Liarthrus ("smooth joint")[1] is a genus of astrapotheriidmammal known from the Late Oligocene (DeseadanSALMA, around 29–21 mya) Sarmiento Formation of Santa Cruz Province, Argentina.[2][1] It was described by the Argentine paleontologistFlorentino Ameghino in 1895 along with several other genera from the "Pyrotherium Beds", which were then believed to date to the Cretaceous period.[3] Ameghino described Liarthus on the basis of fragmentary, being only a right astragalus (tarsal bone), premolar 4, and an incomplete premolar from the upper jaws.[4][2] Only one species was described, L. copei, the species name honoring the American paleontologist Edward Drinker Cope, who lived during the same interval as Ameghino. Liarthrus was synonymized with the other astrapothere Parastrapotherium in 1914 by American mammalogistFrederic Loomis,[5] though it was revalidated by a 2008 analysis of Parastrapotherium.[2]Liarthrus was a herbivorous mammal, being an astrapothere, which had large tusks on their skulls and mandibles in addition to a large body size.[6]
