geologic.  

 

Thanks to everyone for the fascinating comments.  I am leaning toward a chert concretion because the only real evidence pointing to sponge is the general shape of the object.  Missourian's information about sponges in the Argentine will cause me to keep my eyes open.  Sponges are still a mystery to me.  

 

Thanks again.

 

 

[Wrangellian]

I would hold onto it, just in case it does turn out to be a sponge. That shape is very suggestive! Keep an eye out for more like that.

[KCMOfossil]

1 hour ago, Wrangellian said:

I would hold onto it, just in case it does turn out to be a sponge.

Thanks for the good advice.  I plan to keep it.  Even if it turns out not to be a sponge, it is a fascinating item.  

[Missourian]

The larger sponges encountered in KC are almost always Heliospongia. If your specimen turned out to be some other kind, it would be unusual indeed. 

[Plax]

have attached a pic of much younger (Castle Hayne Fm, Eocene) and more detailed sponges. Notice that the one on the bottom right has a zone of attachment at its base. I realize that your specimen is less detailed but see signs of amorphous internal cavities (first pic) as well as surface pores. Presence of other animals within sponges is not unusual in my experience.

[KCMOfossil]

11 hours ago, Plax said:

a zone of attachment at its base. I realize that your specimen is less detailed but see signs of amorphous internal cavities (first pic) as well as surface pores. Presence of other animals within sponges is not unusual in my experience

Thanks, Plax.  This makes me hope that someday I can put this specimen in the hands of a sponge expert and see if anything more definite can be said about it.  The comments and the disagreement have helped me look more closely at my specimen, and, as always I have learned  some things.  It's strange how scratching your head can make your eyesight better.

 

Thanks to all of you.

[KCMOfossil]

I returned to the same site on Saturday and found a piece that may contribute to the analysis of my original specimen.  This new item seems to be an extended version of the "base" that is on the original.  @Missourian asked me to see if the original item's "base" had any structure.  This new one does.  It is also chert.  @Spongy Joe thought one possibility was that the original item might be a chert nodule around a large burrow.  So what do you think of this new item?

 

 

 

 

Here is the top of the item:

 

Here are some closeups of the "inclusion" in the "base":

[Spongy Joe]

I'm much more confident for sponge on that one - very nice!

 

 

[KCMOfossil]

On 6/11/2018 at 9:36 AM, Missourian said:

sponges (specifically Heliospongia) seem to serve as nuclei for concretion growth in a number of limestone beds.

I wonder if that is what is happening with this new item.

 

12 hours ago, Spongy Joe said:

I'm much more confident for sponge on that one - very nice

Thanks, Spongy Joe.  I plan to return to the site again to see what else I can find.  It's nice to know that there are sponges there.

[Missourian]

The form of and detail on the organism within your second concretion does strongly resemble Heliospongia. Distinct rows of spicules within the body would cinch it.

 

FWIW, here are various ways silicious concretions may form within or around Heliospongia:

 

 

[KCMOfossil]

1 hour ago, Missourian said:

The form of and detail on the organism within your second concretion does strongly resemble Heliospongia. Distinct rows of spicules within the body would cinch it.

Thanks, Missourian.  I'm glad to have this tentative identification.  Also, I came across your previous post on Pennsylvanian sponges of Kansas and Missouri, and that was helpful too.  Your drawing above enables me to envision what I may encounter in the silicification related to these sponges.  My provisional conclusion is that the original item in this post is a concretion that may have formed around some unknown object, and that the second item is a concretion formed around a Heliospongia.  I look forward to returning to this collecting site with my expanded understanding.  In fact, I think I may now have a better chance for recognizing sponges in general.