Placental mammals consist of three main groups that diverged rapidly,evolving in wildly different directions: Afrotheria (for example, elephants and tenrecs), and Xenarthra (such as armadillos and sloths) and Boreoeutheria (all other placental mammals). The relationships between them bear been a subject of fierce controversy with multiple studies coming to incompatible conclusions over the last decade main some researchers to suggest that these relationships might be impossible to resolve.
Source: phys.org