Archaeolithophyllum

Archaeolithophyllum is a genus of conceptacle-bearing red alga that falls in the coralline stem group. It somewhat resembles "Lithophyllum."
As of today, "Archaeolithophyllum" is the only Palaeozoic coralline to bear clear conceptacles, although the earlier "Graticula" does bear reproductive structures.
It mineralized using aragonite. Its conceptacles are cone-shaped protrusions that extend outwards from the thallus surface and have a single central opening. It probably encrusted muddy or sandy surfaces.