Symbiotic endobionts in Paleozoic stromatoporoids

• Earliest symbiotic endobionts in stromatoporoids appear in the Hirnantian.
• Cornulitids were the only stromatoporoid symbionts in the Ordovician.
• Rugosans dominated Silurian symbiotic associations.
• Syringoporids dominated Devonian symbiotic associations.

Stromatoporoids hosted a diverse fauna of symbiotic endobionts during the Silurian and Devonian. Assemblages of symbiotic endobionts from the Ordovician, Silurian and Devonian differ significantly. The only symbiotic association in the Ordovician is cornulitid-stromatoporoid. The diversity of Silurian and Devonian symbiotic associations is similar, but the taxonomic compositions of the Silurian (i.e. rugosans, syringoporids, cornulitids, lingulids, Chaetosalpinx and Helicosalpinx) and Devonian (i.e. syringoporids, Torquaysalpinx, Chaetosalpinx, Streptindytes, and rugosans) associations are different. Symbiotic corals dominated both Silurian and Devonian associations, rugosans dominated the Silurian associations, and syringoporids dominated the Devonian associations.