-BODY MASS ESTIMATION OF A QUATERNARY SPECIMEN OF THE EXTINCT CAPYBARANEOCHOERUS THROUGH CRANIODENTAL MEASUREMENTS. An estimated body mass of a specimen of Neochoerus Hay cf. N. aesopi (Leidy) (Mammalia, Rodentia, Hydrochoeridae) from the Quaternary of Uruguay was made based on craniodental measurements. Regression equations used to estimate the mass of other fossil rodents were applied. A value reference was also calculated by scaling of a specimen of the extant Hydrochoerus hydrochaeris (Linnaeus). In this study it is estimated that this extinct rodent may have reached a three times bigger mass than an extant capybara.Key words: Neochoerus, capybara, rodent, body mass, regression.RESUMO -Com base em medidas crânio-dentárias foi realizada uma estimativa da massa corporal de um espécime de Neochoerus Hay cf. N. aesopi (Leidy) (Mammalia, Rodentia, Hydrochoeridae) do Quaternário do Uruguai. Foram aplicadas equações de regressão que têm sido empregadas para a estimativa de massa de outros roedores fósseis. Além disso, foi calculado um valor de referência pelo escalonamento de um espécime atual de Hydrochoerus hydrochaeris (Linnaeus). No presente estudo se estima que este roedor extinto possa ter alcançado uma massa corporal três vezes maior do que a da capivara atual. Palavras-chave:Neochoerus, capivara, roedor, massa corporal, regressão.

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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.

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