It is widely agreed that this broad group should be subdivided into three or four subgroups, but the level at which this should be done, and exactly which species should be grouped together, remain unclear.
Der er bred enighed om, at denne brede gruppe bør underdeles i tre eller fire undergrupper, men det er stadigvæk uklart, hvilket plan adskillelsen skal ske på, og hvilke arter der skal grupperes sammen.