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fossilnut

Fossil Gastropods covered with bryozoan

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fossilnut

This November there were 2 days on the beach when I found over 336 various sizes of gastropods covered with at least 2 different types of bryozoa.  I have found similar gastropods covered with coral from the Pliocene in Florida. These fascinate me (hardly of any interest to others on the beach whose focus is shark teeth) because they have a story: the gastropod dies; a hermit crab occupies the dead shell; bryozoa attaches itself to the shell and begins to cover it.
I had found maybe 5 of these gastropods at the high tide mark prior to these two days. It was in low tide areas that i found the 336 (previously I had searched the same areas and found none. After the 2 days I did not find anymore even in other areas of the beach some distance away. I am aware that id of bryozoa is difficult but perhaps someone can recognize the "bumpy" pimply variety in the picture. But more importantly, I am looking for confirmation that these are indeed fossil (beach finds) and any idea as to their age?  I also found about 15 small individual bryozoan colonies.

DSCN4899.JPG

DSCN4902.JPG

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Plax

These may be pagurized gastropods if the hole has been kept clean. The Pagurid crab (hermit crab) lives in the shell exposing all sides but the opening to epibiont infestation. One can find this type of preservation even where aragonitic shells are not preserved because of the bryozoan coating such as the Castle Hayne Formation. They are found as modern shells with the shell intact under the epis also.

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fossilnut

I marvel at the number that appeared (336) over a 2 day period. Were not there before or after. This beach was re-nourished recently I have heard from 3 miles off shore. I have noted before that some days the beach will have large numbers of olives and Augers and at other times there will be none to be found. I guess it is from direction of wind and waves. Further can anyone comment on the environmental conditions for these hermit crab gastropods to have thrived in these numbers. On the current beach, the hermit crabs I have seen have been in low tidal areas. So would they have been in a relatively calm shallow water environment? @Plax did you suggest that these may be from the Eocene castle Haynie or I am I reading too much into your comment?

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Plax

No; not Castle hayne for sure. Just mentioning that the Castle Hayne has similar and doesn't have the shell preserved; just the shape of the gastropod reflected in the bryozoan covering. In Myrtle Beach you have Late Cretaceous Peedee at the base, then in some sections Pliocene Upper Goose Creek Limestone followed by Pleistocene Waccamaw, Canepatch and Socastee. there may be some Wando around there but have never collected fossils from it myself. Have seen similar examples of gastropods like your in the old quarries (now lakes) in the Goose Creek Limestone in Conway. Should also mention that almost any of the formations may be pumped up onto the beach and most are exposed on the ICM.

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Al Dente

These are common in the James City and Waccamaw Formations (Pleistocene). Could be more recent too. 

hermit crab.JPG

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fossilnut

Wow AlDente that is a beautiful example. Was  it found that way or was it prepped to expose the gastropod? Is the final whorl a part of the exposed snail?  Forgive my uncertainty.  Plax what is the ICM? Is this a reference to the Intracoastal waterway? Thanks for the information. PeeDee sea urchins are starting to show up on the re-nourished beach, One of the easily identifiable ways to spot these was that the final whorl opening was clear. pardon my confusion about Castle Hayne.

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jkfoam

Fossilnut,

 

The animal encrusting your gastropods may not be bryozoa but may be a hydrozoa a class of the phylum Cnidaria.  The really bumpy one may be Hydractinia multispinosa  and the other may be Milleaster incrustans.  I think they are both in the order Milleporida.

 

Jim

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Al Dente
11 hours ago, fossilnut said:

Wow AlDente that is a beautiful example. Was  it found that way or was it prepped to expose the gastropod? Is the final whorl a part of the exposed snail? 

I've prepped several this way to determine which species of gastropod the hermit crab used. It turns out that they used a variety of shells. I prepped this with a pin under a microscope. The final whorl is all bryozoan. That is the benefit of this symbiosis for the crab. When it outgrows the shell, the bryozoan continues to grow with the crab so it never needs a new shell.

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Al Dente
5 hours ago, jkfoam said:

Fossilnut,

 

The animal encrusting your gastropods may not be bryozoa but may be a hydrozoa a class of the phylum Cnidaria.  The really bumpy one may be Hydractinia multispinosa  and the other may be Milleaster incrustans.  I think they are both in the order Milleporida.

 

Jim

I think two of them, maybe all, are Hippoporidra. Here is an interesting clipping from the North Carolina Fossil Club book volume 1 "Fossil Invertebrates, Plants". It show these might be mimics of coral. 

hippo.JPG

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fossilnut

AlDente Sorry i don't Know how to quote you. Thanks for taking the time to respond and providing great information for id. Great prep on the gastropod. The bryozoan's creation of the whorl really adds to the story interest when showing these. Why would bryozoa go to the trouble to mimmic coral I wonder?  For me, these are the things that make the passion for this hobby. There is always something more to learn-more questions to ask to reveal the beauty and complexity of nature even among the smallest of creatures. Thanks for sharing your knowledge.

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fossilnut

jkfoam Thanks for your response. It is interesting the many relationships between gastropods, hermit crabs, bryoza and hydrozoa.  I believe that I did find some like that.

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fossilnut

Any thoughts on the age of these I assume are fossils?

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Plax

I meant to say ICW Fossilnut. Sorry about that!

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