Fossils or just interesting concretions? Found in Big Brook, NJ

[TRexEliot]

Ordinarily I would throw something back if I didn't have at least a tentative ID when I saw it or some strong reason to believe it's a fossil, but this I really wasn't sure about. I have no idea what they might be, but I had never seen a concretion quite like them before in the brook, and I found it even more bizarre that I ended up finding two of them. Any thoughts?

 

 

 

 

Edited April 26, 2023 by TRexEliot

[hemipristis]

2 guesses: invertebrate coprolite or a chunk of a Calionassa sp. shrimp burrow. The latter are rather common in some of the late Cretaceous sediments in the Mid-Atlantic coastal plain of the US

[doushantuo]

Call me a nitpicker,but Calionassa would be a Nomen Misspellum

[TRexEliot]

Just going to jump in my old thread from a year ago to give the actual ID on this in case anyone stumbles onto this thread in the future looking for an answer to something similar. It's a piece of a cliona sponge (a sponge that bores into materials like shell).

[Carl]

Sorry: Neither of those look like Cliona. They most resemble Ophiomorpha, the burrow of callianassid shrimp, like Mesostylus, which is also found in the brooks. The first one might alternatively be a mass of invertebrate coprolites, but I think the match for Ophiomorpha is slightly better.

[TRexEliot]

@Carl cliona is the ID Ralph Johnson gave me for it, and it looks like some of the more worn cliona pieces I've found since. Can you explain why you think it isn't?

[Carl]

9 hours ago, TRexEliot said:

@Carl cliona is the ID Ralph Johnson gave me for it, and it looks like some of the more worn cliona pieces I've found since. Can you explain why you think it isn't?

Cliona has a very different structure from Ophiomorpha. Cliona is a series of interconnected, 3-dimensionally arranged tunnels (see here: https://fossilsofnj.com/invertebrates/cliona_cretacica.htm), whereas Ophiomorpha is a collection of similar-sized, spherical pellets creating a single surface (see here: https://www.fossilsofnj.com/invertebrates/ghost_shrimp.htm).

[TRexEliot]

@Carl thanks, I see what you're saying.