Worm tunnel casts

[KimTexan 1,718]

This is also from the North Sulfur River today. I think they are some type of cast of a worm tunneling, but it's only a guess. Anyone care to educate me a little more about what they are?

 

[KimTexan 1,718]

Here are a couple more. One is the flip side of the first pic. 

They're all a bit softer than most rock.

I didn't get the last one very clean. It was a bit more fragile and pieces were coming off when I was cleaning it.

 

[ynot 7,087]

They do look like burrow casts, maybe crab or shrimp.

[doushantuo 3,928]

Without implying anything about the crustacean nature or not :

edit:thinking Spongeliomorpha,possibly?

[KimTexan 1,718]

Ok I'm not familiar with shrimp or crab casts. Thanks. I'll try to see if I can find different types of casts pictures for that.

 

I assume the depths of the crevices or texture of the burrow differ by the type and maybe size of critter that made it. Is that correct?

An example is in the 3rd pic the far right one, it has a different texture than the others, especially if you compare it to the 2 in the previous pic.

[KimTexan 1,718]

3 minutes ago, doushantuo said:

Without implying anything about the crustacean nature or not :

I would not have recognized those on the right were a fossil at all! They look like amorphous blobs. Or I may have mistaken them for having been something that was weathered or tumbled along a creek/river bed or something.

[ynot 7,087]

There are thousands of extant species that burrow in the ocean beds, and each has it's own caricature. I would imagine the ancient oceans were much the same. (should also look for clam burrows.)

[doushantuo 3,928]

A lot of factors go into burrow morphology,among which is, of course,the nature of the tracemaker,as Tony pointed out.

However,burrowing as a behaviour has its energetic (physiological)limitations.

Especially in worms(polychaetes,echiurans).

edit:Tony's suggestion about a possible bivalve origin should be considered as well(compound Protovirgularia?)

 

[doushantuo 3,928]

crustacean burrows,why/how flowchart Source:authors to the very right of pic,journal: MEPS 128,1995

[doushantuo 3,928]

I liked "D" in this context(crustacean chimneys,not mentioned too often in ichnology(I think) leave a fossi record or not?)