Waccamaw Bryozoan

[ClearLake]

A few months back I won an auction from @sixgill pete and part of the lot was a bag of matrix from the Waccamaw Formation in Columbus County North Carolina.  The Waccamaw Fm. is a marine sand and shell hash that has been correlated numerous different ways with a varying range of ages applied to it in the past, but as it is currently interpreted, it is Pleistocene in age (Gelasian and Calabrian Stages or Upper Blancan to Irvingtonian if you prefer the NA names) and found in South Carolina and southeastern North Carolina.

 

The bag was chock full of molluscan goodies and I am steadily working through the identification of those.  One thing that caught my eye amongst all the shells were these little saucer shaped bryozoans similar to Lunulites except that most had a little grain of sand at their center.  They are small (generally 2-3 mm in diameter, largest one is 7 mm across), but there were several hundred of them. After staring at them under the microscope for long enough, I recognized that there were at least two different types in here.  Here is a shot of my sorting tray with all of them in there.

A quick check of the two great publications I have from the North Carolina Fossil Club gave me some excellent pictures but three different names.  A check of WORMS showed me that only one of those names was currently accepted so I began my search to see what was what knowing full well that bryozoan identification can be difficult and involves a lot of terminology that I am not well versed in (I have to admit, when ID’ing my collections, I am prone to lump the Paleozoic bryozoans from a given locality in one container and just be satisfied with that).  A search of threads on the Fossil Forum led me to a couple where they were mentioned, but no defining pictures or ID’s.  

 

Here are a few pictures of what we are dealing with and I will apologize right from the start for the poor quality pictures.  I really have to get a better setup for taking microfossil pictures since I tend to deal with small stuff a lot.  I have decent microscope where I can look at them, but it is not set up for pictures.  These are the two more easily identifiable forms, the picture on the right shows two of the same species but in one you can see the sand grain that is the starting point for the bryozoan, it sometimes gets covered or lost in growth and/or fossilization.

 

So, after gathering and reading through a bunch of references from the early 1900’s onward I think I have the correct ID and most current name, but am open to any suggestions from those familiar with these little creatures.  At the very least, hopefully this can serve as a helpful guide to someone who may have come across these, but struggled to put a name to them.  There is a great publication by Canu and Bassler (1923) called North American Later Tertiary and Quaternary Bryozoa which provides lots of information, plenty of descriptions and enough illustrations to find both of the forms I had recognized.  Specifically, they identified a species called Cupularia denticulata from the Waccamaw Fm and its description matched the form on the right above (just to make things interesting, there was another genus of similar bryozoa called Cupuladria, yes, just one letter different – ugh!). From this publication I had a potential name for the two types, could see where the names in the NCFC publications were coming from, and just had to track down what had changed in the intervening almost 100 years.

[ClearLake]

Fast forward to 1965 when Patricia Cook published two papers in the Bulletin of the British Museum called Polyzoa From West Africa The Cupuladriidae (Cheilostomata, Anasca) and Notes on the Cupuladriidae (Polyzoa, Anasca) which detailed the growth history, morphology and taxonomy of the group and specific to my fossils, put Cupularia denticulata into Cupuladria owenii and renamed the genus of my second form.  In 1984 a couple of Polish authors (Baluk and Radwanski) described a new genus within the family Cupuladriidae called Reussirella and assigned multiple species to it including Cupuladria owenii.  And finally in 1994 Cook and Chimonides published a paper called Notes on the family Cupuladriidae (Bryozoa), and on Cupuladria remota sp. n. from the Marquesas Islands which reorganized the systematics and created clearer definitions of the genera within the family. 

 

So with that we are left with the final answer (descriptions based on the literature but relevant to these Waccamaw fossils):

Reussirella owenii – small (generally less than 5 mm), cup shaped, concave basal surface with no visible pores that is often glossy, no covering over most of the zooids and often with small denticles (particles) within the zooids (see the specimen on the left in the three pictures below).  Note that size alone does not define these two, I just happened to pick well preserved specimens that were not the same size.

Discoporella umbellata – a bit larger (5-15 mm), cup shaped, concave basal surface with no visible pores, larger zooids with a covering over most of it just leaving an opening on the distal edge, pores within the zooecial covering (see the specimen on the right in the three pictures below)

 

[ClearLake]

[ClearLake]

Possible Reussirella doma – small (generally less than 5 mm), distinctly dome shaped, flat basal surface with bumps but no visible pores, no covering over most of the zooids.  This species is very similar to R. owenii and I am less certain that the half dozen that I have ID’d are really this.  Some of the features can be found in specimens of either species, but my separation is based on a combination of features listed above.  The two pictures below attempt to show the distinctive features (R. owenii on left, R. doma on right in each picture) of more domal structure, flat base with bumps compared to R. owenii.

 

The diagram below is from Cook (1965) and shows some important distinctions in the shape and features of the individual zooids which you can see under a microscope but can not clearly see in my pictures of specimens.  Reussirella owenii is “C” in the diagram and Discoporella umbelatta is “H”.  The picture is two specimens of mine with individual zooids circled so you can maybe see how they favorably compare with the diagram.

[Tidgy's Dad]

Fascinating story of research and such beautiful little things. 

[ClearLake]

I should point out, since I mentioned it early on, the North Carolina Fossil Club publication Fossil Invertebrates and Plants (Vol. 1) has Discoporella umbellata correctly named but the other one labelled Discoporella denticulata (pg 133) I believe should be called Reussirella owenii.  This poor little guy has had at least a half dozen different genera applied to it and a couple of species names, so keeping up with the changes is very difficult.

[ClearLake]

4 minutes ago, Tidgy's Dad said:

Fascinating story of research and such beautiful little things

Thanks, yes, I may have gotten a bit carried away on this one.  haha  And they are very neat looking under magnification, I wish the pictures could show it as well.

[Coco]

Very interesting research, although the technical words escape me. I have Lower Pliocene in my area and I am unable to differentiate and identify them...

 

Coco

[Al Dente]

These are interesting little bryozoans. The larvae of some species have the ability to select sand grains of a certain size and mineralogy to attach to. There is a paper that describes this titled “ Larval selection of substrate by the Bryozoa Discoporella and Cupuladria”. Another odd thing is the ability of adult colonies to walk around on the substrate using bristles that grow out of the colony. Not something I would imagine a colony of bryozoa doing.

 

In the Pliocene Yorktown Formation some very delicate colonies are found that are very thimble shaped. I can’t help keeping every one I find. I’ve found colonies of these in modern sand on the sound side of the Outer Banks. I thought they were modern colonies but might be reworked Pleistocene.

[ClearLake]

6 hours ago, Coco said:

Very interesting research, although the technical words escape me

Yes, that can be a huge problem.  It could get a bit frustrating when reading a sentence in a paper and I would have to look up every other word!  Steep learning curve!

[Al Dente]

I took some photos of some from the Rushmere Member of the Yorktown Formation. On these, the quartz grain is usually covered up but this photo shows it partially exposed.

 

 

[ClearLake]

6 hours ago, Al Dente said:

There is a paper that describes this titled “ Larval selection of substrate by the Bryozoa Discoporella and Cupuladria

Well, that sent me off reading some more!  One interesting thing it noted was the ones they studied did not seem to like carbonate grains even when that was the predominant minerology.  Thanks, very interesting.  Led me to another interesting paper on these guys about modes of reproduction: some colonies are formed by sexual reproduction (embryo landing on sand grain as shown) but many colonies form by fragmentation of an original colony, either purposefully or by mechanical breakage and you can ID this by looking at their growth pattern.  Interesting stuff!!  In looking at mine, the vast majority have a sand grain you can see.

 

28 minutes ago, Al Dente said:

I took some photos of some from the Rushmere Member of the Yorktown Formation

Very nice photos, that is definitely something I need to work on is my photography skills.  Those do not appear to have obvious pores in the basal surface from what I can see, so they are not a Cupuladria and I don't see coverings on the individual zooids, so they shouldn't be Discoporella.  But they don't appear to have denticles in the zooids so they are probably some species of Reussirella other than R. owenii.  I have seen a couple of these in the Lee Creek matrix I received from @sixgill pete but I have not looked at those very closely yet, they may be similar to what you showed above.

 

I guess I should also point out that there were three papers by Herrerra-Cubilla and others (2006, 2008, 2014) on recent Cupuladriidae from the Panama area that are quite interesting but they specifically do not cover the most common species I had found (R. owenii) and they promise a fourth paper that was supposed to pull it all together between the recent and fossil material, but as far as I know that one has not been published yet.  They also introduce some taxonomy that seems a bit confusing to me, but I may just be missing the nuances.  More to learn!

[Al Dente]

1 hour ago, ClearLake said:

Very nice photos, that is definitely something I need to work on is my photography skills. 

 

1 hour ago, ClearLake said:

Led me to another interesting paper on these guys about modes of reproduction: some colonies are formed by sexual reproduction (embryo landing on sand grain as shown) but many colonies form by fragmentation of an original colony, either purposefully or by mechanical breakage and you can ID this by looking at their growth pattern. 

I took these photos with my smartphone. Here’s an example of a fragment of an original colony that continued to grow into a new colony. One photo is taken with my phone through a microscope eyepiece, the other is just the phone. I have a Galaxy S9 phone and am happy with the camera.

 

 

[Coco]

What is its size ?

 

Coco

[Al Dente]

1 hour ago, Coco said:

What is its size ?

 

Coco

6 millimeters long.