Data from: Biodiversity dynamics and environmental occupancy of fossil azooxanthellate and zooxanthellate scleractinian corals

Scleractinian corals have two fundamentally different life strategies,
which can be inferred from morphological criteria in fossil material. In
the non-photosymbiotic group nutrition comes exclusively from
heterotrophic feeding, whereas the photosymbiotic group achieves a good
part of its nutrition from algae hosted in the coral’s tissue. These
ecologic differences arose early in the evolutionary history of corals but
with repeated evolutionary losses and presumably also gains of symbiosis
since then. We assessed the biodiversity dynamics and environmental
occupancy of both ecologic groups to identify times when the evolutionary
losses of symbiosis as inferred from molecular analyses might have
occurred and if these can be linked to environmental change. Two episodes
are likely: The first was in the mid-Cretaceous when non-symbiotic corals
experienced an origination pulse and started to become more common in
deeper, non-reef habitats and on siliciclastic substrates initiating a
long-term offshore trend in occupancy. The second was around the
Cretaceous/Paleogene boundary with another origination pulse and increased
occupancy of deep-water settings in the non-symbiotic group. Environmental
factors such as rapid global warming associated with mid-Cretaceous anoxic
events and increased nutrient concentrations in Late Cretaceous–Cenozoic
deeper waters are plausible mechanisms for the shift. Turnover rates and
durations are not significantly different between the two ecologic groups
when compared over the entire history of scleractinians. However, the
deep-water shift of non-symbiotic corals was accompanied by reduced
extinction rates, supporting the view that environmental occupancy is a
prominent driver of evolutionary rates.