Is This A Stromatoporoid?

[BLT]

Hello, I found this rock in Alabama (Mississippian/Tuscumbia Limestone) and have been trying to figure out what is all over it. After searching the forum and the internet, the closest match I could find is it possibly being a stromatoporoid, showing mamelons? If not, can anyone tell me what it might be? (My husband says it looks like melted plastic to him. I’m really hoping he isn’t correct. Lol) 

 

Thanks!

[BLT]

[BLT]

I’m also wondering if the last two pics could be showing the side view, with either laminae or pillars? If so, I’ve recently posted another item for identification that looks quite similar. 

[grandpa]

Well, I'm pretty sure this isn't a stromatoporid.  They existed in the Silurian and Devonian Periods.  I'm also pretty sure it isn't melted plastic.  What I do think might be a reasonable option is that you have a good specimen of a Mississippian bryozoan.  I'm not a "moss animal" expert, so I'll leave it to those who are to ID the genus and species, but I do know that you have a nice specimen here.  Good find.

[BLT]

1 minute ago, grandpa said:

Well, I'm pretty sure this isn't a stromatoporid.  They existed in the Silurian and Devonian Periods.  I'm also pretty sure it isn't melted plastic.

Thank you!

As long as my husband isn’t right about it being melted plastic, and I do not have to hear, “I told you so!”, then I will be pleased with any type of fossil identification! Lol   

[Mark Kmiecik]

18 minutes ago, BLT said:

Thank you!

As long as my husband isn’t right about it being melted plastic, and I do not have to hear, “I told you so!”, then I will be pleased with any type of fossil identification! Lol   

Not melted plastic, for sure. I get a very bryozoan vibe from it.

[abyssunder]

I'm not sure if stromatoporoid existed only in the Silurian - Devonian.
I'm in the bryozoan camp right now.

[BLT]

4 minutes ago, Mark Kmiecik said:

Not melted plastic, for sure. 

I’m so glad! Lol

 

4 minutes ago, Mark Kmiecik said:

I get a very bryozoan vibe from it.

Gotcha. Thank you!

[BLT]

3 minutes ago, abyssunder said:

I'm not sure if stromatoporoid existed only in the Silurian - Devonian.

Hmm.  I guess that I need to dig a bit deeper. 

4 minutes ago, abyssunder said:

I'm in the bryozoan camp right now.

Thanks! Then that is what i’ll go with for now.

[abyssunder]

13 minutes ago, BLT said:

Hmm.  I guess that I need to dig a bit deeper. 

Thanks! Then that is what i’ll go with for now.

I'm not sure about bryozoan, but it could be a candidate.

[BLT]

2 minutes ago, abyssunder said:

I'm not sure about bryozoan, but it could be a candidate.

Ah, gotcha. Hmm.... 

[Mark Kmiecik]

I think the bumps are too neatly arranged in rows to be mamelons on a stromatoloid. Stromatolites appear to have a less structured morphology.

[grandpa]

25 minutes ago, abyssunder said:

I'm not sure if stromatoporoid existed only in the Silurian - Devonian.

 

Well . . .  I have to reverse my earlier statement.  Digging in deeper, I found  https://ucmp.berkeley.edu/porifera/stromatoporoids.html

from which I quote:  "There are two main groups of fossil stromatoporoids that lived in different eras, the Paleozoic and the Mesozoic. The fossil record of the earlier group begins in the Ordovician and persists until the Early Carboniferous. After their appearance, the Paleozoic stromatoporoids quickly became dominant reef builders, and persisted as such for over 100 million years. They are absent in the fossil record between the Early Carboniferous and the Late Permian. The second group of stromatoporoids, from the Mesozoic, may represent a distinct group with a similar growth form. The Mesozoic stromatoporoids are again important contributors to reef formation, especially during the Cretaceous. Several living sponges would be classified as stromatoporoids in this second group if found as fossils, and these can be assigned to the Demospongia based on soft parts. Their diversity is reflected in the overall diversity of Demospongia through time."

 

Thank for the correction, abyssunder; I learned something. 

 

So, BLT, my apologies, it could be a stromatoporid.

 

[BLT]

5 minutes ago, Mark Kmiecik said:

I think the bumps are too neatly arranged in rows to be mamelons on a stromatoloid. Stromatolites appear to have a less structured morphology.

Oh wow, I hadn’t even considered the arrangement of the rows of bumps. 

[BLT]

4 minutes ago, grandpa said:

So, BLT, my apologies, it could be a stromatoporid.

No worries at all! Thank you for the information.

[FossilNerd]

@BLT I didn’t realize you had posted this too!  

 

Honestly, I’m not sure on this one. It has mounds on the surface that makes me think mamelons and hence Stromatoporoid, but some bryozoa can have bumps like this too called monticules. The specimen doesn’t seem as layered as I’m used to seeing with Stroms. 

 

I think I’m in the bryozoan camp for now, but am not 100% convinced.  Maybe something in the family of Heterotrypidae? I’m not entirely sure they were around during the Mississippian though... 

https://en.m.wikipedia.org/wiki/Heterotrypidae

The openings in the red circled area of your pic below, and the lack of astrorhizae (hole in the top of mamelons) and astrorhizael grooves from the mounds makes me lean towards bryozoa. But these things can be tricky and two stromatoporoid from the same species can actually vary in visible morphology. One could have mamelons and the other not even though they are the same species, or it may have mamelons, but no hole in the top. A microscope is about the only way to determine species for sure.  

 

I’m intrigued! I’ll keep digging!  

 

Some light reading if you care to...  

 

KERSHAW, S. 1998. The applications of stromatoporoid palaeobiology in palaeoenvironmental analysis. Palaeontology, 41, 3, 509–544.

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[caldigger]

Perhaps something similar to this Heterotrypa sp. 

( bryozoan ).

[grandpa]

Does this add any light?

http://faculty.chas.uni.edu/~groves/LabExercise08.pdf

"8–4 Stromatoporoids are unique poriferans that secreted an open calcareous skeleton, or coenosteum, consisting of a network of structural elements perpendicular and parallel to the growth surface (Figures 3 and 4). Single, sheetlike layers parallel to the growth surface are called laminae. Spaces between laminae are called galleries. During life, the galleries may have been filled with sea water or with soft tissue of the organism. Pillars are rodlike elements oriented perpendicular to laminae. Low mounds on the growth surface are termed mamelons. Individual organisms grew in domal, tabular, encrusting, dendroid or digitate shapes. Although stromatoporoids can exhibit a wide range of gross morphologies, all can be identified by their distinctive internal structure."

[See drawing in document - I can't get it to copy and paste.  Notice the astrorhiza on the mamelons.  I can't detect this on the specimen in question, but I may just not be seeing it. ]

"Stromatoporoids and stromatolites (remember them?) superficially resemble one another. They can be distinguished by the presence of vertical elements (pillars) in stromatoporoids, whereas there are no vertical elements in stromatolites.

Paleoenvironmental Range:Stromatoporoids were most common in shallow water, shelf settings. They, along with certain corals, formed massive reefs in the Middle Paleozoic (Silurian-Devonian periods).

Stratigraphic Range:Stromatoporoids originated in Ordovician time, became very diverse and abundant in Silurian and Devonian time, and then apparently became extinct in late Devonian time. Stromatoporoid-like sponges reappeared in the Mesozoic Era, but the lengthy gap between the last Paleozoic forms and the first Mesozoic forms suggests that the morphologic similarity between the two groups may be a product of convergence and not common ancestry.  [What I got confused in my head when I wrote above that they were from the Silurian and Devonian periods - now better understood - I think.]

 

I'm still digging, trying to find some definitive way to differentiate stromataporid sponges from bryozoans.  For now, I'm still thinking bryozoan, but with less certainty.  One thing I am sure of - it's NOT melted plastic!

[BLT]

7 hours ago, FossilNerd said:

@BLT I didn’t realize you had posted this too!  

Lol, I chuckled when I realized we had both been posting essentially the same suggestions at the same time, on different  I.D. requests of mine.

[FossilNerd]

7 hours ago, grandpa said:

Notice the astrorhiza on the mamelons.  I can't detect this on the specimen in question, but I may just not be seeing it.

This is one thing that makes me unsure as well. 

The below paper does suggest that sometimes the mamelons do not have astrorhizae or that some will have mamelons while it’s neighbor may not. See page 13. They may be “simple” animals, but they sure are difficult to ID. 

 

KERSHAW, S. 1998. The applications of stromatoporoid palaeobiology in palaeoenvironmental analysis. Palaeontology, 41, 3, 509–544

[FossilNerd]

17 minutes ago, BLT said:

Lol, I chuckled when I realized we had both been posting essentially the same suggestions at the same time, on different  I.D. requests of mine.

Great minds think alike! 

[BLT]

10 minutes ago, FossilNerd said:

Great minds think alike! 

Indeed, they do! 

[FossilNerd]

7 hours ago, grandpa said:

Stratigraphic Range:Stromatoporoids originated in Ordovician time, became very diverse and abundant in Silurian and Devonian time, and then apparently became extinct in late Devonian time. Stromatoporoid-like sponges reappeared in the Mesozoic Era, but the lengthy gap between the last Paleozoic forms and the first Mesozoic forms suggests that the morphologic similarity between the two groups may be a product of convergence and not common ancestry.

Wait... @grandpa. I think you were right... If I’m reading this correctly. Stroms were around from the Ordovician through the Devonian, then disappeared until the Mesozoic. So they would have been absent in the fossil record during the Carboniferous.

@BLT didn’t you say you found this in Mississippian (early Carboniferous) rock? 

[BLT]

1 minute ago, FossilNerd said:

 

@BLT didn’t you say you found this in Mississippian (early Carboniferous) rock? 

Yes. 

 

I just took pictures of two smaller specimens which I found in the same area. 

[BLT]

7 hours ago, grandpa said:

I'm still digging, trying to find some definitive way to differentiate stromataporid sponges from bryozoans.  For now, I'm still thinking bryozoan, but with less certainty.  One thing I am sure of - it's NOT melted plastic!

I just posted two more photos. Zooming in on the branching lines in the first photo leads me to believe that it is, indeed, some type of bryozoan.