It’s no secret that Euphyllia corals are a very diverse group and it seems that some of these species may be more different from each other than we ever thought. We see both a range of forms within each of the species and plenty of ‘frogs-torches’ and ‘ham-spawns’ that have an intermediate appearance between the classically recognized species.
Once upon a time the various Euphyllia were classified into two subgenera – Euphyllia for the ‘phaceloid’ or branching torch, branching hammer, branching frogspawns etc. (E. glabrescens, E. cristata, E. paraancora, E. paradivisa, and E. paraglabrescens). Meanwhile a separate genus, Fimbriaphyllia, was used to contain the ‘wall’ corals like ‘classic’ hammers (E. ancora) and normal frogspawns (E. divisa).
As new species with intermediate growth forms were discovered and classified the two subgenera were lumped into one but new research into this group is aiming to clarify their relationship with the resurrection of Fimbriaphyllia to a full genus status.
This time around the taxonomy of the Euphyllia is drilling down deeper than just purely the shape of the skeleton and accounting for genetic analysis as well as the shape and especially the length of the polyp and spawning behavior. The typical branching Euphyllia are hermaphroditic brooding corals – this explains why we see so many tiny babies released from torch corals – while the regular hammer & frogspawn corals are broadcast spawners with separate sexes.
This somewhat helps to explain why it’s possible to group most Euphyllia corals close together in aquaria but have to keep torch corals isolated so it doesn’t light up its congeners. The proposal to resurrect Fimbriophyllia seems to be based on a lot of sound observations but as Joe Rowlett pointed out, there might be some issues with using this particular genus name.
Just as when we discovered that Galaxea and Euphyllia are more closely related than we ever knew, it’s equally enlightening to learn that some of the Euphyllias are more different than we ever imagined, but having different spawning behavior is a pretty big one. The research paper is a dense read but if you want to dive into the deep end of Euphyllia taxonomy, Katrina Luzon et. al. will keep you busy for a little while.