Exoconularia sp.
Conularid
Upper Ordovician
Maquoketa Formation
Pike County, Missouri, USA

67mm conularid on 75mm slab.

Exoconularia is a genus of conularid known from the Ordovician of Europe and North Africa..  Conularids (aka conulariids) are invertebrates that have been classified within the Phylum Cnidaria with which their bodies share fourfold symmetry but their skeleton is quite different from any cnidarian.  Some paleontologists suggest the known genera should be assigned to their own phylum.

Conularids were a long-lived group appearing in the Ordovician and dying out sometime in the Triassic.

Good example of an obscure extinct invertebrate.