SEARCHING ECOMORPHOLOGICAL PATTERNS SHARED BY EXTANT UNGULATES AND EXTINCT XENARTHRANS. The scarce number of extant representatives of the Order Xenarthra offers a poor idea of the large morphological diversity that existed in the past. Because of this, the interpretation of the ecology of those extinct species is problematic. In order to understand the relationship between diet and habitat, the variability of the lower jaw of different mammals (mainly ungulates and xenarthrans) is analysed in this work by means of geometric morphometric methods. Using principal component and discriminant analyses, the main objective of this contribution is to find taxon-free ecomorphological patterns, which could be applied to extinct xenarthrans with the aim of inferring their ecology. Most part of the variance is due to the phylogenetic factor. However, part of the variability can be interpreted in ecological terms. Because of their characteristic craniodental morphology, glyptodonts occupy their own particular area of the morphospace. Vassallia maxima is proposed as a mix-feeder of mixed habitats, which agrees with previous results. For those sloth species which lower jaw is more similar to that of ungulates, discriminant analysis renders similar results to those obtained in the literature. On the contrary, sloth species with a more different morphology show results more coherent with previous studies by means of principal component analysis. The discriminant functions are not suitable to infer habitat in the Pleistocene mylodontids. Because ruminant species have a mandibular angle proportionally more developed for all diets, discriminant functions are not totally independent of phylogeny.