Taxonomic and ecological assessment of an Antarctic Eocene Folivora (Mammalia) metacarpal using three‐dimensional geometric morphometrics

Here, we reassess the taxonomic affinities and functional morphology of TMM 44190-1, an isolated metacarpal II from the Eocene La Meseta Formation, Marambio (Seymour) Island, Antarctic Peninsula, previously referred to an indeterminate xenarthran. We evaluated its morphological similarities using three-dimensional geometric morphometrics. A principal component analysis, based on a sample of 50 metacarpals representing 38 taxa, including Paleogene terrestrial mammals from Antarctica and South America, as well as extant mammals exhibiting a wide range of terrestrial locomotor habits, was conducted. Additionally, TMM 44190-1 was compared with Eocene taxa from Antarctica and South America, including Gondwanatheria, Metatheria (Sparassodonta, Pucadelphyidae, and Didelphimorphia), South American native ungulates (Astrapotheria, Litopterna, Xenungulata, and Notoungulata), and Xenarthra (Cingulata and Pilosa). Both geometric morphometric and qualitative anatomical evidence consistently support the previous assignment of TMM 44190-1 to Xenarthra and further allow a more precise taxonomic placement, identifying the specimen as an indeterminate Folivora.