Everyone on here is probably familiar with the old taxonomic ranks of kingdom, phylum, class, order, family, genus and species that was a mainstay of school biology classes and of course was a fundamental part of taxonomic work for, well, pretty much centuries. However, with the advent of cladistics more and more specific groupings of taxa were possible based on branching nature of phylogenetic trees. While there were sub-ranks of subfamilies, superorders, tribes and the like, these were rarely invoked and I think people shied away from them because they implied a level of detail that couldn’t really be inferred based on how these groups were generally formalised.
However, many of the intermediate ranks are rapidly falling by the wayside because they simply are no longer useful or don’t make sense. Kingdoms and phyla are still useful and major groups of taxa that represent fundamental divisions, and of course genera and species are the basis of all taxonomy, but that stuff in the middle? Doesn’t fit.
To take an excellent example (floated my way by Mike Taylor, despite the fact that it should have been obvious to me) birds are in Class Aves, we now accept that birds are dinosaurs but more specifically that means they sit within the traditional Superorder Dinosauria, Order Saurischia, Suborder Maniraptora and (depending on your favoured phylogeny / family definition) Family Paraves. So a Class ends up sitting in half a dozen groups that are supposed to be subordinate to it. And all the various orders and families of birds also sit in there. Oh.
We are increasingly getting close to building the Tree of Life – a single vast and unified trees that put whole phyla together at the species level in clades that most experts generally agree on. No longer are new or odd species somewhat arbitrarily assigned to families or have new families erected for them because they are special. We simply don’t think of trees and relationships in those terms anymore – not everything has to sit in a family, and it’s no longer the case that just a couple of researchers look at their clade and split up the taxa with no reference to related clades or other, wider patterns. As such, while at a conversational level, it still makes sense to use and discuss things like the ‘cat family’ or ‘dog family’ increasingly these are being abandoned for their formal names (Felidae and Canidae in this case) though the endings of various names betray their origins as the –idea, -inae, -oidea, and so on demonstrate. These now represent successive ranks rather than ‘families’ and ‘tribes’ as once they would.