Calathium | |
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Calathium formosum | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Porifera (?) |
Genus: | †Calathium Billings 1865 |
Calathium is an extinct genus of organism found in marine beds of Ordovician age. Its classification is enigmatic: It has long been placed among the receptaculites,[1][2] but it has also been described as a quasi-sponge,[3] possibly akin to the archeocyathids[4] or other hypercalcified sponge.[5] The chief difference from archaeocyathids is that their walls were connected by rods rather than septae.[4]
The organisms were important reef-forming organisms during the Ordovician, forming communities with lithistid sponges that gradually displaced the earlier microbial mounds.[4]