Agnostid?

[Pseudogygites]

I found this fossil a few days ago at an exposure of the Billings Shale. It was found associated with Triarthrus glabellas and brachiopods. It's structure leads me to believe that it's either an Isotelus pygidium or an agnostid, although I do not know of any agnostics described in this formation and age.

[Innocentx]

It looks like the Cambrian Rhastagnostus but of course wrong time period. Though I didn't find your guy here, this is a fun resource:  

https://www.amnh.org/our-research/paleontology/paleontology-faq/trilobite-website/gallery-of-trilobites/ordovician-period-trilobites

 

 

[Tidgy's Dad]

What is the size of this, please? 

[Fossildude19]

This actually looks like a disarticulated/broken Triarthrus trilobite cephalon, to me.   

[Pseudogygites]

11 minutes ago, Fossildude19 said:

This actually looks like a disarticulated/broken Triarthrus trilobite cephalon, to me.   

One park of it does look like a Triarthrus glabella. Could the larger flat plate beside it be the ventral side of the cephalon?

Thanks for the info!

[Fossildude19]

It could be. Not sure, ... maybe @piranhacan make sense of it.

[Innocentx]

14 hours ago, Fossildude19 said:

This actually looks like a disarticulated/broken Triarthrus trilobite cephalon, to me. 

I see what you're saying, especially in the top photo. The right side is intact and the left side is gone.