zuzu says that list is in order of species;
KentPfeiffer says the same list is in order of genus.
In the alphabet, S comes after H, P, O and R. Too bad for me, I guess I will just have to get over it.
I once moved to a town where the residents gave directions by saying,
"Turn left where Sears used to be and then turn right where JCPenney was."
Those directions were no help to me as I was a new resident and had no knowledge of the former locations of those two stores.
At the moment I feel the same way about the 'alphabetical' list which assumes I know something that used to be true.