What is this?

[Bringing Fossils to Life]

Found At Seven Stars PA a while ago, I am not sure weather this is a spine from the pygidium of a Greenops boothi, or if it is part of a phyllocarid telson. I am not an expert on arthropods, for all I know it could be a hyolithid (Hallotheca aclis). Adjacent fossil is a tiny gastropod, scale bar 5 mm.

Edited February 11, 2023 by Bringing Fossils to Life

[Rockwood]

It isn't the standard presentation, but I think it's a rugose coral. 

[Fossildude19]

Hyolith would be my guess.

 

[Bringing Fossils to Life]

It couldn't be a rugose coral, as they are not well preserved at Seven Stars and only a couple specimens are known from that site. I broke away some of the surrounding rock and it does seem to be a Hallotheca. Thanks for your help; I wouldn't have tried to break the rock if it were a phyllocarid!