Afrotherian affinities for endemic South American “ungulates”

The phylogenetic relationships of endemic South American ungulates are a highly debated topic. Among them, the most well-known clades are the Notoungulata and the Astrapotheria. Three unambiguous hard-tissue features characteristic of afrotherian mammals potentially indicate a relationship with the two South American clades: delayed cheek-tooth replacement, more than 19 thoracolumbar vertebrae, and the presence of a well defined astragalar cotylar fossa. New data based on many fossil specimens preserving deciduous dentition and a morphometric assessment of those specimens, together with a revision of available postcranial anatomy in relevant fossils are used to examine the distribution of the three characters in placental phylogeny.