What The Fossil?

[I_gotta_rock]

Found this in Big Brook, NJ (Late Cretaceous Navesink Fm.). It's about 2.5 cm wide. I don't even know what phylum to put it in. My first thought was bryozoan. There is one very thorough paper on Bryozoa of the Atlantic Coastal Plain, but it has nothing to fit the bill. Looks like sponge with those big holes. Found a picture of Discopora sp. that looks very close, but that genus is not listed in PBDB anywhere in North America. Gabb thought he had something similar from NJ, but it turned out to be a sand concretion. The last picture is the underside of the specimen, which may or may not be a thin layer of shell material from a bivalve.

 

Edited May 4, 2022 by I_gotta_rock

[bthemoose]

Maybe a bryozoan?

[Jeffrey P]

That looks more like a bryozoan to me and if that's the case, it is an exceptional specimen for BB. Congrats!

[Rockwood]

7 hours ago, I_gotta_rock said:

Bryozoa of the Atlantic Coastal Plain

This need not be from the here. Glacial imports from higher ground to the north show up in the brooks now and then.

[Ludwigia]

How about a sponge?

[I_gotta_rock]

4 hours ago, Rockwood said:

This need not be from the here. Glacial imports from higher ground to the north show up in the brooks now and then.

Indeed. I have also considered that it could have been carried in from deeper water at that time or transported in some fossil hunter's backpack. The problem of identification remains, though.

[DPS Ammonite]

Are the structures visible in cross section? A fundamental difference between sponges and bryozoan is that the chambers of bryozoan are discrete and separate. The chambers of a sponge interconnect to allow for water flow. I can’t see any interconnecting chambers in your photos. Do you see any?

[I_gotta_rock]

21 minutes ago, DPS Ammonite said:

Are the structures visible in cross section? A fundamental difference between sponges and bryozoan is that the chambers of bryozoan are discrete and separate. The chambers of a sponge interconnect to allow for water flow. I can’t see any interconnecting chambers in your photos. Do you see any?

Yes, I was looking for that, too, but it is unbroken all the way around and I'm loathe to mess up such a nice specimen.

Another way to tell is that sponges are, as a whole, tubes. I have seen some that did not consistently have tube openings at the top, most notably Discodemis, This does have some holes in places. One looks like a broken gastropod, but the others aren't.

[I_gotta_rock]

Update: I've been making inquiries through more direct channels. This is a bryozoan colony. It's not in the old books.  It is not one of the ones identified in the most recent, and rather extensive paper I could find on "Bryozoa of the Atlantic Coastal Plain," which includes TN and MS. and some localities in Europe I contacted the author and he confirmed that it's not one he listed. He said it was a Cyclostomate Bryozoan, but couldn't be more specific. I contacted the Smithsonian's invertebrate curator. He doesn't know. I contacted the Monmouth (New Jersey) Amateur Paleontological Society's museum. They don't have any of these. I'd just let it go, but this is about as well-preserved a specimen as anyone could ask for and everyone is stumped, so now I can't let it go. If anyone out there knows any Cretaceous bryozoa experts who might be inclined to help find a name for it or describe it, I'd be much obliged for contact info. I have access to a research-grade microscope again, so I can get better microphotos. 

[Sjfriend]

Good luck and keep us updated. Always great to to get a problem answered!

[abyssunder]

My first thought was something along a bryolith.

Maybe something similar to the specimen of the top of this picture?

 

 

Edited June 2, 2022 by abyssunder