Symbiosis in corals of the Devonian
https://www.mpg.de/23637516/coral-devonian-photo-symbiosis?c=12641503Analysis of nitrogen isotopes by a team lead by the max Planck Institute for Chemistry provides evidence of the earliest known photosymbiosis in corals of the devonian.
analysis to demonstrate that 385 million years old corals of the Devonian from the Eifel