Is S. hoffmani even a xeric sp.?Don't forget also there is a new world species Sphaerobothria hoffmani that has a small horn. I've dissected the horn on three Ceratogyrus species and I'm doubtful of the faster/expanded stomach hypothesis; the cavity is far too small to make a difference. What is really interesting about the horn is how far it goes into the body, not out of it.
No, I believe most of it's range is in Costa Rica and can't imagine it is hurting much for water. Like I said, the volume that even that largest horns can hold is pretty small when compared to the body. I really don't think the adaptive value has anything to do with the external horn; the movement of muscle and gut into that space is probably an aftereffect of the extension of the fovea.Is S. hoffmani even a xeric sp.?