"Fossil ball" - Campanian St. Bartholomä-formation, Gosau group, Eastern Alps

[FranzBernhard]

This time a really odd ball from St. Bartholomä, Styria, Austria (West of Kalchberg, point 36). Collected 04/09/2019.

Campanian St. Bartholomä-formation, Gosau group, Eastern Alps. 

The specimen was very dirty, thought it is just a round and smooth limestone piece, but haven´t found such a smooth piece there before, so I took it with me.

After cleaning (but without any prep) and inspecting with a hand lens, I discovered, that the subglobular specimen of about 7 cm in size is covered over and over with tiny polygons, about 0.1-0.2 mm in size. So it is a fossil! But what?

It seems to have two natural openings, a larger on (pic A) and a smaller one (pic B), with polygons all over the rims and also inside the rim of the opening (pic F). At the lower right corner of pic F you can see, that the polygons are in reality prismatic structures. Polygons are also covering large parts of the inside of the two openings. The prismatic structures can also be seen in some dimples caused by pressure solution.

Any hints and suggestions are welcome!

Many thanks!
Franz Bernhard

 

[abyssunder]

maybe a sponge?

[Bobby Rico]

I also think sponge like, a pretty cool find. 

[FranzBernhard]

16 minutes ago, abyssunder said:

maybe a sponge?

 

13 minutes ago, Bobby Rico said:

I also think sponge like

Thanks! Is it possible to narrow it down a little bit?

 

14 minutes ago, Bobby Rico said:

a pretty cool find. 

Indeed! Thought its just a piece of "limestone", but no-no, its more than that. And its a one-of-a-kind find, after about 500 rudists, 15 coral colonies etc...

Franz Bernhard

[Rockwood]

Agreed. I have a modern one from the Gulf of Maine that looks much like it setting on the side of the kitchen sink splash.

[Ludwigia]

I'm thinking sponge as well, but I can't think much further than that. They're often hard to identify anyway due to their extremely varied forms, even within one species.

[FranzBernhard]

@Ludwigia, @Rockwood, @Bobby Rico, @abyssunder,

Could this be something like Porosphaera?

 

There is a comprehensive paper about Porosphaera globularis, an abundant species in the European Campanian, but my specimen seems not to be this species.

https://www.degruyter.com/downloadpdf/j/agp.2015.65.issue-1/agp-2015-0005/agp-2015-0005.pdf

 

The openings could than be somewhat healed predation marks. And these sponges don´t have an attachment point (have found none in my specimen). 

 

There are some sponge experts here on TFF, would someone please tag them? Many thanks!

 

Franz Bernhard

[ynot]

@Spongy Joe, but he has not been logged in for awhile.

[FranzBernhard]

Thanks, @ynot!
Franz Bernhard

[abyssunder]

It doesn't look like the Porosphaera globularis specimens I have in my collection.

Maybe it's more close to the Camerospongia - Cystispongia line, but that's just an idea.

You need a sponge expert or someone from your area familiar with the Santonian - Maastrichtian sponge fauna, I'm affraid.

[FranzBernhard]

9 hours ago, abyssunder said:

Camerospongia - Cystispongia

Thanks! I have checked both - they look also somewhat different. The mystery remains.

 

I have contacted the author of this website, but the website was last updated more then 10 years ago:

http://www.cretaceous.de

 

Franz Bernhard

[abyssunder]

I've checked the referenced site before my first post, and I think our thoughts conduced to that.
The mystery of your specimen is still there in the Gosau sediments.
Hope someone will resolve that.

[HansTheLoser]

A polished section would be helpful. Sponge or Hydrozoa.

[FranzBernhard]

Thanks you very much for you opinion, @HansTheLoser!

Franz Bernhard

[D.N.FossilmanLithuania]

This sponge looks like chaetetid. The stromatoporata group of sclerospongians is typical not only to Paleozoic it is thought that they lived in Early Cenozoic too but Cretaceous chaetetid should be very rare case!

 

[FranzBernhard]

@D.N.FossilmanLithuania, I think, you got it!!

I have found this:

http://nik28289756.narod.ru/Chaetetida.html

Many thanks!
Franz Bernhard