Conulariidae

Conulariida are an extinct group of medusozoan cnidarians known from fossils spanning from the latest Ediacaran up until the Late Triassic. They are almost exclusively known from their hard external structures (alternatively referred to as a theca, periderm or test), which were pyramidal in shape and made up of numerous lamellae (thin layers). They are thought to have been sessile animals that grew with the narrower tip anchored to the seafloor, with the wider end bearing an array of tentacles used to ensnare prey.

==Structure== The conulariids are fossils preserved as shell-like structures made up of rows of calcium phosphate rods, resembling an ice-cream cone with fourfold symmetry, usually four prominently-grooved corners. New rods were added as the organism grew in length; the rod-based growth falsely gives the fossils a segmented appearance. Exceptional soft-part preservation has revealed that soft tentacles protruded from the wider end of the cone, and a holdfast from the pointed end attached the organisms to hard substrate. The prevailing reconstruction of the organism has it look superficially like a sea anemone sitting inside an angular, hard cone held perpendicular to the substrate. Conulariid shell is composed of francolite with carbonate ion concentration 8.1 wt%. The lattice parameters of conulariid apatite are a = 9.315(7) Å, c = 6.888(3) Å. The fine structure of their shell comprises multiple lamellae of alternately organic-rich and organic-poor layers.