Ciro Santilli Naming taxonomic ranks like genus, domain, etc. is a fucking waste of time, only useful before we developed molecular biology.
All that matters is the tree of clades with examples of species in each clade, and common characteristics shared by the clade.
And with molecular biology, we can build those trees incredibly well for extant species. When extinct species are involved however, things get more complicated.
There's six to eight in different systems of the end of the 20th century:
There's about 60 of them.