BODY MASS ESTIMATIONS IN LUJANIAN (LATE PLEISTOCENE-EARLY HOLOCENE OF SOUTH AMERICA) MAMMAL MEGAFAUNA

Abstract

In this paper a data base is initiated, with the body mass estimations for a number of xenarthran and epitherian species of the Lujanian Land Mammal Age (late Pleis- tocene - early Holocene of South America). For doing that, a set of allometric equations was used, which had been previously developed from craniodental and limb bone dimensions in modern mammals. The results were analysed statistically. The dispersion of body mass estimations was remarkable in the totally extinct xenarthran groups. Certain measurements (particularly, the posterior jaw length in glyptodonts and the transverse diameter of the femur in ground sloths) gave spurious predictions relative to non-xenarthran mammals. New equa- tions specifically for xenarthrans should be developed to use these measurements. The dispersion of the epitherian mammals was lower than in the studied xenarthran. It is sug- gested that arithmetic mean should be used in those studies in which large size is the conservative hypothesis, and another statistic (such as the geometric mean, median or mode) in the opposite case. This database is intended to be the starting point for many autecological and synecological studies of this extinct fauna.