A symbiosis between bryozoans and the tabulate coral Cladochonus in the Devonian

Symbiotic (mutualistic) relationships are hypothesized for species of the tabulate coral genus Cladochonus McCoy, 1847 associated with trepostome and cryptostome bryozoans in the Devonian. The species Cladochonus isaacmariai n. sp. from the Birdsong Shale (Lower Devonian, middle Lochkovian) of Tennessee, USA, was an obligatory symbiont of the trepostome bryozoan Nakremella symbiotica n. gen. n. sp. Cladochonus sp. A and Cladochonus sp. B from the Givetian (Middle Devonian) of Sauerland, Germany, are intergrown with the cryptostome species Intrapora variabilis Ernst, 2008. This interrelation is interpreted to be obligatory for the coral and facultative for the bryozoan. The coral symbionts benefitted from the bryozoans due to the enhanced mechanical stabilisation and enhanced feeding, while the bryozoans benefitted from the provision of a substrate, access to the higher tiering (arborescent growth), and receiving protection from the corals.