Mystery Fossil

[TulsaPllTbFndr]

My buddy found this fossil recently while searching the river. We aren't really sure what kind it is. Is there anyone with some fossil knowledge that could offer us some insight?

 

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[SnakemanBill]

appears to be a trilobite

 

[Red-Coat]

Well, at first glance what it most resembles is the cast of a trilobite burrow. This is not a fossil of the trilobite itself, but the result of fine sediment infilling a hole it left behind and then lithifying. These can either be compact and slug-like as "resting burrows" (Rusophycus), or as continuous trails representing "feeding burrows" in sediment (Cruziana). There is a third kind made by movement of trilobite appendages on the surface of sediment (Diplichnites). These are a mixture of the first two types.



The three terms Rusophycus, Cruziana and Diplichnites are what we call 'ichnogenus' categories. We can't determine the actual genus or species of the animal that produced the traces, so we invent a genus which is characterised only by shape and appearance. Before exploring that possibility (or other possibilities) it would be good to have a more specific location. The deposits from which it came would of course need to be marine and at least before the end of the Permian (roughly 250 million years) and ideally before the end of the Devonian (roughly 350 million years).

 

[TulsaPllTbFndr]

Thank you very much for taking the time to give me such an in-depth and informative answer. I really appreciate that. Very interesting too! You must have some kind of background in this type of stuff. Does your profession involve this kind of thing or is it just a personal interest? Thx again!

 

[Red-Coat]

Thank you very much for taking the time to give me such an in-depth and informative answer. I really appreciate that. Very interesting too! You must have some kind of background in this type of stuff. Does your profession involve this kind of thing or is it just a personal interest? Thx again!

You’re most welcome. My interest in fossils is lifelong but not as a career. I started collecting when I was nine and I’m sixty-six now. I have several trilobite resting burrows but nothing like as detailed as yours. It’s a really nice specimen.

You didn’t answer the question of a more specific location so I’m still going with that ID based on the assumption you found it near Tulsa, Oklahoma. The geology would be consistent since Tulsa County and the area around Tulsa itself have marine deposits of the correct age. The county’s surface deposits span the Des Moinesian (313.8 - 305.9 million years) and the Missourian (305.9 - 303.4 million years). To the west of Tulsa, the underlying strata are Permian through to more recent. To the East, there are older Mississippian, Devonian and Silurian strata all the way back to 443.8 million years.

 

[TulsaPllTbFndr]

Sorry, it took me so long to respond! Have been busy with work lately. Yes, it was found in the Arkansas River here in Tulsa County. Sorry, I totally forgot to tell you the location. For being into fossils that long you must have a really nice collection. What a great hobby/interest. You sound well read.

 

[Red-Coat]

Sorry, it took me so long to respond! Have been busy with work lately. Yes, it was found in the Arkansas River here in Tulsa County. Sorry, I totally forgot to tell you the location. For being into fossils that long you must have a really nice collection. What a great hobby/interest. You sound well read.

Thanks. Yes it's now quite a collection and it's not the only thing I collect. I guess you know what you know based on your interests. By contrast I'm never going to be much help identifying American tractor parts or Civil War militaria.

 

[TulsaPllTbFndr]

Hey, sometimes it's best to have expertise in just a few areas rather than be a novice in many. A guy can get spread too thin if he's not careful!