Body mass estimation of Quaternary proterotheriids (Mammalia, Litopterna) and description of a new specimen of Neolicaphrium recens Frenguelli, 1921. A body mass estimation for Quaternary specimens of the family Proterotheriidae was performed using predictive regression equations for extant ungulates. A body mass of 20 –40 kg for Neolicaphrium recens and of <70 kg for Uruguayodon alius are determined based on the analysis of dental, mandibular, and postcranial dimensions including lengths, areas, and volumes. This study incorporates estimates obtained through measurements of elements of the appendicular skeleton, humerus, tibia and astragalus. Limb bones are directly related to body support and locomotion, and therefore their measurements are better estimators of body mass than craniodental dimensions. Additionally, is described and studied a new material of N. recens exhumed from Pleistocene deposits of Colonia Department, southwestern Uruguay.