Data from: Ancient collagen reveals evolutionary history of the endemic South American ‘ungulates’

Since the late eighteenth century, fossils of bizarre extinct creatures
have been described from the Americas, revealing a previously unimagined
chapter in the history of mammals. The most bizarre of these are the
‘native’ South American ungulates thought to represent a group of mammals
that evolved in relative isolation on South America, but with an uncertain
affinity to any particular placental lineage. Many authors have considered
them descended from Laurasian ‘condylarths’, which also includes the
probable ancestors of perissodactyls and artiodactyls, whereas others have
placed them either closer to the uniquely South American xenarthrans
(anteaters, armadillos and sloths) or the basal afrotherians (e.g.
elephants and hyraxes). These hypotheses have been debated owing to
conflicting morphological characteristics and the hitherto inability to
retrieve molecular information. Of the ‘native’ South American mammals,
only the toxodonts and litopterns persisted until the Late
Pleistocene–Early Holocene. Owing to known difficulties in retrieving
ancient DNA (aDNA) from specimens from warm climates, this research
presents a molecular phylogeny for both Macrauchenia patachonica
(Litopterna) and Toxodon platensis (Notoungulata) recovered using
proteomics-based (liquid chromatography–tandem mass spectrometry)
sequencing analyses of bone collagen. The results place both taxa in a
clade that is monophyletic with the perissodactyls, which today are
represented by horses, rhinoceroses and tapirs.