Protomelission

Protomelission is a Cambrian fossil taxon of contested affinity. It comprises cataphract arrays of box-like chambers, forming a club-shaped thallus surrounding a hollow central cavity. It was first described from phosphatized microfossils whose individual chambers were interpreted as housing the zooids of a non-mineralized bryozoan, which would make it the only affinity representative of that phylum – implying that all animal phyla originated in the Cambrian period. The subsequent discovery of articulated macrofossils from the Xiaoshiba biota called into question the biological nature of the distal apertures, showing that the surface was instead covered with leaf-like triangular flanges. This has led to the reinterpretation of the fossil material as a "seaweed", strictly as a dasycladalean green alga.