conulariid

Conulariids were a group of extinct marine invertebrates that lived from the Cambrian to the Triassic periods. Their exact taxonomic placement has been a subject of debate, with some researchers considering them cnidarians, related to modern jellyfish and corals, while others have proposed alternative classifications. Conulariids possessed a distinctive, conical or pyramidal exoskeleton, typically made of chitinophosphatic material. This shell was generally four-sided and divided internally by transverse partitions called diaphragms.

The external surface of the conulariid shell was often ornamented with a series of fine, transverse ridges or growth lines, and sometimes with longitudinal ribs. They are thought to have been sessile, attaching to the seafloor or other objects, or possibly free-swimming, using their shells for buoyancy. The living animal likely occupied the apical (pointed) end of the conical shell, with its soft tissues extending out. Their diet is presumed to have consisted of small planktonic organisms, captured using tentacles. Fossils of conulariids are found worldwide in marine sedimentary rocks. The complete disappearance of conulariids at the end of the Triassic marks the end of their long evolutionary history.