Mystery mark on Devonian goniatite

[ScottBlooded]

The site I work most often (needmore formation in WV) produces a fair amount of what this forum has in the past generously identified for me as goniatites. I’ve noticed some with vaguely star shaped holes seemingly punched in them, although I’ve yet to have the chance to photograph one. Yesterday I came across this partial goniatite impression in situ with a really good example of what I’m talking about. Any ideas of what I’m looking at? It looks (to my amateur eyes) like something that occurred pre fossilization, and they always present just this way (overall star shaped with a penetrating circular hole in the middle, only on goniatite shells). As always thank you for your time.

[Rockwood]

I think this is a trace fossil. The home of a sponge would be a good place to start the research.

[Tidgy's Dad]

Possibly the mark left by a crinoid holdfast? 

[ScottBlooded]

1 hour ago, Rockwood said:

I think this is a trace fossil. The home of a sponge would be a good place to start the research.

I know literally nothing (as opposed to the usual next to nothing) about sponges, I wasn’t aware they made such shapes/anchored themselves to shells. I’ll research on early/mid Devonian sponges, but in my experience finding specific stuff can be a little time consuming. Any reading recommendations on the subject of sponges?

1 hour ago, Tidgy's Dad said:

Possibly the mark left by a crinoid holdfast? 

this makes sense, I guess I didn’t think about it because it’s so small but I’m guessing crinoids got pretty small too.

 

Whether sponge, crinoid or something else, I wonder why just the goniatites? Firing from the top of my head, they provide for a large, semi smooth flat surface, easier to anchor to. They’re also consistently the largest thing I find out there, so maybe just more of a chance you’d anchor to it than say a small brachiopod. Or is there something I’m missing?

[Tidgy's Dad]

Yes, some crinoids are quite small. 

Some species of animals evolve to attach themselves to other organisms when there is no suitable hard substrate. Some are generalists and some species specific. 

At this time many of the brachiopods were spiny or had marked growth lines and high ribs making it difficult for epibionts to attach to them. 

[ScottBlooded]

2 hours ago, Tidgy's Dad said:

Yes, some crinoids are quite small. 

Some species of animals evolve to attach themselves to other organisms when there is no suitable hard substrate. Some are generalists and some species specific. 

At this time many of the brachiopods were spiny or had marked growth lines and high ribs making it difficult for epibionts to attach to them. 

So there were species of crinoids that would exclusively anchor to specific things? Like specific types of shell and rock?

[Tidgy's Dad]

1 hour ago, ScottBlooded said:

So there were species of crinoids that would exclusively anchor to specific things? Like specific types of shell and rock?

I don't know about specific types of rock, and I'm not sure about crinoids in particular, but I do know of some bryozoans and inarticulate brachiopods that had favourite or sometimes specific hosts. 

[Ludwigia]

9 minutes ago, ScottBlooded said:

So there were species of crinoids that would exclusively anchor to specific things? Like specific types of shell and rock?

As far as I know not really. Their larva were mainly on the search for some kind of hard ground where they could anchor and often ended up using the shells of deceased molluscs among other things.

[ScottBlooded]

13 minutes ago, Ludwigia said:

As far as I know not really. Their larva were mainly on the search for some kind of hard ground where they could anchor and often ended up using the shells of deceased molluscs among other things.

This is kind of what I was thinking. Amongst the other available things that seem to present themselves in this part of this formation, the goniatites would seemingly present the most opportune landing pads. Also I suppose there’s a bit of observation bias for the same reasons, way easier for me to see on the comparatively large blank canvas of a goniatite. 

[Rockwood]

6 hours ago, Tidgy's Dad said:

Possibly the mark left by a crinoid holdfast? 

But wouldn't cliona borings cover the other holes with no need for one more step ?

[Tidgy's Dad]

1 hour ago, Rockwood said:

But wouldn't cliona borings cover the other holes with no need for one more step ?

I don't think that it looks like Cliona borings. And that family of boring sponges weren't about in the Devonian, I don't believe.