Pleistocene Rock Marine Imprint

[ClearLake]

On a recent visit to Key West, Florida I found this imprint in a rock along the shore.  This was a piece of rip rap, so its original location is unknown but I believe most of the fill and rubble in the area was sourced fairly locally (South Florida).  The bedrock at this location is the Pleistocene aged Miami Limestone, which is from the Wisconsinan to Sangamonian stages (<700,000 years) but even in all of southernmost Florida (say Miami and south) the oldest you get is Pliocene.  So, while I don't know the exact age, I'm pretty confidant it is fairly young.

 

The imprint is about 5cm wide by 9 cm long.  Hard to tell in the picture perhaps, but it is probably 3-4 cm deep.  In the picture on the left, you see the whole rock, including the other bivalve casts etc in there.  Looks pretty typical for what I saw in the limestones of that area.  The picture on the right is the impression enlarged.  I did not bring it home with me, so this is the best I can do with pictures. 

 

My first impression was it looked like the impression of an ammonite septal wall, but of course it is much to young for that.  Only other thing I can think of is the impression of the top of some type of coral, maybe a brain coral, but I'm struggling to visualize it as it looks too symmetrical for that.  The detail is pretty neat.  Anyone recognize this?  @digit @hemipristis @Harry Pristis

 

 

 

 

[Rockwood]

Looks like a coral, I don't think it's very brainy though. 

[Harry Pristis]

So, we have a mold of the exterior of a marine creature . . . wow!  This cries out for a cast from the mold!  My best guess is fissurellid, a limpet.  This one would have been highly sculptured, but some species are sculptured, Hemitoma retiporosa is one example.

[ClearLake]

16 minutes ago, Harry Pristis said:

  This cries out for a cast from the mold! 

I know!  Wishing I could have brought it home or had the material to do that during my brief visit!

 

Thanks, interesting suggestion, I will look at that. Maybe I should see if @MikeR has any thoughts/suggestions. 

Edited March 4 by ClearLake

[Al Dente]

Looks like Manicina coral.

[ClearLake]

Hmmm, you coral people set me on a path.  Manicina led me to Mycetophllia and this picture from https://scubadiverlife.com/caribbean-coral-roundup-cactus-coral

 

 

Looking further at the species Mycetophllia lamarckiana led me to this website and the picture below (left) which shows some of the fine detail at the edges that I think I see represented in my picture attached (right).  http://www.coralsoftheworld.org/species_factsheets/species_factsheet_summary/mycetophyllia-lamarckiana/

 

  

 

Maybe there are other genera or species that are a better match, but this is close enough for me I think.  Thanks for the help everyone!!

[MikeR]

Looks like the imprint of Manicina areolata.  LINK

Edited March 4 by MikeR

[digit]

Agreed! If I'd gotten home earlier I'd be the first to identify this as a negative imprint of a Manicinia areolata coral (instead of the last).

 

https://www.google.com/search?q="manicina+areolata"&tbm=isch

 

Young colonies of this species form a linear "zipper" type colony which over time expands into a more rounded hemispherical colony with more meandroid valleys. It's a commonly seen coral today in seagrass beds and sand flats adjacent to coral reefs (and often on the reefs themselves). If you look at some of the more linear colonies you can clearly imagine that the negative would match your mold.

 

 

Cheers.

 

-Ken

[ClearLake]

35 minutes ago, MikeR said:

Looks like the imprint of Manicina areolata

 

2 minutes ago, digit said:

Agreed! If I'd gotten home earlier I'd be the first to identify this as a negative imprint of a Manicinia areolata coral (instead of the last)

Yes, I see the similarity.  Thanks  I see some differences too, but unfortunately I know so little about corals, especially the more modern ones that I have no clue on variability within a species or the subtle differences between genera.  I thought it was pretty neat looking and since I didn't bring it home with me (wish I had) I am happy to go with the ID provided by those much more familiar.  And also, I can stop reading the 2012 paper: Taxonomic classification of the reef coral family Mussidae (Cnidaria: Anthozoa: Scleractinia) written by some friends of Ken before I get thoroughly lost in this interesting topic and get back to the Devonian.  

 

Thanks guys!!

[digit]

5 minutes ago, ClearLake said:

And also, I can stop reading the 2012 paper: Taxonomic classification of the reef coral family Mussidae (Cnidaria: Anthozoa: Scleractinia) written by some friends of Ken before I get thoroughly lost in this interesting topic and get back to the Devonian. 

It's a fun read if you wish to deep dive into that.

 

Corals can vary the shape of the colony depending on environmental factors (and space availability) as well as as they grow (ontologically).

 

Cheers.

 

-Ken

[digit]

There is actually one additional taxa that could be in contention. The small coral Meandrina areolata is very similar in form (and habitat).

 

https://www.google.com/search?q="meandrina+danae"&tbm=isch

 

The Manicinia colonies are distinctive by having a thin groove at the top of the ridge and having fairly broad deep valleys.

 

https://en.wikipedia.org/wiki/Manicina_areolata#/media/File:Manicina_areolata_(rose_coral)_(San_Salvador_Island,_Bahamas)_3_(16089935741).jpg

 

The septa (thin blades of the coral skeleton perpendicular to the ridges) are a bit more pronounced on the Meandrina and they alternate between higher and lower profile. It's probably difficult to tell what is going on in the reverse mold especially since it is difficult to see into the deeper parts which would correspond to the ridges in the living coral. Had you taken this home you'd be able to inspect closer. Surely, you had a spare suitcase in which to pack a huge rip-rap boulder?

 

https://commons.wikimedia.org/wiki/Category:Meandrina_danae#/media/File:FMIB_38205_Meandrina_danae_(M-Edw_&_H.jpeg

 

 

Cheers.

 

-Ken

[ClearLake]

11 minutes ago, digit said:

 

The Manicinia colonies are distinctive by having a thin groove at the top of the ridge

Yes, that is one thing I was struggling with since I saw that was an important feature.  I can't see the ridge top in "my" specimen.  Unfortunate.  If I would have just had a nice can of liquid latex with me!!!